- The Aerospace Corporation

Transcription

rosslink
C
®
The Aerospace Corporation magazine of advances in aerospace technology
Fall 2014
Pushing the
Boundaries
of Space
Crosslink
IN THIS ISSUE
Fall 2014 Vol. 15 No. 1
Departments
4
2 PROFILE
Margaret Chen
30
Technology and Innovation:
The Key to New System Development
Sherrie L. Zacharius
RESEARCH HORIZONS
A technology-focused culture of innovation is essential for the
national security space enterprise to succeed.
36BOOKMARKS
56CONTRIBUTORS
60
6
BACK PAGE
Crosslink
Think Big, Fly Small
Charles L. Gustafson and Siegfried W. Janson
The increasing popularity and functionality of small satellites has
helped them move beyond technology demonstration and into the
realm of commercial and governmental applications.
®
The Aerospace Corporation magazine of advances in aerospace technology
Fall 2014
Pushing the
Boundaries
of Space
12
Internal Research and Development Spurs
Advancements and Fills Technology Gaps
T. Paul O’Brien
On the cover: Susan Crain, research engineer, Space
Instrumentation Department, holds a dosimeter built
in the Aerospace laboratories in 1997 that weighed
3.63 kilograms (8 pounds) and used 4.5 watts of
power. The miniature dosimeter she holds was developed at Aerospace and licensed to Teledyne in 2009.
It weighs 20 grams (.044 pounds) and uses less
than 0.28 watts of power.
Aerospace internal research has led to real-world components
that vastly miniaturize space environment sensors.
18
2025 and Beyond: The Next Generation
of Protected Tactical Communications
Jo-Chieh Chuang, Joseph Han, and Bomey Yang
Visit the Crosslink Web site at
www.aerospace.org/publications/crosslinkmagazine
Copyright © 2014 The Aerospace Corporation. All rights reserved. Permission to copy or reprint is not required, but appropriate credit must be given to Crosslink and The Aerospace
Corporation.
All trademarks, service marks, and trade names are the
property of their respective owners.
Crosslink (ISSN 1527-5264) is published by The Aerospace
Corporation, a California nonprofit corporation operating a
federally funded research and development center that provides objective expertise, analysis, and assessments in multiple markets, including for government, civil, and commercial
customers.
For more information about Aerospace, visit www.aerospace.org or write to Corporate Communications, P.O. Box
92957, M1-447, Los Angeles, CA 90009-2957.
Questions or comments about Crosslink may be sent via
e-mail to [email protected] or write to The Aerospace Press,
P.O. Box 92957, Los Angeles, CA 90009-2957.
Developing affordable, protected, and interoperable satellite
communications systems are goals of tomorrow’s space
and ground architectures.
26
Applying Systems Engineering to Manage
U.S. Nuclear Capabilities
Matthew J. Hart, James D. Johansen, and Mark J. Rokey
The Aerospace Corporation’s expertise in program systems engineering and integration is being applied to nuclear programs for the
National Nuclear Security Administration.
From the Editors
This issue of Crosslink showcases some of the next-generation
technical developments the company is pursuing and how these are
being applied to The Aerospace Corporation’s customers and their
space system programs.
The magazine presents a sample of the breakthrough technologies
that are changing the landscape of possibilities for solving some of
the toughest challenges in space today. In an era of cost constraints
and reduced budgets, it is essential that Aerospace offer a leadership role to its customers in understanding these technologies, so
that the national security space community can choose from the
best solutions available to complex and varied issues.
Small satellites, miniature space sensors, next-generation communication architectures—these and more are explored. Much of this
work is happening in the laboratories, where Aerospace scientists
and engineers push the boundaries of what is known, plot out the
testing of new findings and theories, and explore whether what is
discovered on Earth can be applied to space. Collaborating with
other scientists and engineers throughout the world via symposiums, conferences, workshops, and the presentation of published
papers helps ensure Aerospace remains a key player in the space
community.
Aerospace innovation goes beyond the laboratory to include systems engineering and integration. For example, the corporation is
now providing the National Nuclear Security Administration with
independent assessments and novel approaches in these areas, as
well as with its risk management practices and procedures.
Aerospace has a long history of having its feet firmly planted in
research and development. There is a renewed focus on this today,
as the corporation actively seeks to emphasize the value that comes
from investing in innovation and cultivating such a culture within
its workforce. We hope this issue offers you insight into some of the
company’s current efforts and work focus in this arena.
Courtesy of United Launch Alliance
Crosslink is published by The Aerospace Press. Its
founding organization, The Aerospace Institute,
is celebrating its 20-year anniversary in 2014.
CROSSLINK FALL 2014
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PROFILE
Margaret Chen, Associate Director, Space Sciences Department
Mission Assurance
for the Space
Environment
Margaret Chen has honed expertise in nearEarth space and the magnetospheric environment
during a career spanning 22 years at Aerospace.
By Nancy Profera and Richard Park
M
argaret Chen began her career at The Aerospace
Corporation as a National Research Council postdoctoral associate developing a new physics-based
simulation model of Earth’s ring current for studying magnetic storms. She has since performed research on chargedparticle transport, acceleration, and loss, and wave particle
interactions in Earth’s magnetosphere and ionosphere. Chen
has also developed expertise in creating computer simulation models to better understand these space environment
phenomena and their potential effects on satellites.
Born and raised in Southern California, Chen grew up
in a supportive and scientifically oriented environment. Her
parents each earned science degrees, her mother in physics
and computer science, and her father in electrical engineering. Her father began his career as an electrical engineer
working at Ford Philco, and then later formed his own business that included food services and real estate. After being
a stay-at-home mom for sixteen years, Chen’s mother went
into the workforce. She started by managing a few of her
husband’s business projects and then ventured into a career
as a computer software developer and technical manager
for Toshiba of America. “My parents taught me to be an
independent thinker. They also taught me the importance of
developing a career with work that I was passionate about,”
said Chen.
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Chen chose science as her own career, earning a bachelor’s degree in physics and graduating magna cum laude
from the University of California, Irvine, in 1984. She then
enrolled in a physics Ph.D. program at the University of California, Los Angeles. There, she met advisor and Professor
of physics and astronomy, Maha Ashour-Abdalla, who was
working on space science simulation efforts. “The work was
very interesting to me, and that’s how I got started in space
science research,” said Chen. “My graduate studies were in
plasma physics, and the environment of space is 99 percent
plasma, so it was definitely a good fit for me.” Her advisor
collaborated with James Roeder, director of the Space Sciences Department, and that is how she learned about job
opportunities at Aerospace.
During the course of her career, Chen has been awarded
more than 15 National Science Foundation and NASA
research grants. She has written 50 journal articles, given
31 invited conference presentations, and contributed to
166 other presentations. The research topics include understanding the ring current, diffuse aurora, and plasma sheet
dynamics during magnetic storms. She has recently added
magnetosphere-ionosphere-thermosphere coupling to her
research interests. Chen has also served as an editor for
Geophysics Research Letters. In 2013, she was a recipient of
Aerospace’s Woman of the Year award, recognized for her
contributions as the principal investigator of several independent research and development proposals, and for her
efforts in the broader scientific community.
to today’s space environment events, and this helps us to
determine whether recent Milstar satellite upsets are out of
character, or within the expected limits of the dynamic space
environment,” said Chen. Her work in this area also helps
Space Science Research
Aerospace and the U.S. government address space environment issues for future GEO spacecraft.
As associate director of the Space Sciences Department at
Chen’s role at Aerospace also involves strategic business
Aerospace, Chen explained, “We perform research on the
planning, as well as mentoring and guiding younger staff
near-Earth space environment and apply that knowledge to
members. The department regularly submits proposals to
our customers’ needs. This helps us to prepare satellites and
NASA and the National Science Foundation for grants and
launch vehicles for the environmental effects they will face
new work. Funding for research in the space sciences has
on their space systems.” The department’s current work is
been decreasing, while securalso focused on understanding those funds is tougher and
ing ionospheric effects and
Being involved in the scientific community and
increasingly competitive. To
propagation, anomaly resolution, and threat analysis. Most
gaining exposure through leadership positions is address this challenge, Chen
believes Aerospace must continue
recently, Chen has been able
essential. It conveys that we are active players in to engage and participate in the
to apply her space environscientific community.
ment knowledge to the NASA
the research community.
“One of the areas Aerospace
Two Wide-angle Imaging
has been successful in is our pubNeutral-atom Spectrometers
lishing papers, being on national and international leader(TWINS) mission. The purpose is to gain a global view
ship committees, organizing and attending conferences, and
of the dynamic inner magnetosphere, the area of space in
writing proposals for research grants. Being involved in the
which charged particles are controlled by Earth’s magnetic
scientific community and gaining exposure through leaderfield. Chen is the Aerospace program manager for this effort,
ship positions is essential. It conveys that we are active playand also a member of the TWINS science team. The work is
ers in the research community,” said Chen.
done in collaboration with the Southwest Research Institute,
When thinking about the future, Chen sees an emergwhich built the onboard instruments for data operations.
ing trend of further collaboration among the space sciMeanwhile, Aerospace personnel built many of the sensors
ences community. For example, it has become increasingly
on board. “It is exciting in that the space environment data
clear that one model is no longer sufficient for space-based
we are gathering from the plasma and radiation sensors we
simulations; instead, global or coupled models are essential
built can now be used to serve all of our customers.” The
for a complete picture of the environment. “People used to
space environment data is available for applications such
concentrate their efforts on understanding a specific region
as anomaly analysis as well as for scientific studies such as
in space, but it is now clear that we cannot understand the
characterizing Earth’s magnetic cusp.
whole system unless we model the whole system. Everything
Another major space program effort Chen has been
is coupled in various ways, and we’re working toward a much
involved in is work on the U.S. Air Force’s Military Strategic
more collaborative effort among the science community,”
and Tactical Relay System (Milstar). This constellation of
said Chen.
five nuclear-survivable, secure, space-based communicaIn closing, Chen said, “The space environment is extions satellites has been collecting data for nearly twenty
tremely variable. We must continue to develop our underyears, now comprising a large and valuable database. Chen
standing of the basic science of what is happening because
has conducted statistical analysis of upsets for this program.
there is still so much that is unknown. We are in a much
This includes examining whether the space environment at
better position to serve our customers’ spacecraft developgeosynchronous Earth orbit (GEO) during those upsets is
ment efforts when we understand and can share with them
consistent with statistical distributions of past observations.
what they will face in space.”
“The historical references are used to make comparisons
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Technology and Innovation:
The Key to New
System Development
By Sherrie L. Zacharius
E
very new national security space system has its origin
in some simple insight or concept. For example, the
Global Positioning System (GPS) is based on the
principle that radio waves travel at the speed of light. Hence,
the time it takes for a radio signal to travel from a satellite to
a user can be multiplied by the speed of light to determine
the distance between the two. This, together with principles
from geometry, enables a user’s location to be determined
by receiving radio signals from a sufficient number of GPS
satellites.
Another example is that most satellite-based communications exploit the insight that a satellite placed in precisely the
correct orbit above the equator is geostationary. This greatly
simplifies the use of ground antennas, since they can be
installed to point at a single, apparently fixed, location.
These types of insights could not have been realized into
actual space systems without an investment in the technology and innovation to back them up. For example, GPS would
not exist without advances made in spaceborne atomic clock
technology, and without the implementation of an innovative code division multiple access scheme that allows all satellites to broadcast on the same frequency. These fundamental breakthroughs are in turn based on hundreds of others,
including innovative new technologies to detect and mitigate
design and production errors in satellites as they are built.
National security space is now entering a new phase,
where affordable space solutions and the need for resilience
in an increasingly contested and congested environment
have become paramount. This raises the level of challenge
that new system concepts must face, whether the “new
system” is an actual fresh start, a revectoring of an existing
system, or an initiative to extract new capabilities from the
synergistic interplay of current systems. To face this challenge, a culture of innovation must be established at every
level of the acquisition process–from early mission concepts
to design, implementation, and deployment.
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Understanding the Science
Science and technology play a key role in innovation. For
example, scientists continue to develop their understanding
of the environment in which space systems operate based on
dramatic improvements in and greater deployment of scientific instruments. This helps in the understanding of potential space mission constraints and assists in decision-making
about mission design. Likewise, gaining insight into the
capabilities of emerging materials, such as carbon nanotubes,
and how their properties act in the space environment—
which can be significantly different from how they act in
the terrestrial environment—may lead to space systems of
considerable weight and cost savings.
To ensure a deep understanding of the key science-based
issues facing national security space, The Aerospace Corporation
maintains an aggressive program of use-inspired research.
This means that Aerospace researchers press the boundaries
of what is known and actively participate in the scientific
community—publishing in refereed journals, par-ticipating
in national and international forums, and collaborating with
national laboratories and universities.
Having expertise in the science underlying new and
emerging technologies enables Aerospace to help find
answers to questions that have yet to be asked. New developments in remote sensing, for example, may enable climatemonitoring missions not previously conceived, or might find
application in a new technique for nondestructive investigation of suspect parts in a rocket engine. Similarly, developing
insights into the consumption of metallic rubidium by the
glass walls of the lamp within a spaceborne atomic frequency
standard may enable a more effective implementation of
several space payloads.
Focus on the Underlying Issue
In today’s cost-constrained environment it becomes essential to revisit the underlying requirements of a given space
system. This is particularly true when looking at follow-on
systems. If the requirements and constraints go unchanged,
the solution is unlikely to be different. However, in an
environment of rapidly changing threats, one can ask, “Are
these still the right requirements?” Many times, the choices
on how to proceed were derived from the original system
requirements, and to find a truly innovative solution, it is
necessary to identify the real underlying issue. In a rapidly
changing world, the current issue may not be the one that
was envisioned when the original system was conceived.
Aerospace is embarking on a program of internal special
studies to evaluate new and emerging technologies in all
areas—from breakthroughs in fundamental physics to the
application of novel business models. These studies help
Aerospace’s leadership and customers as they address the
issues associated with developing new solutions in a challenging era.
Aerospace also seeks to foster innovation at every level—
questioning assumptions, finding unmet needs, exploiting
new technologies, and developing new approaches within
existing ones. For example, by exploring what can be done
with very small satellites, Aerospace researchers have approached the miniaturization of space from a new perspective. Instead of asking how to shrink a large satellite mission
into a smaller mass and volume, they start with a very small
“CubeSat” class satellite design, then explore how much
larger the small satellite needs to become to accommodate
the full mission. In these cases, along the way, Aerospace
helps energize the small satellite industry base for its customers by licensing its technical approaches to small satellite
subsystems.
Collaborate for Success
A technology-focused culture of innovation is essential for
the national security space enterprise to succeed. Aerospace
seeks to provide a leadership role in this arena but cannot go
it alone. Thus, Aerospace is working to collaborate with partners at all levels—from government customers to national
laboratories to prime contractors and small businesses to
universities. This enables the enterprise to address large efforts, such as the search for solutions for the next generation
of protected communications, in greater depth and fidelity
than any one partner might bring to the effort.
The environment for national security space is rapidly
changing, presenting a challenge to the nation in general
and to Aerospace in particular. One thing is certain: just
as the next war is never like the last one, the challenges of
the future will not be like those of the past. Innovation and
technology will play a vital and important role in achieving
long-term mission success, helping to ensure a responsive
and resilient national security space effort.
The Aerospace Propulsion Research Facility
The newly constructed Propulsion Research Facility (PRF) on The
Aerospace Corporation’s El Segundo, California, campus will
enhance the ability of Aerospace to safely carry out empirical
investigations of energetic systems used by national security space
customers in launch vehicles and satellite propulsion systems.
The PRF brings to fruition a collaborative effort begun more than
a decade ago between Aerospace's Physical Sciences Laboratories
and the Vehicle Systems Division. The PRF is under construction
with expected completion in the fall of 2014.
The 1200-square-foot building is located in the south parking
lot area and will contain three primary laboratories: a chemicals
handling and preparations wet lab; a laser diagnostics room; and
a heavily reinforced main lab for carrying out controlled detonations of pyrotechnic devices, and hot-fire testing of rocket motors
and their components.
Propulsion systems still account for the majority of launch vehicle
failures, despite their long history of use and extensive industrial
experience using them. Propulsion systems feature complex structures characterized by high-energy densities and large thermal
gradients. Materials are often exposed to extreme environments
with narrow margins for maintaining structural integrity. Consequently, small material defects and deviations in nominal operating conditions can quickly lead to spectacular failures, making
anomaly investigation and resolution paramount. The availability
of a testing facility at Aerospace for the characterization of materials and systems under these extreme conditions is critical for the
timely resolution of launch anomalies and failures, and for the
mission assurance required by the corporation’s customers.
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The increasing popularity and functionality of small satellites has helped them move beyond
technology demonstration and into the realm of commercial and governmental applications.
Charles L. Gustafson and Siegfried W. Janson
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CROSSLINK FALL 2014
I
n November 2013, a single Minotaur rocket carried 29
satellites into orbit, setting a new record for the most
satellites deployed in a single launch. Less than two days
later, a single Dnepr beat that record, lifting 32 satellites
into orbit. Such launch rates—inconceivable just a few years
ago—are rendered all the more remarkable considering that
many of these satellites were not sponsored by well-funded
government agencies but by universities and small private
entities.
Evidently, the space industry is starting to realize the
potential of small satellites. Indeed, the last decade has seen
a substantial boom in their development, both domestically
and internationally. Much of this growth can be attributed to
the popularity of CubeSats, a well-known subclass of small
satellites. However, CubeSats are only part of this rapidly
expanding picture. Furthermore, it appears that small satellites are starting to move beyond the demonstration phase to
provide the performance and reliability needed for commercial ventures and governmental applications.
The CubeSat Revolution
CubeSats derive their name from the so-called “1U” building block, which is a 10 × 10 × 10 centimeter cube, typically
weighing around 1 kilogram. Larger CubeSats are built by
stacking these units. Bob Twiggs (then at Stanford University) developed the initial concept in early 1999 after working
with The Aerospace Corporation on his Orbiting Picosatellite Automated Launcher (OPAL) microsatellite. Jordi
Puig-Suari from Cal Poly San Luis Obispo helped refine the
concept and create the specifications.
The first CubeSat launched in June 2003; by the end of
2013, 155 had been placed in orbit, with 78 launched in 2013
alone. The United States, Russia, China, India, Japan, and the
European Union all launched CubeSats in 2013. Almost 20
percent of the CubeSats launched that year were sponsored
by the DOD. Aerospace has built and flown eight CubeSats
since 2004 and is working on seven more.
CubeSats were originally conceived for education and
flight tests of new technologies, but mission applications
such as tactical communications, space weather measurement, and Earth observation are rapidly coming on line. The
ability to design, build, test, fly, and redesign a spacecraft
within one year is an obvious benefit for university students; but such fast development cycles also serve to spur
the evolution of technologies and components for a wide
range of future missions. These technologies can be applied
to larger spacecraft to bring down launch and development
costs. While the current launch architecture may not readily support the easy and timely launch of microsatellites in
general, it does support the easy integration and launch of
CubeSats. Standardization of the spacecraft and its deployment system has provided multiple CubeSat launch opportunities each year with minimal risk to primary missions. Most
are launched using a standardized ejection tube known as
Design Study 1: Microwave Weather Satellite
Mission:
Collect microwave weather measurements (ocean wind vectors,
precipitable weather, cloud water, sea ice)
Design Specifications:
Spacecraft size: 100 × 100 × 140 centimeters³
Design life: 3 years
Orbit: LEO sun-synchronous (6 a.m.)
Altitude: 450 kilometers circular
Inclination: 97.2 degrees
Period: 93.6 minutes
Payload mass/power: 70 kilograms/50 watts
Spacecraft mass/power: 269 kilograms/263 watts
Stabilization: 3-axis
Pointing accuracy: 0.1 degrees
Pointing knowledge: 0.05 degrees
Hardware redundancy: Single string
Radiation environment: Natural
Payload mass and power growth: 25 percent, given that the
payload is still in development
Spacecraft bus mass and power growth: 25 percent
Spacecraft disposal: Reentry within 25 years
Key Assumptions:
Spacecraft designs are unique and not based on any commercial
or existing spacecraft designs
Other Considerations:
Launch: Minotaur 1
Mass exceeds ESPA Rideshare
Volume exceeds ESPA Grande
Refresh requirements variable with number of microsats
CROSSLINK FALL 2014
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ers. These will be large enough to deploy individual microsatellites, potentially increasing the number and frequency of
microsatellite launches in the future.
Recently, Twiggs (now at Morehead State University in
Kentucky) introduced a new class of CubeSats known as
PocketQubs. Measuring 5 × 5 × 5 centimeters, they can be
bundled in groups of eight for deployment from a conventional P-POD or ejected individually by a Morehead Roma
Femtosatellite Orbital Deployer (MR FOD). Four PocketQubs were ejected in November 2013. A “1P” PocketQub
called Wren was crowd-funded and built by the fourmember German startup company StaDoko. Wren contains
a camera, magnetic field sensors, three orthogonal reaction
wheels, and four pulsed plasma thrusters for attitude and
orbit control. At less than 200 grams, it replaced the Aerospace 250 gram, 2.5 × 7.5 × 10 centimeter OPAL Picosatellites, ejected into orbit in January 2000, as the smallest active
satellite ever flown. That record was soon broken when
another CubeSat in the same launch released Peru’s PocketPUCP femtosatellite, which measures only 1.55 × 4.95 × 8.35
centimeters and weighs just 97 grams.
Commercial Applications for Small Satellites
The CubeSat program has enabled Aerospace to design, build, and flighttest a number of satellite components. Shown here is the second-generation
Earth nadir sensor, which achieves a pointing accuracy of 1 degree.
the Poly Picosatellite Orbital Deployer (P-POD), which can
hold up to three units. These P-PODS fly on many international launch vehicles. A 1U CubeSat costs anywhere from
$80,000 to $140,000 to launch—a bargain for government
agencies, research centers, private companies, universities,
high schools, and even individuals. For larger components,
subsystems, or systems, 6U launch tubes are now available,
and standards are being developed for 12U and 27U deploy-
Image of an almost completely frozen Lake Superior taken by AeroCube-4, a 1U
CubeSat.
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Can microsatellites and smaller spacecraft really perform
meaningful tasks? Many in the commercial sector believe
they can. Several companies are marketing optical and
near-infrared imagery as well as full-frame video collected
by small satellites. In November 2013, Skybox Imaging
launched its first satellite and began offering submeter resolution for visible-wavelength imagery and 30 hertz optical
video at slightly lower resolution. The satellites have a mass
of approximately 100 kilograms, with a central core less than
a meter long.
Planet Labs launched four 3U CubeSats during 2013 to
serve as demonstrators for the much larger Flock-1 constellation to provide regular refreshes of imagery anywhere on
Earth. The satellites can achieve a ground sample distance of
approximately 5 meters (assuming a 500-kilometer circular
orbit) with an evident aperture of less than 10 centimeters.
In January 2014, Planet Labs sent 28 additional spacecraft to
the International Space Station and deployed all of them by
March to generate the world’s largest constellation of Earth
imaging satellites. The company has announced plans to
launch an additional 100 CubeSats by April 2015.
Another commercial application for small satellites is
communications. In low Earth orbit (LEO), such satellites
can provide a variety of services, including messaging, e-mail,
and localization, and services to mobile users. Unlike large
geostationary communications satellites with high-gain antennas and high data rates, small satellites in LEO (or “little LEO”
constellations) specialize in low-to-medium data rates using
low-gain, low-power terrestrial transceivers.
In the 1990s, ORBCOMM launched 35 small satellites to
provide commercial machine-to-machine messaging in the
MicroSats
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NanoSats
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PicoSats
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The launch rate for small satellites has increased in the last 20 years, driven by
significant increases in the number of picosats and nanosats launched. All 1U
CubeSats are counted as picosats, and all larger CubeSats are nanosats. The
137–150 megahertz VHF band, with a 4.8 kilobits per second downlink and a 2.4 kilobits per second uplink. The satellites weighed about 42 kilograms each and were launched
on Pegasus and Taurus vehicles into 775-kilometer circular
orbits; 25 are operational today. In 2008, ORBCOMM
launched a set of six replacement satellites, each weighing 80
kilograms. These all failed due to a power system anomaly,
but a new generation of 18 satellites is in production, with
launches planned on the Falcon 9 vehicle. These satellites
will weigh 142 kilograms and will include support for the
Automatic Identification System, which is used to track
ocean vessels.
Government Applications
Spurred in part by successful commercial developments, the
U.S. government has also started examining applications for
small satellites. In 2013, the Air Force Scientific Advisory
Board completed a study for Air Force Space Command
(Aerospace is a member of the board). The study found that
microsatellites “have significant near-term (2–5 years) mission capability.” In particular, the study concluded that:
Microsats can address all Category A weather requirements; microsats can address some critical space situational
awareness (SSA) requirements; other potential near- and midterm microsat missions exist in space-to-surface intelligence,
surveillance, and reconnaissance (ISR) and position, navigation, and timing (PNT); and potential far-term microsat
missions exist in missile warning, PNT, and communications.
In addition, the study found that:
Microsats are not currently well supported by Air Force
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vast majority of nanosats are 1.5 through 3U CubeSats, and the vast majority
of picosats are 1U CubeSats.
launch architecture; microsat ground system costs could prevent effective mission application; and more suitable ground
command and control (C2) architectures and processes exist.
Thus, small satellites can satisfy specific sets of requirements within certain missions—and the number of applications could increase in the future. It is important to note,
though, that small satellites are definitely not suitable for
many Air Force missions and requirements—for example,
protected and nuclear-survivable communications. Small
satellites are inherently less capable than large satellites in
satisfying requirements for high-power-aperture products.
Small satellites are not now, nor will they ever be, a panacea
for Air Force Space Command.
It is also important to note that in cases where small
satellites do have application, they will require different
launch and ground systems than those used for large satellites.
Without approaches that better suit small satellites, it may not
be possible to effectively use them for Air Force missions.
The findings of the Scientific Advisory Board were supported by proof-of-concept engineering designs created
at Aerospace. Two of these designs focused on microwave
imaging and space-based surveillance.
The microwave imaging satellite was designed for
weather monitoring using a specific payload currently
in development. It featured three-axis stabilization and a
pointing accuracy of 0.1 degree. Design life was three years.
Measuring 100 × 100 × 140 centimeters and weighing 269
kilograms, it exceeded the size limits for the EELV Secondary Payload Adapter (ESPA), and would require a dedicated
launch on a small vehicle (such as a Minotaur 1).
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Design Study 2: LEO to GEO Tracker Satellite
GeOST in low altitude, zero inclination, circular orbit
pointing angle
Mission:
Observe GEO targets with a LEO microsat
Design Specifications:
Spacecraft size: 60 × 60 × 60 centimeters³
Design life: 3 years
Orbit: LEO
Altitude: 700 kilometers circular
Payload mass/power: 29 kilograms/26 watts
Spacecraft mass/power: 119 kilograms/106 watts
Key Assumptions:
Limiting technology is pointing accuracy
Two or more microsats in a circular LEO orbit
Other Considerations:
Technology readiness level: 3/5 system/components
GEO object detection and tracking from sub-GEO and
super-GEO are plausible
The surveillance satellite was designed to detect and track
geostationary objects—a function currently provided by the
Space-Based Space Surveillance system (SBSS). The design
clearly showed the feasibility of using a microsat to host an
optical payload capable of sensing small objects in geosynchronous orbit from LEO. Compared with the current SBSS
mission profile, this approach would achieve substantially
lower complexity and lifecycle cost. Moreover, the revisit
rate could be gradually increased through incremental addition of capability, with a relatively manageable funding
profile. The same capability could be used for high LEO and
medium Earth orbits, if needed, providing a consistent approach to object detection and tracking. Overall, the panel
concluded that this is a high-payoff area for microsat use.
CubeSats in Action
Typical CubeSat missions in 2013 included flight-testing new
technologies, hands-on education, store-and-forward communications, space science measurements, and Earth observation. Aerospace is helping the U.S. government develop
several new mission areas. Some examples of government10 CROSSLINK FALL 2014
sponsored Cubesats launched in 2013 include:
• AeroCube-5A and -5B. These 1.5U CubeSats were designed, built, and tested at Aerospace. They will demonstrate improved pointing capabilities needed for future
missions and flight-test the CubeSat Terminator Tape
Deorbit Module from Tethers Unlimited.
• SENSE-A and -B. These 3U CubeSats were sponsored
by the Air Force Space and Missile Systems Center/Development Planning Directorate (SMC/XR) and built by
Boeing. They will demonstrate collection of space weather
data and timely integration of that data into ground-based
ionospheric models for improved predictions.
• SMDC-ONE-2.3 and -2.4. Eight of these 3U CubeSats
were developed by Miltec for the U.S. Army Space and
Missile Defense Command to receive and forward data
from unattended ground sensors and to provide voice and
text message relay for field units.
• ORSES. This 3U CubeSat was developed by the Operationally Responsive Space office and the U.S. Army Space
and Missile Defense Command to provide communications and data capabilities for underserved tactical users.
• STARE-B. This 3U CubeSat was developed by Lawrence
Livermore National Laboratory to test the Space-based
Telescopes for Actionable Refinement of Ephemeris
(STARE) concept. STARE, in conjunction with groundbased assets, could provide improved accuracies for the
orbital elements of space debris. Better orbital ephemerides should produce fewer false alarms during collision
prediction routines, resulting in fewer collision-avoidance
maneuvers for all LEO spacecraft.
Because there are multiple launch opportunities each
year, it is now possible to design, build, fly, and analyze
flight data within a year. This is 5 to 7 times faster than the
traditional development cycle, thus accelerating the evolution of new technologies for small satellites—e.g., solar cells,
microprocessors, field-programmable gate arrays, attitude
sensors, GPS receivers, etc. For example, Aerospace has
developed triaxial reaction wheels and Earth nadir sensors
that fit within a 1-cubic-inch volume, and a GPS receiver
that occupies about 2 square inches of circuit board space.
These subsystems were on at least two previous spacecraft,
and the development team is now on its third cycle of modifications, based on flight performance, to improve accuracy
and reliability. The second-generation Earth nadir sensor has
1-degree pointing accuracy.
For the NASA-sponsored Optical Communications and
Sensor Demonstration (OCSD) mission, which will fly in
2015, Aerospace is developing a star tracker with less than
2-cubic-inch volume to provide pointing knowledge better
than 0.05 degree; an approximately 10-cubic-inch, 5-to200–megabits per second laser transmitter; and a 6-cubicinch warm-gas propulsion system. The laser transmitter will
enable unprecedented communication rates for a CubeSat. A
terabyte of memory—in the form of eight or more 128-giga-
panies, FFRDCs, and various NASA centers. Aerospace has
embarked on a NASA-funded effort to develop an advanced
hybrid-rocket motor propulsion unit for CubeSats in collaboration with Pennsylvania State University. Other NASAsponsored CubeSat propulsion efforts include development
of a hydrazine propulsion module, a radio-frequency ion
engine that uses iodine as propellant, a “green” (nontoxic)
propulsion module, and an electromagnetic plasma thruster.
60
50
40
30
20
10
Summary
2009
2005
2001
1997
1993
1989
1985
1981
1977
1973
1969
1965
1961
1957
0
The number of nations and government consortia active in space has steadily
increased over the last 50 years.
bit Flash memory cards—can literally be held in the palm of
the hand. Unfortunately, it would take more than a hundred
years to download a terabyte of data using a typical small
satellite radio frequency downlink (at about 100 kilobits per
second) from LEO using a single ground station. The laser
downlink will demonstrate a new communications channel
with a 2 to 3 order of magnitude increase in data rate for
CubeSats and other small satellites.
The OCSD mission is one of four CubeSat flight programs supported by NASA’s Small Spacecraft Technology
Program. The other three are: the Edison Demonstration
of Small Satellite Networks, a free-flying cluster of eight
CubeSats that will take space radiation measurements and
crosslink information between spacecraft; the Integrated
Solar Array and Reflectarray, a Ka-band antenna integrated
into a solar array for up to 100 megabits per second data
rates to a ground station; and the CubeSat Proximity Operations Demonstration, a rendezvous and docking mission
using two 3U CubeSats.
NASA’s first CubeSat, GeneSat-1, reached orbit in
December 2006 to conduct space biology experiments.
Subsequent space biology CubeSats flown by NASA include
PharmaSat (2009) and the Organism/Organic Exposure
to Orbital Stresses spacecraft (2010). Also in 2010, NASA
built and flew a solar-sail experiment, NanoSail-D2, which
packed a 10-square-meter sail into a 3U CubeSat (which is
only 30 centimeters long).
In 2012, NASA announced the In-Space Validation of
Earth Science Technologies (InVEST) program, targeted specifically at CubeSats. Four out of 23 submitted projects were
selected. The winners were MIT Lincoln Laboratory, the Johns
Hopkins University Applied Physics Laboratory, the University of Maryland, and The Aerospace Corporation, which
proposed “A CubeSat Flight Demonstration of a PhotonCounting Infrared Detector.” The 3U CubeSat, containing a
cryocooled, state-of-the-art photon-counting detector array,
will fly in 2016.
NASA is also funding a wide range of technologies for
small satellites and CubeSats at universities, private com-
The U.S. space program started with the launch of Explorer-1, a 14-kilogram microsatellite, followed by Vanguard-1,
a 1.7-kilogram nanosatellite. More than five decades of technological advancements have packed greater functionality
into microsatellites and smaller spacecraft. This has driven
down cost per unit and expanded the deployment of new
spacecraft by many countries, corporations, organizations,
and even individuals. CubeSats are one example of a “new”
spacecraft that has radically changed the small satellite field.
Basic laws of physics place limits on phenomena such as
ground resolution and antenna gain for a given aperture diameter, so small satellites cannot be used for many demanding military applications. On the other hand, small satellites
are relatively inexpensive and can be distributed in constellations to provide simultaneous measurements, or reduced
revisit times, with reduced spatial resolution. The microwave
imager sounder and GEO satellite tracker that Aerospace
studied demonstrate the feasibility of this approach. Commercially, microsatellites have already been used to provide
LEO data communications, and further improvements in
data rate and availability are possible. Thanks to its early
involvement in this field, Aerospace is well positioned to
help the U.S. government take advantage of the intriguing
possibilities.
Further Reading
The Aerospace Corporation, “Photos from Space,” http://
www.aerospace.org/2014/01/30/photos-from-space//
W. Graham, “Russian Dnepr Conducts Record Breaking 32
Satellite Haul,” NASASpaceFlight.com (Nov. 21, 2013).
Q. Hardy and N. Bilton, “Start-Ups Aim to Conquer Space
Market,” New York Times (March 17, 2014).
H. Helvajian and S. Janson, Small Satellites: Past, Present, and
Future (The Aerospace Press/AIAA, El Segundo, CA, 2008).
S. W. Janson and R. P. Welle, “The NASA Optical Communication and Sensor Demonstration Program,” SSC13-II-1,
27th Annual AIAA/USU Conference on Small Satellites
(Logan, UT, August 12-15, 2013).
CROSSLINK FALL 2014 11
Internal Research and
Development Spurs
Advancements and
Fills Technology Gaps
Aerospace internal research has led to real-world components
that vastly miniaturize space environment sensors.
T. Paul O’Brien
12 CROSSLINK FALL 2014
T
he environments of near-Earth space and
the upper atmosphere pose unique challenges for designing and operating satellite
systems. For example, radiation can disrupt critical electronic systems in satellites. Understanding such phenomena is important for designing
and operating space systems. The Aerospace
Corporation has cultivated the capability to
design, develop, and produce such instruments
and technologies, which have helped numerous
space missions succeed.
However, the instruments and technologies
needed to measure the space environment have
often been weighed down by unnecessarily large
custom electronics. Recognizing this challenge,
Aerospace has made a significant investment
during the past several years in miniaturizing
the electronics required by space environment
sensors.
Microdosimeter data, incorporated into the Spacecraft Environmental Anomalies Expert System
Promising work has been done in the field of
(SEAES), supports space situational analysis and anomaly resolution for satellites in low Earth orbit.
Here, near-real-time data from the microdosimeter payload is fed into a SEAES demonstration on a
application-specific integrated circuits (ASICs)
classified system. The data is mapped from the Rapid Pathfinder to other low Earth orbit vehicles.
for space environment sensors. An ASIC is a
SEAES then produces hazard maps. This map shows the radiation dose behind thinly shielded components both along the Rapid Pathfinder ground track and in contours. The red regions indicate locaset of miniaturized electronic circuits that is
tions of elevated risk of anomalies caused by single-event effects, internal charging, and total dose.
customized for a particular use rather than a
more typical assembly of discrete general-use
anomalies caused by space weather. As a part of this project,
components.
the initiative funded the development of a visualization caBecause of their reduced mass, power, and size compared
pability for Aerospace’s Spacecraft Environmental Anomalies
to discrete components, ASICs can offer greater capability
Expert System, Real-Time (SEAES-RT).
in instruments on satellite systems. ASICs have dramatically
SEAES-RT was developed for the Rapid Attack Identialtered the design of space environment sensors and enabled
fication and Detection Reporting System (RAIDRS). This
vast improvements in their capabilities despite fixed resourcground-based system detects and classifies instances of radioes and other limitations.
frequency interference to satellites and their ground elements.
Scientists and engineers in Aerospace’s Space Science
The original SEAES was an interactive system that was used
Applications Laboratory began work on ASIC applications
after space weather anomalies occurred. SEAES-RT autoin space environment sensors as an independent research
matically assembled data from sensors on the ground and in
and development program in 2002 (“Mixed-Signal ASIC
geostationary orbit to provide space situational awareness in
Design for Microsat and Smallsat Applications”). This effort
the widely used red-yellow-green stoplight format.
capitalized on decades of experience in designing, building,
To address concerns that the data sources for SEAES
and launching spaceflight instruments to measure the space
were insufficient, the Space Weather Initiative investigated
radiation and plasma environments.
the possibility of dedicated satellite constellations for moniThe goal was to reimplement those common functions
toring space weather. One of the initiative’s key insights was
in a physically compact, low-resource, easily manufactured
that some hazards were so localized, even a dense constelchip. The first application chosen for development was the
lation of monitoring satellites could not adequately define
microdosimeter, based on its relevance to and suitability for
them. Instead, an environmental sensor was needed on every
all satellites, especially small ones. A dosimeter measures
satellite. The microdosimeter was the first step toward that
radiation dose, which is the deposit of energy through iongoal: a sensor so small and simple that it was a component,
ization and mechanical or chemical reactions.
not a payload.
Simultaneous Development Efforts
At the same time the ASIC development effort started,
Aerospace began a larger internal research effort, the Space
Weather Initiative, which included a project to develop space
situational awareness tools for anticipating and diagnosing
Microdosimeter Development
Aerospace scientists successfully developed a microdosimeter about the size of a postage stamp with the insight and
guidance learned from the Space Weather Initiative, along
Crowd-Sourcing Space Radiation Hazard Monitoring
Crowd-sourcing weather data has a long history and is still in use
at sea, in the air, and on land. The arrival of microdosimeter technology may lead to crowd-sourced weather in space as well.
resolve radiation environment structures that a satellite traverses
in seconds, while RadFETs can typically only observe changes from
one orbit to the next, or even one day to the next.
Mariners record sea surface and weather conditions and share
this information with organizations like the National Oceanic
and Atmospheric Association (NOAA) for use in operational and
climatological weather and marine products. These products allow
other ships to navigate and operate more successfully.
Equipped with microdosimeters or similarly accurate, targeted
sensors, satellites could routinely report their conditions back to a
central authority through ground-based communication networks,
in direct analogy to VOS or CoCoRaHS. Satellites move quickly
through different radiation regions, so their reports would need to
have fairly high-time resolution (seconds to minutes, depending on
the orbital period). For maximum utility, the reports would need to
have low latency (minutes); although, for anomaly resolution, data
with latencies up to a day or two can still be very useful.
The World Meteorological Organization’s Voluntary Observing
Ships (VOS) program employs lightly trained volunteers operating
government-supplied equipment aboard thousands of vessels.
Prior to the age of satellite weather observations, the VOS scheme
was the only way to cover the vast oceans. Today’s offshore
weather is tomorrow’s onshore weather. In the satellite age, the
VOS system remains a vital part of monitoring the ocean surface
and offshore weather.
Following the model of mariners, aircraft pass along weather observations, especially clear air turbulence, to air safety controllers.
Because turbulence is difficult to detect remotely, the air safety
system relies on routine reports from pilots flying through rough
air. Relayed through the air traffic control system, turbulence
reports lead to warnings from the cockpit for passengers to take
their seats and fasten their seat belts. In those rare cases when
severe turbulence is encountered without warning, it is common
for passengers and flight crew to receive serious injuries. Thus,
crowd sourcing of atmospheric conditions probably prevents serious injuries every day.
The advent of the Internet has dramatically reduced barriers
to forming a crowd-sourced weather observation network. For
example, today the Community Collaborative Rain, Hail, and
Snow Network (CoCoRaHS) provides a coordinating umbrella for
thousands of volunteer precipitation observers around the United
States. These volunteers make daily standardized measurements
using equipment often purchased themselves. The shared data offers a wide variety of users a supplement to the more capable–but
also more expensive–national weather station network.
The methods and value of crowd-sourcing has an obvious
analogue in space weather. Social media applications have been
developed to catalogue and map observations of the aurora.
However, as yet, satellite operations have not been able to take
advantage of crowd-sourcing. All of the examples here required
a low-cost means of observing the relevant weather conditions–
special equipment or the five senses of humans on the scene.
This is why the microdosimeter is a potential game changer: it
weighs only 20 grams; interfaces to common, existing electrical
and housekeeping data infrastructure found on most satellites;
and can measure radiation dosage as small as 14 microrads.
Radiation-sensing field effect transistors (RadFETs), which employ
an older technology in the same size scale as the microdosimeter, are orders of magnitude less sensitive–microdosimeters can
VOS and CoCoRaHS, in contrast, typically have lower time resolution and higher latency; therefore communications infrastructure
will play an important role in realizing a crowd-sourced, spacebased radiation observation network. Once the data from distributed sensors are assembled, however, data-assimilative models
could ingest dosage and location data to fill in the global environment on a high-resolution grid and estimate upcoming conditions
along the specific track of any vehicle.
More latent data could be used to accurately reconstruct the
global environment for anomaly resolution. In either timeframe,
the crowd-sourced network would support vehicles with and
without their own environmental sensors. An ad hoc distributed
approach would be especially helpful in low-altitude, mediumaltitude, and highly elliptical orbits, all of which cross through
different regions of the radiation belt, and are, therefore, sensitive
to more details of the radiation belt structure and dynamics than a
geostationary platform. The first critical technology along this path
is the microdosimeter developed at The Aerospace Corporation.
Looking farther ahead, the biggest hole that would be left by a
crowd-sourced network of dosimeters is the spacecraft surface
charging hazard posed by hot electron plasmas. These plasmas
are too low in energy to penetrate the surface of the spacecraft
(or the dosimeter), but the charging they cause can lead to
electrostatic discharge, which can destroy strings of solar cells,
issue phantom commands, create short circuits, or simply burn
spacecraft components and materials.
The same Aerospace team that developed the microdosimeter is
developing a charge deposit sensor to characterize the surface
charging hazard. The plasma that causes this charging is known to
be sufficiently variable in time and space. The consensus is to fly
one or more surface charging monitors on every vehicle. Whether
that solution is ever realized, the crowd-sourcing infrastructure
is the same as what would be needed for radiation dosimetry. In
fact, it may turn out that with a sufficiently dense crowd-sourced
network of ad hoc surface charging sensors, some orbit regimes,
such as geostationary orbit, may not need a surface charging sensor on every vehicle, just on a lot of them. Aerospace looks to the
future as it continues to develop these enabling technologies.
Other ASIC Applications
After the success of the targeted sensors, Aerospace researchers turned their attention to developing ASICs for more
sophisticated sensors that performed such common tasks
as fast coincidence logic and pulse-height analysis. Fast
coincidence logic measures the nearly simultaneous energy
deposits in multiple detector elements as a single particle
passes through them. Pulse-height analysis examines the size
of the electronic pulses generated by these energy deposits.
10.9 inches
Courtesy of Millennium Space Systems
The microdosimeter payload on the Rapid Pathfinder in low Earth orbit.
The hardware was designed by Aerospace to support technology demonstration
and vehicle anomaly resolution.
Courtesy of Teledyne Microelectronics
with a sequence of continuing independent research and
development projects. The microdosimeter weighed only 20
grams and consumed as little as 144 milliwatts. More important, it was powered by a range of common bus voltages and
could have up to four outputs, each of which was the same
electrically as a common thermistor output.
In 2006, Aerospace filed a patent application for its microdosimeter. Once a patent was issued, Aerospace licensed the
technology to Teledyne Microelectronic Technologies for
manufacture and sale.
The microdosimeters can be launched on almost any satellite needing space situational awareness. They are currently
implemented in spacecraft at low Earth orbit, geostationary transfer orbit, and even lunar orbit. These components
provide valuable data for space situational awareness, space
weather anomaly resolution, and verification of satellite design models. In fact, the microdosimeter’s compactness and
high precision have opened up other opportunities in ground
and atmospheric radiation dosimetry, such as monitoring
crew radiation dose on transpolar or high-altitude flights.
While comprehensive, highly capable space environment
sensors will always be needed, the microdosimeter has established a new niche: compact, targeted sensors that measure
the effects of the space environment, rather than the particles
that cause those effects. Aerospace followed up on the microdosimeter with a charge-deposit sensor, which measures surface charging on a spacecraft, and an electrostatic discharge
recorder, which counts and digitizes high-frequency electrical transients indicative of electrostatic discharge, the likely
cause of many satellite anomalies.
The microdosimeter became commercially available in 2010. Aerospace
has licensed the technology to Teledyne Microelectronics for production.
Such sensors were needed on several NASA programs, including the Van Allen Probes, the Magnetospheric Multiscale
mission, and the VISIONS (Visualizing Ion Outflow via Neutral Atom Imaging During a Substorm) sounding rocket. For
these programs, Aerospace designed new ASICs to perform
these common tasks and gave them colorful names such as
MAPPER, DAPPER, and MRA. These new ASICs enable
more capabilities within the same limited volume that used
to be occupied by analog and digital signal processing circuit
boards. For example, a single MAPPER chip can replace up
to 12 boards of discrete analog electronics.
Because of the modularization and the reduced volume,
mass, and power in ASICs, Aerospace researchers have been
able to solve tough challenges in developing space environment sensors. For example, the fast coincidence logic and
pulse-height analysis ASICs are implemented in the magnetic
electron ion spectrometer (MagEIS) that Aerospace developed for NASA’s Van Allen Probes.
MagEIS uses coincidence to reduce out-of-view background by rejecting particles that do not strike all the
required elements in the sensor. The physical alignment
of these elements limits the trajectory of particles that can
be counted as foreground and rejects all other particles as
background.
The MagEIS pulse height analysis capability allows the
sensor to estimate and remove background from particles
that scatter within or penetrate through the sensor material.
By examining the combination of energy deposits in the various sensor elements, background particles can be identified
for exclusion.
As a result of miniaturization, each of the Van Allen
Probes carries four MagEIS units with different energy or
angular coverage. A previous mission, the Combined Release
and Radiation Effects Satellite, carried only one.
Aerospace Develops Instruments for Van Allen Probes
The Radiation Belt Storm Probes (RBSP) mission
is part of NASA’s “Living With a Star Program,”
designed to explore the fundamental processes that
generate hazardous space weather effects near
Earth. NASA selected the Applied Physics Laboratory
at Johns Hopkins University as the satellite prime
contractor and a team of researchers, scientists, and
engineers from The Aerospace Corporation to provide
the instrument payload for the mission.
Outer radiation belt (electrons)
Named the Van Allen Probes mission in honor of the
work of James Van Allen in discovering and characterizing the space radiation environment, the two
spacecraft designed for this mission were launched
from Cape Canaveral, Florida, on August 30, 2012,
into highly elliptical orbits that cross the inner and
outer Van Allen belts. The probes are gathering data
with the necessary spatial and temporal resolution to
answer long-standing questions about the dynamics
of the natural radiation environment.
Inner radiation belt (protons)
Van Allen probes B
Van Allen probes A
Building on decades of experience in the design and construction of
spaceborne instruments, Aerospace scientists and engineers conceived,
designed, and built two unique instrument packages for the Van Allen
probes mission—the Magnetic Electron Ion Spectrometer (MagEIS) and
the Relativistic Proton Spectrometer (RPS) to measure with unprecedented accuracy the outer and inner Van Allen radiation belts. Outfitted with
the instruments, the Van Allen Probes have now unambiguously detected
the presence of transient regions of increased radiation surrounding
Earth, revealing the existence of important structures and processes
within these hazardous regions of space. Data of this type are essential
for the next version of the AE9/AP9 environment specification models.
Data from the MagEIS instruments have provided the first clear evidence
of a fundamental plasma physics process known as drift resonance,
operating in Earth’s magnetosphere. This is illustrated in the figure to
the right, where azimuthally drifting outer zone electrons (energy approximately 100 kiloelectron volts) resonantly exchange energy with
electromagnetic waves. The interaction occurs when the period of the
electromagnetic oscillation (panels b and c) matches an integer multiple
of the electron drift period. The particle flux oscillations are in phase with
the wave at the resonant energy (approximately 80 kiloelectron volts)
and show the characteristic phase lag at energies above and below this
value (panel a).
In addition to advancing scientific knowledge, Aerospace scientists and
Conclusion
Custom application-specific integrated circuits incorporated in
a magnetic electron ion spectrometer. The spectrometer depends
heavily on these circuits for signal processing and background
removal. The resource savings from this setup allows a spacecraft to
carry four spectrometers, whereas a previous mission from 1990 to
1991 could only carry one.
As of 2011, microdosimeter data from the Rapid Pathfinder
satellite are being sent in near real time to a SEAES demonstration supporting that vehicle and others in low Earth
orbit. This convergence of microdosimeter and SEAES
development partially realizes the vision of ASIC-based sensors providing space situational awareness for all satellites.
While the goal of having a space environment sensor on
every satellite has not been realized, the technical hurdles
have mostly been overcome. ASICs can be found as critical enabling technologies in many targeted and scientific
space environment sensors developed at Aerospace. ASIC
technology is also being implemented in national security,
civil, and commercial space applications. Developing ASIC
technology to reduce the resource requirements for onboard
space environment sensors has been a long-term develop-
32 keV
=2
Residual flux
57 keV
80 keV
RMS amplitude
146 keV
185 keV
221 keV
100
50
0
-50
-100
Phase (deg)
0.4
0.3
0.2
0.1
0
111 keV
50
100
150
Energy (KeV)
200
(b)
2
Br MFA (nT)
The recently released AE9 and AP9 models
output a detailed statistical estimate, but additional radiation measurements are needed for
the models to achieve their full capability, and
give spacecraft designers the accuracy they
need to develop long-lived space assets without unnecessary and costly overdesign. The
results Aerospace gathers from these probes
will allow more rigorous analysis of the risk to
planned missions from radiation hazards, such
as total dose degradation of microelectronics,
internal electrostatic discharge, and background noise in imaging sensors. Preliminary
RPS data have already influenced the system
trades and designs for future national security
space missions.
(a)
22 keV
0
-2
4580
DAWS (nT)
engineers are also using data from the Van
Allen probes to develop new space radiation environment models for satellite design
and mission trade studies. While the AE8 and
AP8 models, which have been the industry
benchmarks for several decades, output an
estimate of the average energetic-particle flux,
they do not provide information on the natural
variability of the environment. Quantifying
the percentiles of the environment will enable
the trade of space hazards mitigation against
other system trades.
(c)
4560
4540
4520
4500
4480
15:45:00
16:00:00
16:15:00
16:30:00
In this figure, azimuthally drifting outer zone electrons (energy approximately 100 kiloelectron volts)
resonantly exchange energy with electromagnetic waves.
– Seth Claudepierre, Ionospheric and Atmospheric Sciences, Space Sciences Department
ment effort that was born from and often sustained by the
Aerospace Technical Investment Program.
Further Reading
Aerospace Report No. ATR-2003(8194)-2, “GPS Observations of the Upper and Deep Atmosphere: (GOUDA)–Phase
A Study” (The Aerospace Corporation, El Segundo, CA,
2003).
Aerospace Report No. ATR-2003(8194)-1, “Space Weather
Instrumented Sentinel System (SWISS-GEO)–Phase A
Study” (The Aerospace Corporation, El Segundo, CA, 2003).
Environmental Anomalies Expert System (SEAES)–IR&D
Developments FY06 to FY09” (The Aerospace Corporation,
El Segundo, CA, 2009).
J. Blake et al., “The Magnetic Electron Ion Spectrometer
(MagEIS) Instruments aboard the Radiation Belt Storm
Probes (RBSP) Spacecraft,” Space Science Review, Vol. 179,
pp. 383–421 (June 2013).
J. Mazur, W. Crain, M. Looper, D. Mabry, et al., “New
Measurements of Total Ionizing Dose in the Lunar Environment,” Space Weather, Vol. 9, No. S07002 (July 2011).
Aerospace Report No. ATR-2008(8073)-2, “On-Board Space
Environment Sensors: Explanations and Recommendations”
(The Aerospace Corporation, El Segundo, CA, 2008).
Aerospace Report No. ATR-2009(8073)-2, “Spacecraft
2025 and Beyond: The Next Generation
of Protected Tactical Communications
Developing affordable, protected, and interoperable satellite
communications systems are goals of tomorrow’s space
and ground architectures.
Jo-Chieh Chuang, Joseph Han, and Bomey Yang
I
n 2011, the U.S. Air Force’s Joint Space Communication
Layer (JSCL) Initial Capabilities Document (ICD) projected
military communication needs for 2025 and beyond. It
envisions Military Satellite Communications (MILSATCOM) capacity in a contested environment will increase
significantly in coming years, and surpass current program
capabilities. Several new MILSATCOM capabilities were
identified, including increasing connectivity, antijamming
protection in a contested environment, data rates higher
than 512 kilobits per second for protected communications
on the move (PCOTM) terminals, increasing of capacity in
concentrated theaters, and significant high data rate and capability to support remotely piloted airborne (RPA) missions
with secure command and control and mission data. The
U.S. government wants to provide significant enhancements
to MILSATCOM capabilities for tactical missions, but at the
same time, needs to reduce overall costs because of budget
reductions.
To meet these challenges, the Air Force SMC/MCX (Advanced Concepts Division) initiated a 90-day MILSATCOM
architecture study in 2011. Aerospace was the technical lead
and a major contributor to the study, including introducing a
disaggregated concept that separates strategic and tactical missions. Aerospace presented more than 80 technical reports to
the MILSATCOM community during 2011–2012. The study
result was well received by the Air Force’s Space and Missile
Systems Center (SMC) leadership and the U.S. Congress.
Based on the results of this study, the Air Force established the “Military Satellite Communications Space
Modernization Initiative Investment Plan,” which led to the
two-year, protected military satellite communications effort
“Design for Affordability Risk Reduction” begun in October
2012. The study and hardware/software demonstrations include the U.S. government-owned (nonproprietary) protected
tactical waveform (PTW), as well as protected tactical service
(PTS) system concept developments. The study also includes
an assessment of the overall space communication architecture, commercial-like mission management subsystem functions, gateway design for network interoperability, information assurance practices, and affordable terminal design.
Aerospace has actively participated in this effort, assisting
the U.S. government in establishing requirements, including multiple scenarios for contractors to conduct analysis
and trade-offs; performing analysis of the protected tactical
waveform; designing government reference architectures for
cost estimates and performance analysis; conducting relevant
systems engineering studies for multiple communication
architectures; and evaluating contractors’ analysis and results.
The Protected Tactical Waveform
The PTW aims to support future protected tactical systems.
The U.S. government initiated its development with Aerospace, other federally funded research and development
centers (FFRDCs), and military terminal program offices
(TPOs) in late 2011. Seventeen contractors contributed to
the development of the PTW under the protected Broad
Agency Announcement (BAA) Phase I contract from October 2012 to July 2013. Since then, the government, FFRDCs,
and TPOs continue to refine the PTW.
The PTW is designed with frequency-hopping spread
spectrum (FHSS) to provide greater antijamming capability, featuring a mix of the current protected waveform and
the commercial waveform. The PTW has several significant
design features, including:
• It will support unclassified terminal development for
forward users in a high-risk environment. For example, it
will support the U.S. Army PCOTM to the Company level
for high-data-rate antijam capacity (at 512 kilobits per
second). This capability addresses new features noted in
the JSCL and will reduce the terminals’ cost, since classified terminal cost is a significant part of the total protected
MILSATCOM cost.
• It will support multiple user groups through table-based
TRANSEC. In this design, if a terminal is compromised,
the impact to the mission is limited to the particular user
group. The other terminals in the affected user group
can be quickly rekeyed because only a subset of the total
terminals would require rekey.
• It supports multiple satellite communication architectures, from simple transponder satellites (commercial or
Wideband Global SATCOM [WGS]) to complicated, fully
processed satellites of the future. These features enable
The protected tactical waveform supports all four of the existing satellite communication architectures: pure transponder, dehop/rehop transponder, partial
processed, and full processed.
enterprise and resilient capability by multiple SATCOM
systems because different antijam capabilities can be
achieved by multiple SATCOM architectures.
• It is capable of frequency-hopping and will have comparable antijam capability for current protected systems
from the waveform point of view. Other antijam performance differences will depend on the space payload
design, frequency-hopping bandwidth, and attenuation
loss of different frequency (Ku, Ka, or EHF).
• It has new functions to support forward (downlink to
users) antijam capability by short interleaver. This new
feature will ensure the robustness of the antijam capability for command and control (C2), while providing high
data rate at up to 137 megabits per second for RPA user
data. This feature addresses JSCL for future RPA applications.
• It supports noncontiguous bandwidth-hopping capability, which can occur between fixed frequency bands
without interfering with existing users on WGS or commercial satellites. This feature allows for greater flexibility of satellite operations.
• It adopts commercial standards Digital Video Broadcasting Satellite Second generation (DVB-S2) and Digital
Video Broadcasting Return Channel via satellite (DVBRCS) with some unclassified military unique waveform
features. Herein is the ability to produce affordable
modems for space and terminal systems by multiple
industry vendors. The modem cost is anticipated to be
lower than current costs because of competition from
multiple vendors.
• PTW antijam modems can replace current wideband,
nonhopping modems, and can provide antijam capability to current wideband terminals or commercial terminals through modem swaps, which is an affordable way
forward in the near term.
• It can be used for future high-capacity, antijam protected
theater tactical satellites or hosted payloads for specific
missions including RPA, manpack terminals for special
forces requiring antijam capabilities, and for low-probability interception (LPI) and low-probability detection
(LPD).
To provide antijam protection against many different
threats, the waveform uses low forward-error correcting
(FEC) code rates along with channel interleaving, which
offers robust communication against partial-band and
partial-time jammers.
The waveform allows for terminals to be operated by
unclassified personnel, as well as enabling forward deployment of PTW terminals. The waveform defines the
controlled messages between terminal modem and terminal end cryptographic unit (ECU), which will allow all of
the classified information to be self-contained within the
terminal ECU during operations.
The waveform uses random frequency and time for secure transmissions of information. A table-based, National
Security Agency (NSA)–certified, transmission security
(TRANSEC) algorithm employed in PTW allows a group
of terminals to share the same table with frequent system
refresh. The separation of multiple PUGs can provide more
security features and keep any impact to the mission to a
minimum. The rekey capability to a small set of terminals
can speed up operations recovery and simplify mission
management.
It is essential for the waveform to support many types
of space system communication platforms ranging from
terminals operating at a disadvantage because of limited
transmission power, or those with low-data-rate needs, to
terminals that demand high-data-rate links. The new waveform, on the return link (uplink) from terminals to space/
hub, uses low-order modulation with low FEC code rates
to support terminals with low-data-rate needs, and highorder modulation with high FEC code rates to support
terminals with high-data-rate demands. The forward links
from space/hub to terminals will be time-shared among
several receiving terminals; therefore, modes with high
throughput have been defined.
Aerospace has performed extensive simulation and
actively participated in the PTW working group, providing significant technical inputs in performance analysis
for robust antijam capability, acquisition and tracking for
terminal log onto the system, dynamic resource allocation
(DRA) for efficient resource usage, and mobility protocols
for seamless beam handover. Aerospace engineers reviewed
83 PTW change proposals from the contractor community,
other FFRDCs, and TPOs; provided feedback to the government; and participated in the voting process. The rigorous PTW change proposal process ensured the waveform
is mature. The contractors, who have already implemented
part of PTW for the space and terminal modems, have now
endorsed it.
The PTW provides return link data rates ranging from
21.6 kilobits per second to 137 megabits per second, supporting a variety of terminal platforms and applications.
Small and disadvantaged terminals such as manpack terminals with limited transmission power can use the low-datarate modes (21.6 kilobits per second) to achieve fair-quality
voice communication with LPI and LPD features. Certain
tactical missions such as RPA require antijam protection at
high-data-rate (137 megabits per second) links to transmit
high-quality image data, which is 17 times higher than that
of current protected systems.
In an effort to broaden future competition and the industrial base for this new waveform, commercial waveform
standards, including DVB, in particular DVB-RCS and
DVB-S2, are used to provide definitions for the communication modes. These standards have been in use by the sat-
Notional Protected Tactical Service Concept
Protected tactical
satellite
Commercial transponder
satellite
AEHF
No crosslinks.
Ground gateway for
interconnectivity
Crosslink
Unclassified waveform
Virtual
payload
Protected
tactical
waveform
terminals
Teleport or
gateway
Virtual
payload
Ground connectivity
Network connectivity
Affordable protected system features:
Global information grid
Backup
mission
planning/
management
Teleport or
gateway
Low-cost
mission
planning/
management
• Supports multiple satellite architectures (transponder, DRT,
partially processed, and fully processed)
• Unclassified waveform (information assurance, suite B crypto)
• Low-cost terminal
• Simpler payload (or processing moved to ground)
• Simpler mission planning and management
• No crosslinks
• Reliable mobile communication
• Comparable antijamming capability
• High-connectivity, user-to-user and user-to–global information grid
A notional protected tactical service concept that supports multiple satellite architectures.
ellite communications industry for more than a decade and
the technology is mature. The performance characteristics
of the modulation types and the FEC codes are well understood. Moreover, commercial off-the-shelf (COTS) hardware
implementations are widely available. Adopting these standards will help expand the industrial base for MILSATCOM,
as well as reduce the development risk of the PTW, which is
very important in achieving cost savings.
The current protected waveform uses a static resource allocation approach. In this design, the satellite resource usage
is constrained, because it is set up as a circuit that meets the
strategic user requirement for guaranteed service through
dedicated lines. The PTW uses DRA, which is optimal for
efficiency and maximizes the system throughput. The DRA
will be performed by the system controller, who can originate the resource changes from the satellite (for processed
satellites), or from the ground hub (for transponder satellites), depending on the system architecture. This dynamic
allocation style is capable of performing the appropriate
communication mode selection, time, and bandwidth as-
signments based on link conditions and traffic requests. For
example, the data rate can be dynamically reduced from 8 to
1 megabits per second if severe weather or jamming is encountered, or can maintain 8 megabits per second by assigning more resources on the satellite or ground hub as needed.
Another important feature of the PTW is that it provides
seamless support to mobile terminals. Typically, multibeam
antennas for satellite payload designs are used to increase
antijam protection in a theater coverage area. Extensive
acquisition and beam handover protocols have been defined
to facilitate seamless communication when mobile terminals
(PCOTM and RPA) are moving out of the serving beam and
into another beam without interruption of communication.
Protected Tactical Service System Concepts
The Space/Hub
There are four major types of MILSATCOM system architectures: hub-spoke pure transponder (PT), hub-spoke dehop/
rehop transponder (DRT), partially processed (PP), and fully
Transponder Satellite Architecture
Ground hub
(virtual payload)
Network
interfaces
Gateway
Global
information
grid
Virtual payload
Antenna coverage areas
TRANSEC
Baseband processing
Terminal 2
RF front end
Terminal 1
Hub antennas
Timing unit
Layer 2 switching
System controller
Resource manager (DRA)
Mobility manager
Network manager
Encryption/
decryption
A notional hub-spoke dehop/rehop transponder architecture.
processed (FP) systems. Each of these satellite system architectures offers pros and cons. For example, conventional
PT systems are simply “bent pipe” payloads—they convert
uplink carrier frequencies to downlink carrier frequencies
for transmission of information without offering onboard
processing, such as demodulating and/or decoding for the
received uplink transmissions.
Aerospace has developed government reference architectures (GRAs) of four types of payloads and the protected
tactical service (PTS) system concept, created various
scenarios (theater, dispersed, jamming, and mobility) to
evaluate multiple system designs, developed requirements
for broad agency announcement studies, provided capacity
analysis of GRAs against the benign and contested scenarios
to perform system trade-offs, provided technical direction to
space contractors, and reviewed contractor payload designs
and performance analysis. The three space contractors working this effort provided useful and multiple design concepts
with affordable cost estimates. The U.S. government is now using this technical and cost information to support the current
Department of Defense MILSATCOM alternative of analysis.
In the PT architecture the satellite cannot perform channelization and routing of information without incurring the
heavy weight and high-power consumption of analog and
digital components. To offset this, a ground hub is used in a
double-hop transmission mode to perform various virtual
payload functions, such as routing, channelization, demodulation, forward-error-correction decoding, retransmission,
dynamic resource allocation, and hub assistance for disadvantaged user terminals. A source-user terminal sends traffic
back to the hub via the return link (user-to-satellite-to-hub)
where routing is applied and retransmitted using the forward
link (hub-to-satellite-to-user) in a second hop transmission
that travels over the bent-pipe payload and onto the destination user terminal(s). This hub-spoke–type architecture
requires a double-hop delay for user-to-user communications. Normally, a commercial PT system will not provide
antijam capability. However, this traditional, nonhopping
modem can be replaced by a PTW modem with antijam
functionality. The terminal can then resist the mobile and/
or transportable jammer. This solution is the most affordable
way to provide antijam capability to today’s wideband users
because the new modems are not expensive.
In the PT architecture, since the bent pipe repeater
translates the full frequency hop transponder bandwidth
from the uplink to the downlink frequency band, retransmission of the received uplink signals includes any jamming,
if present. A fraction of the downlink transmission power is
then devoted to the retransmission of uplink jamming falling within the transponder bandwidth, which is, in turn, a
power-robbing effect. Thus, the tolerable jammer power level
of the PT architecture is limited by power loss.
In DRT, the uplink frequency hop is dehopped and filtered
to a desired signal bandwidth that is much more narrow than
the hopping bandwidth and is then rehopped for the downlink frequency translation. There are two purposes for this
filtering effect: first, only that portion of the uplink jamming
falling within the transponder bandwidth is retransmitted
with the desired signal on the downlink; second, the filtering
operation provides noise rejection prior to amplification. The
DRT architecture requires a ground hub similar to the hubspoke PT architecture. The main advantage of a DRT payload
over a PT payload is improvement in antijam capabilities and
spectrum use without multiple ground hubs.
An FP payload is an architecture in which uplink signals
are dehopped, demodulated, and decoded on the satellite.
Onboard digital processing is then performed by the system
controller within the payload, which enables capabilities
such as network resource allocation, control and packet
switching, and routing. The downlink signals to user terminals are re-encoded, remodulated, and rehopped on the
satellite for transmission.
In the FP architecture, the uplink and downlink FEC and
modulations need not be the same, thereby enabling adaptive dynamic resource power and bandwidth allocation. This
is a single-hop architecture that does not require the use of a
terrestrial hub because the system controller is on board the
satellite. This architecture style requires a payload with complex on board digital processing capabilities. The fully processed payload terminates the uplink at the payload. Thus,
it can eliminate any uplink jammer power-robbing effect
present in the transponder. Moreover, the fully processed
payload provides increases in satellite capacity compared
to the traditional satellite transponder approach without
the hub-spoke architecture, while providing true full-mesh
single-hop multicast connections across all user terminals.
The fully processed payload is also superior in terms of resiliency, connectivity, and antijamming in comparison to the
hub-spoke transponder-based approaches.
The PP architecture is intermediate in complexity
between the single-hop fully processed payload and the
double-hop transponder payload. In a PP payload, the uplink signal is dehopped and demodulated, but FEC does not
occur. The signal is decoded, remodulated, and rehopped
for downlink transmission. The cost difference between a PP
and FP payload is negligible; however, a PP payload cannot
provide the extensive network flexibility and performance of
a FP architecture.
Different system architectures provide different levels
of protection, capacity, and cost. The four communication
architectures described can be implemented on free-flyers
and/or on hosted payloads depending on mission requirements. For example, the FP payload may be selected for
missions requiring defeating a large jammer. A DRT, on the
other hand, may be selected because of user desire to defeat
a transportable jammer.
A key feature of PTW is that it is agnostic to different
satellite communication system architectures with common
enterprise ground network infrastructures. This unique PTW
feature makes it interoperable for different protected tactical
users and their various system architectures and flexible to
different mission requirements. The PTW system can be built
over many years, delivering incremental capability, performance, and protection. This approach offers an innovative and
revolutionary solution for future MILSATCOM systems.
Terminal Transition
PTW is designed to be coupled with the mature current
protected waveform and existing commercial standards,
therefore allowing all of the contractors (space and terminal) to be able to produce brass board modems with PTW
functions within 10 months of contract start time in Phase I.
Boeing has demonstrated multiple channel functions using
PTW modems over a ViaSat Ka-band transponder satellite and WGS. L3 Communication West has successfully
demonstrated the key features of PTW modems over Intelsat
(Galaxy 18). Raytheon has demonstrated the PTW modem
over WGS satellites using Navy terminals.
The architecture-independent nature of the new waveform allows for its use over existing commercial and military
transponded satellites. This means existing unprotected
terminals could achieve a good level of protection over the
same satellites they use today by swapping out their current
modem with a PTW modem. Technically, one could put a
PTW modem in a wideband terminal or commercial terminal and enable the use of PTW, and its associated protection,
over a wideband or commercial satellite.
The majority of the terminal cost is in the radio frequency components. This study effort has shown that the modem
cost is about 6 percent of the total terminal cost. Therefore,
the most affordable near-term way to acquire antijam capability is via modem swapping from nonhopping modems to
PTW antijam modems. The Air Force, Army, and Navy are
interested in the modem swaps to avoid costly new terminal
development. Because the PTW is frequency agnostic, it
can also be extended to the extremely high frequency (EHF)
band (two gigahertz hopping bandwidth instead of one
gigahertz in Ka) in the future. This will reduce the problem
of satellite and terminal programs not being synchronized.
The terminal transition from commercial Ku band to highbandwidth Ka band or from military Ka band to EHF will be
much smoother too.
Ground Gateway and Network Development
One recurring theme of improving affordability of protected
tactical MILSATCOM is the careful consideration of the
trade-offs associated with allocating functions between space
and ground systems. Offering functionality that uses ground
components may improve affordability because size, weight,
and power constraints are not the concern that they are
on systems that need to function in space; nor are spacehardened components needed on ground systems. There is
also more ready availability of off-the-shelf components for
ground systems.
Another substantial consideration relates to the support
of current users on future systems, that is, backward compatibility. Here, one promising approach moves some of the
current functions in space to the ground via the use of a set
of gateway facilities.
A gateway of this type must provide secure and reliable
connectivity between protected tactical MILSATCOM users
and other networks. These networks include the Defense
Information Systems Network (DISN); services and connections with Advanced Extremely High Frequency (AEHF)
users; and interconnections with other tactical service
networks, such as the Army’s Warfighter Information Network–Tactical (WIN-T), and the Navy’s Automated Digital
Network System (ADNS).
Thus, the interfaces of the gateway must dovetail with the
operational requirements of existing systems, as well as with
their various approaches to information assurance. Like the
other segments of the system, the gateway must interface
with a management system, as well as implement appropriate information assurance controls for its own operations.
One approach to developing the gateway interface involves using a diverse set of networks that employ Internet
Protocol (IP) as a common denominator. Increasingly, military networks are in fact IP networks, and these networks
have established approaches to information assurance for
the transfer of their communications. Indeed, the gateway
should be able to reuse these approaches if the satellite communications services provided allow for interconnection of a
user’s IP equipment. For example, a satellite service providing transit of a layer two-packet switch would support this
type of interconnection across a wide variety of networks.
In this concept, the gateway system is largely reduced to
an integration of off-the-shelf equipment, provided for and
operated by individual users. In other words, it is a “bringyour-own-router” approach to the gateway interface. While
this concept appears promising, the ultimate design must be
considered across many factors, including packet overhead,
applicability of off-the-shelf components, security considerations, and support for advanced services, such as traffic
management, mobility, and efficient multicasting.
Mission Management
The Mission Management Subsystem (MMS) encompasses
all of the operational and logistical functions needed to
manage protected tactical MILSATCOM. These include
communications planning, network management, satellite
and mission operations, and monitoring, as well as support
to any training and maintenance activities.
Here, the approach to affordability relies on integrating
commercial-like tools and processes into a MILSATCOM
regime. This includes employing commercial and industry
standards, tools, operational practices, and approaches to
development across the entire lifecycle of the system. Moreover, the approach must reconcile these established practices
with the need to provide some level of consistency with current and projected MILSATCOM processes.
The operation supports standards of the Telecomm
Management (TM) Forum, which offers a potential set of
industry standards around which MMS functions could
be built. TM Forum is a nonprofit organization that brings
together the world’s largest service providers, network operators, software suppliers, and system integrators. The TM
standards complement the network management standards
common to industry networks, e.g., those developed by
the Internet Engineering Task Force (IETF). Nevertheless,
unlike IETF standards, TM Forum standards do not ensure
technological compatibility. Instead, the standards codify
business processes, information models, and operational
support functions. Using these standards could help in the
development of consistent requirements with semantics well
understood by a broad section of industry.
While use of off-the-shelf components undoubtedly reduces development costs, a future MMS will likely require some
amount of software development and tailoring for adequate
interface with the diverse set of MILSATCOM user communities. Here, the ability to perform integration activities early
on, and to sufficiently manage relationships with off-the-shelf
vendors, will play a critical role during development.
Information Assurance
The information assurance needs of protected tactical services must account for a diverse set of users who will operate
with varying types of information protection requirements.
The security requirements for next-generation protected
tactical services have been derived from an analysis of many
user scenarios, including those required by the Army’s
PCOTM and at the halt (ATH) systems, the Air Force’s
remotely piloted aircraft, Navy ships and submarines, and
special operations forces.
The terminal cryptographic implementation is another
essential element of the new protected tactical services and
provides the basis for the frequency hopping from which
these services enjoy antijam capabilities. Further, the cryptographic implementation provides the basis for the transmission security cover function, which is used for traffic flow
and is part of the terminal logon requirement. Much attention has been focused on the cryptographic implementation,
with particular interest in the Army PCOTM terminal end
cryptographic unit (ECU).
The terminal ECU is particularly interesting because its
DRT Satellite Architecture
Dehop/rehop transponder
Return link
Hub/gateway
Forward link
Ground
processor
Global
information
grid
Network interfaces
Three gimbal dish
antennae coverages
Theater
antenna
coverage
Earth coverage antenna
User terminal
Hub/gateway
• Downlink: Dual polarization
(1 GHz super high frequency bandwidth
on each polarization)
• Uplink: 2 GHz extremely
high frequency bandwitdth
Mission
management
system
Terminals with frequency hopping
Uplink: 2 GHz extremely high frequency bandwidth
Downlink: 1 GHz super high frequency bandwidth
Satellite and gateway
controller
PTS unique
General operations
manager
shared
An example of a DRT satellite architecture.
requirements are somewhat unique. The Army Terminal
Program Office has stated it wants a completely unclassified while operating terminal. Meanwhile, other users have
requirements for the ECU to be operated with secret-level
transmission security key material. This leads to the unique
requirements of keyed at secret, yet operational at unclassified. This may be attained through the use of current cryptographic certification processes. A successful implementation
here will likely be a pathfinder for future efforts wanting the
same results.
The PTW is envisioned to be similar to other national
security systems in that it will likely be subjected to cyberattack. It is anticipated that the PTW will be developed and
operated consistent with the security controls specified for
other DOD systems.
Conclusion
Since late 2011, the MILSATCOM community (the government, FFRDCs, TPOs, and contractors) have made good
progress toward the goal of developing new concepts for
future PTS systems that will meet warfighters’ needs identified in JSCL for performance and protection in the contested
environment while remaining affordable.
Aerospace has assisted the U.S. government in achieving these goals and has been a significant technical leader
and contributor in developing PTW requirements; GRA
designs of the space, ground, gateway, and mission manage-
ment subsystems; and network and information assurance
architectures.
Aerospace has provided in-depth technical analysis and
directions to the MILSATCOM community and to contractors during the latest phase of the study, and has assisted
the U.S. government in establishing the future acquisition
strategy of PTS.
The contractors have successfully completed PTW compatibility testing at the Massachusetts Institute of Technology/Lincoln Labs in July/August 2014 and three contractors
(Boeing, L3 Communication West, and Raytheon) have
already successfully performed over-the-air testing, proving
that PTW is the future waveform for tactical missions.
Acknowledgements
The authors would like to thank Tom Hopp, Robert Liang,
Steve Schmidt, James Stepanek, and Milton Sue for their
contributions to this article.
Applying Systems Engineering to
Manage U.S. Nuclear Capabilities
The Aerospace Corporation’s expertise in program systems engineering and integration is being applied to
nuclear programs for the National Nuclear Security Administration.
Matthew J. Hart, James D. Johansen, and Mark J. Rokey
T
he National Nuclear Security Administration (NNSA)
ensures the United States sustains a safe, secure, and
effective nuclear deterrent. Through the Office of
Defense Programs, the mission of the Stockpile Stewardship and Management Program is to maintain the active
stockpile, extending the life of weapons systems through the
application of science, technology, engineering, manufacturing, and weapons dismantlement. Through the Office of
Defense Nuclear Nonproliferation, the NNSA works closely
with laboratories and the private sector to detect, secure, and
dispose of dangerous nuclear and radiological material, and
related weapons of mass destruction (WMD) technology
and expertise.
The U.S. Congress created the NNSA in 2000 as a separately organized agency within the Department of Energy,
responsible for the management and security of the nation’s
nuclear weapons, nuclear nonproliferation, and naval reactor
programs. In 2002 the NNSA reorganized, removing a layer
of management by eliminating its regional operations offices
in New Mexico, California, and Nevada. NNSA headquarters
retained responsibility for strategic and program planning,
budgeting, and oversight of research, development, and nonproliferation activities. More recently, the NNSA requested
that The Aerospace Corporation conduct an external and
independent review of its management practices, systems
engineering, and mission assurance in a number of important areas.
When Aerospace was founded in 1960, its initial contract
was with the Air Force Ballistic Missiles Division, supporting
the development of advanced nuclear missile technologies
and missile defense programs. During the 1970s and 1980s,
Aerospace had important roles in planning major infrastructure and technology projects for the Department of Energy.
Many of the technologies found in spacecraft and launch
vehicles are also commonly used by the nuclear security
enterprise. Aerospace has remained active in these areas and
continues to support them today.
Office of Defense Programs
In 2011 Aerospace conducted a series of independent studies, at the request of Defense Programs, focusing on the
systems engineering and mission assurance management
processes applied to its major nuclear weapons refurbishment programs, known as life-extension programs. The
NNSA employs an end-to-end acquisition process, referred
to as the Phase 6.X Process, which differs in some ways
from DOD acquisition practices. Moreover, the relationship
between the NNSA, as a partner with the nuclear weapons
laboratories and production sites, differs from that of the
government customer-prime contractor relationship that
exists for DOD acquisitions. In light of these differences,
Aerospace approached this task by taking a fresh look at the
NNSA’s way of doing business and provided value-added
• Defense programs: maintain a safe, secure, and reliable nuclear
weapons stockpile to help ensure the security of the U.S. and its allies,
deter aggression, and support international stability.
• Defense nuclear nonproliferation: detect, prevent, and reverse the
proliferation of weapons of mass destruction and promote international
nuclear safety.
• Naval reactors: provide the U.S. Navy with safe and effective
nuclear propulsion systems and ensure their continued safe and
reliable operation.
• Emergency operations: manage nuclear and radiological emergency
response capabilities within the U.S. and abroad.
The National Nuclear Security Administration’s mission areas.
observations and recommendations within the context of the
existing NNSA acquisition culture and structures.
Aerospace assembled a team of senior personnel with
knowledge of complex systems acquisition and development,
systems engineering, integrated lifecycle management, mission assurance, and program execution. The team focused on
five areas: staffing and workforce, cost and schedule estimating, budget management, technology and manufacturing,
and program systems engineering and risk management. The
team interviewed key NNSA federal managers and staff, and
personnel at the national laboratories and production sites
across the nation. The team also interviewed DOD stakeholders within the Navy and Air Force. The team reviewed
programmatic and technical information from the site visits,
NNSA-provided information, and other government reports
and audits.
The Aerospace report focused on the need for an organizationally independent systems engineering and integration (SE&I) function at the enterprise level to help manage
requirements, provide technical insight, and support the
consistent use of best practices across the enterprise. Other
recommendations were made, including formalizing the
decision process for mitigating risk and establishing a strong
technical and programmatic baseline management process
for NNSA acquisition programs.
The report helped the Office of Defense Programs to
make decisions on reorganizing and creating two new
groups. One group would focus on major acquisitions, such
as weapons life extension programs, and the other would
provide the independent SE&I function. Aerospace assisted
in identifying candidate SE&I organizational structures,
roles and responsibilities, and staffing requirements.
Today, Aerospace is providing experienced engineering
advisory support to the Defense Programs SE&I in Washington, D.C., and Albuquerque, New Mexico, which includes
program systems engineering for the B61 gravity bomb lifeextension program, independent technical studies and risk
assessments, and the development of systems engineering
policy and practices to benefit the enterprise.
The Space-based Nuclear Detonation Detection mission is supported with hosted
payloads on Air Force satellites, such as GPS.
Source Evaluation Board
The nation’s nuclear weapons laboratories are managed, on
behalf of the NNSA, through management and operating
(M&O) contracts to large private sector companies, universities, and nonprofit organizations. As part of the work in reviewing NNSA management processes, Aerospace was asked
to review and comment on the current M&O contracting strategy. The Aerospace team met with NNSA source
evaluation board representatives and gathered background
information on the agency’s current contracting and source
selection approach, and supporting documents and example
artifacts from previous competitions.
The study team provided the NNSA source evaluation
board with information on acquisition strategy best practices, such as structuring statements of work, contractual
deliverables, and invoices to manage contractor performance
and ensure access to technical and programmatic information needed to monitor contract performance.
Office of Defense Nuclear Nonproliferation Research
and Development
One of the gravest threats the United States and the international community face is the possibility that terrorists or
rogue nations will acquire nuclear weapons or other WMDs.
NNSA’s Office of Defense Nuclear Nonproliferation Research
and Development supports the multiagency United States
The phase 6.X process that the National Nuclear Security Administration uses to
manage life-extension programs for the United States nuclear weapons stockpile.
Nuclear Detonation Detection System (USNDS) in detecting
nuclear detonations around the world. The office supports
this effort through research and the development of spacebased sensors to monitor for nuclear events and provide
global awareness of possible nuclear detonations.
The USNDS sensors are hosted on military satellite
systems managed by the Air Force, such as the Global Positioning System (GPS). As these satellites undergo planned
block upgrades or transition to other programs, the effects
of such changes on the USNDS mission must be considered.
The Office of Defense Nuclear Nonproliferation Research
and Development conducted an analysis of alternatives to
assess future USNDS sensor architecture alternatives, which
considered different numbers and types of sensors and nextgeneration sensor technologies and their impact on cost,
schedule, and performance.
The office asked Aerospace to participate as an independent third party to provide independent cost and schedule
assessments, risk assessments, and technical advice concerning systems architecture, host spacecraft, and sensor
technology. Aerospace’s extensive knowledge of the host
spacecraft allowed a deeper understanding of the technical
and program implications of the different sensor alternatives
and their risks to USNDS and the host missions.
Aerospace brought in experts knowledgeable in the
host space systems and spacecraft requirements to confirm
key assumptions in the study. Aerospace helped the NNSA
understand the system drivers on the current host platforms
and constellations and the effect that changing spacecraft
requirements would have on the sensor designs. The host
spacecraft’s planned availability date was also important in
defining the development times and need dates for a new
sensor. Aerospace applied the cost and schedule estimating
methodology developed for assessing NASA science instruments to estimate the development and production costs
and readiness dates for the alternative sensor architecture
options.
Aerospace’s analysis provided the Office of Defense
Nuclear Nonproliferation Research and Development with
information on the cost and availability of the different
architecture options. This was combined with system and
Courtesy of NNSA and the National Archives
A timeline of nuclear weapons development and historical information.
architecture performance assessments to help the office
select affordable future architectures that meet operational
requirements and stakeholder needs.
The Office of Defense Nuclear Nonproliferation Research
and Development identified the need for an independent
architecture-level simulation capability to predict system
performance so that it could assess current and nextgeneration USNDS systems’ ability to meet requirements.
The Distributed Infrastructure Offering Real-time Access
to Modeling and Analysis (DIORAMA) software tool will
provide a robust physics-based modeling and simulation
capability and will be validated, well documented, and accessible for use by the entire USNDS community.
NNSA has asked Aerospace to colead the independent
verification, validation, and accreditation effort of DIORAMA, along with Lawrence Livermore National Laboratory,
and the Air Force Institute of Technology.
The verification component will determine if DIORAMA’s modeling and simulation implementation and its
associated data accurately represent the software developer’s
conceptual descriptions and specifications. The validation
component will determine if the performance model and its
associated data provide an accurate representation of the real
world from the perspective of its intended uses—in this case,
detecting nuclear detonations and processing detection data.
As part of this effort, the team will monitor the development
of test plans, develop independent system scenario testing,
and monitor regression testing as functional capabilities are
added and the software matures.
Accreditation will be official certification that the performance model and its associated data are acceptable for
use by NNSA and its affiliates. Accreditation also certifies
that the software has met all requirements and performance
specifications, along with security concerns and maintainability. This accreditation will be based on the integration of
verification and validation findings that will be delivered and
reviewed throughout the software development lifecycle.
As part of the NNSA’s ongoing efforts to improve overall
performance, the Office of Defense Nuclear Nonproliferation
Research and Development has established its own independent SE&I functions to provide systems engineering and
mission assurance support to the office’s sensor development
activities. Aerospace is providing independent technical and
programmatic advice, risk assessments, and subject matter
expertise to aid in resolving technical problems during the
development process.
Conclusion
Support to the NNSA demonstrates the application of Aerospace technical and acquisition know-how to the broader
national security enterprise. Aerospace’s ability to offer
sound, unbiased technical advice, and apply its programmatic expertise to complex acquisition problems, provides
benefits to the government that go beyond national security
space.
RESEARCH HORIZONS
Independent R&D at Aerospace
Strained Silicon Photonic Devices for Optical Modulation
The demand for compact, low-cost components for optical
communication, signal processing, and optical sensing is
driving the rapid development of silicon photonics. Silicon
is a chemical element used in semiconductor electronics and
integrated circuits and is the basis of most of today’s computers. Crystalline silicon can also be used to make photonic
components and can be used to integrate electronics with
photonic functionality on a single chip-scale platform.
Most of today’s optical systems rely on discrete optical fiber
components or free-space optical elements. However, these
components take up a lot of space, therefore limiting the
overall capacity and functionality that can be engineered
into a small volume. National security space applications
will benefit from the development of next-generation integrated high-speed optoelectronic circuitry based on silicon.
The benefits of using silicon components on these systems
include increased bandwidth capability, smaller physical
footprints, and reduced power consumption.
A key building block in any photonic system is the electrooptical modulator, an optical waveguide device that imprints
an electrical waveform or data stream onto an optical carrier.
Analog waveforms or data bits may be encoded by shifting the
amplitude or phase of the light that passes through it with this
device. The phase or amplitude shifts are generated by the applied input electrical waveform that alters the refractive index
of the modulator material (electro-optic effect). Because of the
cubic symmetry of the silicon crystal lattice, however, this material does not naturally exhibit this effect. Other techniques,
such as charge-carrier depletion and thermo-optic tuning,
have been used to modulate the refractive index of silicon, but
Si phase modulator response
1.2
Phase response (radians)
1.0
0.8
0.6
0.4
0.2
0.0
05
0
100
150
Applied voltage (Vpp )
Phase response of a strained silicon modulator.
200
250
Scanning electron microscope image of a cross section of the device showing a one
micrometer wide buried silicon waveguide.
these have limited data bandwidth capabilities and consume
excessive electrical power.
By introducing strain into the silicon crystal structure,
silicon can exhibit electro-optic activity. Aerospace researchers are exploring this strained silicon approach. Andrew
Stapleton, a member of the technical staff, Photonics Technology Department, is the principal investigator of a team that
is using strained silicon to make electro-optical modulators.
The research team includes Peter DeVore, Heinrich Muller,
and Todd Rose, all of the Photonics Technology Department.
These team members have supported several national security
space programs in which lithium niobate optical modulators
have been used. The team is applying findings from this work
to its research into silicon straining techniques. The researchers have found that the silicon modulators they are developing
do not appear to degrade in the space environment, unlike
lithium niobate modulators, which are currently being used
for this application.
To achieve strain in silicon waveguides, a thin layer of
silicon dioxide is deposited over the crystalline silicon optical
waveguides. The strained silicon modulators are fabricated at
Aerospace with commercially available silicon-on-insulator
wafer substrates. These wafers have a 0.26-micrometer-thick
silicon device layer over a 2.0-micrometer layer of silicon dioxide. A thicker, silicon substrate lies under the oxide. The top
silicon layer is sufficiently thin to support a single transverse
optical mode of light at a wavelength of 1.5 micrometers. Before depositing the dielectric straining layer onto the device,
the waveguide patterns are first defined in a photoresist mask
on top of the wafer substrates. Then, a sulfur hexafluoride
plasma etching process is used to transfer the waveguide
patterns from the mask to the underlying silicon
layer, and the photoresist mask is removed. Once
the optical device layer is fabricated, a 1.5-micrometer silicon dioxide top layer is deposited
in a plasma-enhanced chemical vapor system at
300 degrees Celsius. Because of the difference
between the coefficients of thermal expansion for
silicon and silicon dioxide, the silicon waveguide
core is strained as the structure cools to room
temperature.
Because strain distorts the silicon crystal
lattice’s symmetry, strained silicon exhibits an
electro-optic effect so that the index of refraction
of the crystal waveguide, and hence the phase
of the transmitted light, can be controlled with
an applied electric field. “The first experiments involved simple optical phase modulators in which
gold electrodes were deposited on the waveguide
samples,” said Stapleton. The researchers placed
the silicon modulators in a free-space optical
interferometer, quantifying the optical phase
change under various voltages. This technique allows for estimating the strained silicon’s nonlinear
susceptibility, a key performance metric.
Numerical simulations using COMSOL (a software program for modeling and simulating scientific and engineering problems) indicate that 2.5 percent of the total voltage
was applied across the silicon waveguide, with the bulk of
the voltage dropped across the electrically insulating oxide
above and below the waveguide core. From this analysis, the
nonlinear susceptibility was estimated to be 2.7 picometers
per volt. While this value is less than that of gallium arsenide
or lithium niobate (99 and 360 picometers per volt, respectively), further improvement is expected if the magnitude of
the strain in the waveguide can be increased.
For this reason, the Aerospace research team has been
working to understand and quantify strain in fabricated
devices under various waveguide geometries and processing conditions. One analytical technique being used is
micro-Raman spectroscopy. In this technique, light from a
blue laser is focused on the waveguide sample, exciting the
silicon crystal lattice’s optical phonon modes. The scattered
light emitted from the sample surface is then collected and
analyzed under a microscope. Unstrained silicon has a distinct characteristic Raman peak at 520 waves per centimeter.
When the analyzed sample is a strained silicon waveguide,
the Raman peak shifts to either a higher or lower wave number (corresponding to compressive or tensile strain, respectively). The magnitude of this shift can be used to quantify
the level of strain in the waveguide.
Raman spectra collected from a region of the unstrained silicon substrate (solid dots)
and a one micrometer wide strained silicon waveguide (open dots). The lines are numerical fits to a Lorentzian profile.
“The silicon waveguide samples studied with microRaman spectroscopy were found to be under tensile strain,”
said Stapleton. Similar Raman data from other waveguides
with different widths indicates that the magnitude of this
strain increases as the width of the waveguide is reduced. For
example, the strain in 0.5-micrometer-wide waveguides was
approximately twice the strain observed in 1.0-micrometerwide waveguides. These findings indicate that the electricalto-optical conversion efficiency (i.e., gain) of strained silicon
modulators can be significantly improved by fabricating
devices with narrower waveguides.
In addition to developing a silicon optical phase modulator, the research team has demonstrated a fully integrated
optical intensity modulator containing two strained silicon
phase modulators along with waveguide splitters and combiners in a Mach-Zehnder interferometer configuration. This
demonstrates that strained silicon devices can be integrated
with other optical components to form more complex optical systems on a single chip.
While the development of strained silicon modulators is
very much in its infancy, this approach points to the feasibility of devices that are more chemically inert and tolerant of
space environments compared to current state-of-the-art
lithium niobate modulators. Further work will need to focus
on improving the overall modulation efficiency of strained
silicon modulators before this class of devices can be considered a viable substitute.
RESEARCH HORIZONS
Independent R&D at Aerospace (continued)
Toward a Better Understanding of Electrostatic Discharge
If current spacecraft power trends toward increased solar array size and operating voltage continue, the risk of on-orbit
performance losses from electrostatic discharge (ESD) will
also increase. Without proper electrical charge mitigation,
solar arrays and other satellite components are subject to
significant charging in the space environment. Such charging
can lead to substantial and frequent electrostatic discharge,
which is a sudden flow of electricity between two differently
charged objects, sometimes causing an on-orbit anomaly.
Spacecraft ESD is a complex phenomenon that can disrupt normal operations and even destroy solar array circuits
and other electronics. Studies have been conducted since the
1970s to expand the awareness and understanding of these
events, leading to the development of analysis tools such as
NASCAP-2K (NASA/Air Force Research Laboratory [AFRL]
spacecraft charging analysis program). This next-generation
spacecraft charging analysis code can create realistic geometric models, simulate charging, and calculate and display
surface potential/currents, space potentials, and particle
trajectories.
As sophisticated as many of these analysis tools have
become, they still lack some of the critical parameters and
physics needed to make accurate predictions for ESD in
the space environment. Decades of laboratory tests have attempted to establish electrical charge dynamics and propagation, but there is limited consensus on the basic mechanisms
and fundamental quantities of these effects, including propagation velocity, which helps to determine the magnitude of
current transients. Spacecraft developers therefore continue
to rely on the testing of components in a simulated space
environment to create high-performance designs.
In an effort to develop more accurate prediction techniques, Jason Young, a member of the technical staff, and
Mark Crofton, a senior scientist, both of the Propulsion Science Department at The Aerospace Corporation, have been
conducting research to better understand the dynamics and
scaling of electrostatic discharge on large satellite components, including solar arrays and multilayer insulation. They
are using ESD1 for the testing, which is Aerospace’s new
space-simulation vacuum facility, built to carry out electrostatic discharge testing in a more optimized way (most of the
historical Aerospace work was performed in the EP2 electric
propulsion chamber).
“Although we know a great deal about how surface charge
builds up on spacecraft components, many details of how
that charge is released are uncertain. This makes it difficult
to properly predict the shape, peak amplitude, and duration
of the discharge current for array-size structures, which is
View from end port of ESD1 vacuum chamber in D1. The US Round Robin Coupon
from NASA GRC is mounted inside for inverted gradient charging tests.
the ultimate determinant for risk of component damage or
failure,” said Young.
Over the past several decades, the entrenched paradigm
for electrostatic discharge has been the brushfire model.
According to this model, an ESD current radiates outward
at a constant speed from a single central arc point, instantly
clearing all surface charge along the propagating front. As
the electrical charge is cleared from dielectric surfaces like
coverglass, currents are generated on adjacent conductors,
like solar cells.
The brushfire model assumes the propagation of ESD
occurs at a fixed speed that is independent of surface morphology or composition. However, experiments on complex
test components that measure this propagation have often
produced varied results.
Young and Crofton’s research has so far revealed that ESD
is much more complicated than the findings of the brushfire
model. Instead of using a complex, reduced-scale solar array
coupon, which is the standard component for electrostatic
discharge testing, the researchers have used a one-squaremeter panel of concentric ring electrodes covered in Kapton,
a polyimide film used in flexible printed circuits. The panel
has been irradiated with electrons to create a net positive
surface charge that is similar to conditions found in geosynchronous Earth orbit during an extreme space weather
event. Electrical arcs were generated from a defect at the test
panel’s center, resulting in induced electrical currents on the
ring electrodes.
“By measuring these currents, we could determine the radial progression of an electrostatic discharge event. The data
more variations in the ring
panel’s surface and morphology
and the composition of the electrical arc initiation point. The researchers are hoping to correlate
the ring electrode current patterns using external diagnostic
instruments such as Langmuir
probe arrays and imaging spectrometers. Once these instruments are calibrated, they could
then be transitioned to test more
complex satellite components,
such as solar array coupons and
multilayer insulation sheets, in
which the electrode patterns are
not as optimized for measuring
electrical current.
The Aerospace researchers
are also participating in a series
Surface charge neutralization current for a single ESD event as a function of time and radial distance from inception
of tests with AFRL and other
point on the ring coupon. (Inset) Image of the Kapton-covered ring coupon.
ESD researchers around the
country. In similar setups at multiple facilities, various solar array
show that instead of a sequential removal of charge from
coupon designs are being tested to measure ESD propagathe innermost to outermost ring, charge removal begins on
tion characteristics in simulated geosynchronous and low
all rings nearly simultaneously, with the charge removal on
Earth orbit charging environments. The team is also working
more distant rings taking more time. The data also show that
with a pulsed laser that can produce ESD on demand. Interpeak current amplitude is not proportional to ring radius,
estingly, the researchers have found that the ESDs produced
which is in contradiction to the brush fire theory,” said
at specific intervals by the laser varied more significantly in
Young.
magnitude and duration than those produced spontaneously.
The researchers have also found that during an ESD
This technique is anticipated to produce insights into ESD
event, electrical current grows more or less linearly with
initiation thresholds and electrical arc rates.
time, along with brief, intermittent increases and decreases
Through the development and application of new apof current rapidly propagating from inner to outer ring
proaches
like these, the team hopes to augment the current
electrodes. Because of their proximity to the panel center
database
and
understanding of ESD in the space environand smaller surface area, the released charge fraction of
ment, improve qualification test procedures, and reduce the
inner ring electrodes changes more rapidly. As the remainrisk of disruptive on-orbit ESD events.
ing surface charge decreases, the electrode current declines
exponentially.
“These characteristics of electrostatic discharge are reminiscent of a diffusion process, which has important implications for components operating in space. Since electrostatic
discharge propagation has been found to be dispersive in
these tests, a peak anomaly current does not necessarily
increase linearly with distance, as was originally believed. In
fact, it seems to increase more slowly, suggesting more favorable scaling for large spacecraft components,” said Young.
Moving forward, Young and Crofton plan to introduce
RESEARCH HORIZONS
Independent R&D at Aerospace (continued)
Mobile Code and COAST: Potential Allies to Cybersecurity in the Cloud
Cloud computing presents an attractive option for hosting
digital services where storage and computational demands
may vary significantly over time. Computing clouds are
elastic infrastructures that can be quickly expanded or
contracted in response to variations in service demands or
computational needs. These modern clouds rely on virtual
machines to emulate the hardware and peripherals of physical servers with multiple virtual machines executing on a
single physical server. Modern large-scale clouds, offered by
commercial vendors such as Amazon, Google, and Microsoft, are provisioned on a massive scale. For example, the
Amazon cloud is estimated to contain approximately 500,000
high-performance physical servers, and the Google cloud is
believed to be significantly larger.
Government agencies can reduce costs by sharing a
cloud with other organizations and users, while the cloud
infrastructure transparently manages service load variations
behind the scenes. Ample cloud computing and networking
resources simplify the design, implementation, and deployment of critical information services, while spikes in service
demands can be accommodated within minutes. However,
these resources and the flexibility they offer come with a
price: this same massive cloud-computing infrastructure
can launch cyberattacks against other information services
within and outside the cloud.
Mobile code is a technology that allows the seamless
transfer of running computations from one network location to another, or equivalently from one virtual machine
to another, and therefore is an attractive complement to
cloud-based virtual machines. Mobile code simplifies the
construction and deployment of cloud-based services by
allowing programs to be dynamically moved to different
virtual machines as the cloud is expanded or contracted. In
addition, services using mobile code can be deployed on the
fly to modify or augment services in response to evolving
missions or the immediate, urgent demands of a cyberattack.
However, due to its easy deployment and flexibility,
mobile code is also a superlative tool for mounting attacks
against a system. Thus the same mobile code technology that
promotes system flexibility and adaptivity also puts systems
at considerable risk. Can the benefits of mobile code technology be enjoyed without increasing the risk of a cyberattack?
At a minimum, the mobile code and its supporting infrastructure must be secured against attack—a difficult and
vexing problem for which no compelling solution has been
articulated.
To counter these threats, Michael Gorlick, senior engineering specialist, Computer Systems Research Department,
and Richard Taylor, a professor of information and computer
sciences at the University of California, Irvine, are investigating mobile code options for securing against cyberattacks
that arise from within the cloud. Gorlick and Taylor have
developed COAST (COmputAtional State Transfer), an
architecture style that is based on mobile code for
Internet-scale network services where the mobile code itself
becomes a critical element in a coordinated defense against
cyberattacks.
“COAST is based on capability security, which fuses the
designation of a service and access to that service into a
single, unforgeable reference—a capability,” said Gorlick. The
COAST architecture prescribes cloud-based mobile code
systems with a set of simple yet powerful rules. It defines a
set of mechanisms that allow programs to defend themselves
against hostile or malicious visitors, halts communication
with ill-behaved programs in the cloud or network, and prevents unrecognized programs from communicating directly
with the COAST-based services residing within the cloud.
“COAST confines visiting mobile code with restrictive
functional, resource, and communication capabilities, defining what the mobile code can do, and limiting its resource
consumption and communication powers. The visiting code
has only the powers granted to it and nothing more,” said
Gorlick. For example, if a program is not explicitly granted
a capability to read a sensitive database, then it will not be
allowed access to it.
COAST denotes individual programs with capability
uniform resource locators (CURLs), which are the carriers for communication across a network. “These CURLs
are cryptographic structures that are impossible for any
other computation to guess, counterfeit, or modify without
being caught,” said Gorlick. Programs within COAST rely
on communication by introduction. For example, program
X cannot communicate with program Y unless it holds a
CURL explicitly allowing the communication. This communication by introduction helps to ward off denial of service
attacks, eliminates spurious communications, hinders theft
of service, detects the misuse of communications, assigns
blame, and revokes communication privileges as needed.
CURLs also enforce communication constraints, including
the total number of times that X can communicate with Y,
the maximum rate and bandwidth at which X can communicate with Y, and the span of time during which the communication is permitted. The mechanisms of mobile code can
enforce complex communication constraints that implement
temporal, spatial, and collaborative requirements.
Gorlick and Taylor have now implemented Motile, a
share, and manipulate realtime, high-definition satellite
video streams. Their research
suggests that COAST-based
architectures are feasible in
domains characterized by
multiple, continuous data
streams, including for satellite ground stations.
“One distinguishing
characteristic of the COAST
architectural style is its
complete indifference to the
actual location or precise formulation of mobile computations. In particular, Motile/
Island can execute on a
broad scale of platforms and
in a variety of network environments, from embedded
Controlling the propagation of capability among programs is critical to minimizing the risks of cyberattack.
single-board computers to a
cloud of virtual machines,”
mobile code programming language consistent with the
said Gorlick.
precepts of COAST, and Island, a decentralized, peering
Gorlick is also working with Larry Miller, principal eninfrastructure capable of safely executing mobile Motile progineering specialist, Software Engineering Subdivision, and
grams. Motile/Island resolve the conundrum of safe mobile
David Wangerin, Computer Systems Research Department,
code by repeatedly applying capability security at all levels of
to consider new spacecraft designs in which all spaceborne
a given infrastructure. The same capability security that proservices, including payloads, are implemented in the COAST
tects Island against errant or deliberately malicious Motile
architectural style. The researchers have found that mobile
programs also protects the infrastructure itself from cybercode has the potential to simplify many troublesome aspects
attacks. Both the Motile compiler and the Island infrastrucof spaceborne architectures, including autonomous fault
ture are written in Scheme, a programming language with
recovery, hot updates (updating onboard software without
a long history in mobile code experimentation. The Island
pausing or rebooting), and processor failure.
infrastructure is the service-oriented architecture equivalent
For example, automated responses can simply abandon
of service providers and consumers; a single “island” can
a processor if it fails, and by using mobile computations,
simultaneously act as both a provider and consumer.
reconstitute the services elsewhere within the spacecraft, on
“By embedding specific mobile code into CURLs, we can
another nearby spacecraft, or perhaps (real-time constraints
ensure that whenever program Y attempts to exploit a capapermitting) on the ground. A testbed infrastructure based on
bility designated for program X, its effort will fail. Controllow-cost, single-board computers is now being constructed
ling the propagation of capability among programs is critical
for prototyping common satellite bus subsystems such as
to minimizing the risks of cyberattack, and mitigating the
thermal control, electrical power distribution, and attitude
likely damage of an attack is a core element of our ongoing
control. Here, the challenges include adapting COAST to the
research,” said Gorlick.
rigors of spaceborne systems, recasting traditional embedded
Gorlick and Taylor are also exploring how COAST can
designs for mobile computations, and ensuring the effective
be used in a variety of space settings and domains, including
and timely execution of mobile computations on resourcefor the distribution and manipulation of high-bandwidth
constrained platforms.
satellite telemetry. COASTcast, a demonstration application implemented with Motile/Island, permits users to view,
BOOKMARKS
Recent Publications, Papers, and Patents by the Technical Staff
Publications _____________________________
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Environmental NanoSat Experiment,” AIAA 2012 SPACE
Conference and Exposition (Pasadena, CA, 2012).
W. A. Ailor, M. A. Weaver, et al., “Perspective on Reentry
Breakup Recorder Derived Concepts for Small Payload
Flight Experiments,” 44th AIAA Thermophysics Conference (San Diego, 2013).
J. Alexander, J. Betser, L. Florer, J. Nilles, P. Reiher, et al.,
“Improving the Security of Android Inter-Component
Communication,” Proceedings of the 2013 IFIP/IEEE
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J. Bannister et al., “A Design for an Internet Router with a
Digital Optical Data Plane,” Proceedings of SPIE—The
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J. Bannister et al., “An Optical Packet Switch Using ForwardShift Switched Delay Lines,” 2013 18th OptoElectronics
and Communications Conference Held Jointly with 2013
International Conference on Photonics in Switching (Kyoto,
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J. D. Barrie, P. D. Fuqua, M. J. Meshishnek, M. R. Ciofalo,
C. T. Chu, J. A. Chaney, R. M. Moision, et al., “Root Cause
Determination of On-Orbit Degradation of the VIIRS
Rotating Telescope Assembly,” Proceedings of SPIE—The
P. A. Bertrand, “Chemical Degradation of a Multiply Alkylated Cyclopentane (MAC) Oil during Wear: Implications
for Spacecraft Attitude Control System Bearings,” Tribology Letters, Vol. 49, No. 2, pp. 357−370 (2013).
J. Betser et al., “Innovation Acceleration for National Security Space,” AIAA 2012 SPACE Conference and Exposition
(Pasadena, CA, 2012).
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R. Bishop, A. Christensen, J. Hecht, et al., “The HICO
RAIDS Experiment Payload Mission,” Proceedings of the
1st Annual ISS Research and Development Conference (San
Diego, 2013).
R. L. Bishop et al., “Propagation of CubeSats in LEO Using
NORAD Two Line Element Sets: Accuracy and Update
Frequency,” AIAA Guidance, Navigation, and Control
(GNC) Conference (Boston, 2013).
R. L. Bishop, J. H. Hecht, R. W. Walterscheid, et al., “Altitude Profiles of Lower Thermospheric Temperature from
RAIDS/NIRS and TIMED/SABER Remote Sensing Experiments,” Journal of Geophysical Research: Space Physics,
Vol. 118, No. 6, pp. 976−982 (2013).
R. Bitten, D. Emmons, F. Bordi, et al., “Explanation of
Change (EoC) Study: Approach and Findings,” IEEE
Aerospace Conference Proceedings (Big Sky, MT, 2013).
R. Bitten, D. Emmons, M. Hart, F. Bordi, et al., “Explanation
of Change (EoC) Study: Considerations and Implementation Challenges,” IEEE Aerospace Conference Proceedings
(Big Sky, MT, 2013).
R. Bitten, E. Mahr, et al., “Assessing the Benefits of NASA
Category 3, Low Cost Class C/D Missions,” IEEE Aerospace Conference Proceedings (Big Sky, MT, 2013).
R. E. Bitten, D. L. Emmons, F. Bordi, M. J. Hart, et al., “Findings and Considerations from the NASA Explanation of
Change Study,” AIAA SPACE 2013 Conference and Exposition (San Diego, 2013).
R. E. Bitten, M. R. Hayhurst, D. L. Emmons, et al., “Phase E
Cost Analysis for NASA Science Missions,” AIAA 2012
SPACE Conference and Exposition (Pasadena, CA, 2012).
J. Betser et al., “Knowledge Management for Architecting
Space Systems,” AIAA 2012 SPACE Conference and Exposition (Pasadena, CA, 2012).
R. E. Bitten and E. M. Mahr, “Instrument Schedule Delays:
Potential Impact on Mission Development Cost for Recent NASA Projects,” International Geoscience and Remote
Sensing Symposium, pp. 5658−5661 (Munich, Germany,
2012).
J. Betser et al., “Managing the Next Wave of Information
and Communications Technologies: A Report on NOMS
2012,” Journal of Network and Systems Management, Vol.
21, No. 3, pp. 510−516 (2013).
R. E. Bitten, E. M. Mahr, et al., “Reducing Development
Risks in NASA Science Missions—Developing Instruments First,” AIAA 2012 SPACE Conference and Exposition (Pasadena, CA, 2012).
J. Betser et al., “Space Cyber Architecting Horizons,” AIAA
2012 SPACE Conference and Exposition (Pasadena, CA,
2012).
J. Blake, “SAMPEX and Relativistic Electron Microbursts,”
2012 American Geophysical Union Fall Meeting (San
Francisco, 2012).
J. Betser, K. Ferrone, G. Richardson, J. Penn, and S. Martinelli, “On-Orbit Servicing of Department of Defense
and National Security Space Assets,” AIAA 2012 SPACE
J. B. Blake et al., “A Nonstorm Time Enhancement of Relativistic Electrons in the Outer Radiation Belt,” Geophysical
Research Letters, Vol. 41, No. 1, pp. 7−12 (2014).
R. Bishop et al., “GEOScan: A Global, Real-Time Geoscience
Facility,” IEEE Aerospace Conference Proceedings (Big Sky,
J. B. Blake et al., “Nonstorm Time Dynamics of Electron
Radiation Belts Observed by the Van Allen Probes,”
Geophysical Research Letters, Vol. 41, No. 2, pp. 229−235
(2014).
J. B. Blake, P. A. Carranza, S. G. Claudepierre, J. H. Clemmons, W. R. Crain, Y. Dotan, J. F. Fennell, F. H. Fuentes,
R. M. Galvan, J. S. George, M. Lalic, A. Y. Lin, M. D.
Looper, D. J. Mabry, J. E. Mazur, B. McCarthy, C. Q.
Nguyen, T. P. O’Brien, M. A. Perez, M. T. Redding, J. L.
Roeder, D. J. Salvaggio, G. A. Sorensen, S. Yi, M. P. Zakrewski, et al., “The Magnetic Electron Ion Spectrometer
(MagEIS) Instruments aboard the Radiation Belt Storm
Probes (RBSP) Spacecraft,” Space Science Reviews, Vol.
179, No. 1-4, pp. 383−421 (2013).
J. B. Blake, S. G. Claudepierre, J. H. Clemmons, J. F. Fennell, T. P. O’Brien, D. Salvaggio, et al., “Science Goals and
Overview of the Radiation Belt Storm Probes (RBSP) Energetic Particle, Composition, and Thermal Plasma (ECT)
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Poloidal Standing Alfvén Waves through Drift Resonance
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in the Outer Plasmasphere Associated with SubstormInjected Electrons,” Geophysical Research Letters, Vol. 40,
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Local Acceleration of Relativistic Radiation Belt Electrons
by Magnetospheric Chorus,” Nature, Vol. 504, No. 7480,
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of Galactic Cosmic Ray Shielding with the CRaTER
Instrument,” Space Weather, Vol. 11, No. 5, pp. 284−296
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J. B. Blake, J. Mazur, et al., “Contributions of Primary Particles to Observed LET for the CRaTER Instrument on
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Modeling, Simulation and Analysis for Space Applications,” 2013 IEEE International Symposium on Electromagnetic Compatibility, pp. 265−270 (Denver, 2013).
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“Considerations of Quantum Key Distribution for Space
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Length Modulation in Semiconducting Carbon Nanotube
Field Effect Transistors,” IEEE Transactions on Nanotechnology, Vol. 13, No. 2, pp. 176−181 (2014).
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1E 2259+586 and AXP 4U 0142+61,” Astrophysical Journal, Vol. 772, No. 1, p. 11 (2013).
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1806-20 and SGR 1900+14,” Astrophysical Journal, Vol.
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Clocks in Space,” Proceedings of 2012 European Frequency
and Time Forum, pp. 501−508 (Gothenburg, Sweden,
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J. Camparo and G. Fathi, “The 2nd Harmonic Signal in
Vapor-Cell Clocks & Error-Signal Quality: Does S2
Imply dS1/dΔ?,” 2013 Joint European Frequency and Time
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J. Camparo, M. Huang, and T. Driskell, “The Influence of Laser Polarization Noise on the Short-Term Stability of CPT
Atomic Clocks,” 2013 Joint European Frequency and Time
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J. C. Camparo, F. Wang, Y. Chan, and W. E. Lybarger, “Oscillator Model for rf-Discharge Lamps Used in Atomic
Clocks: The rf-Discharge as a Complex Permeability
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Remote Sensing Symposium, pp. 1092−1095 (Munich,
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Band Sensor Data Records,” Proceedings of SPIE—The
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BOOKMARKS
“Single Event Transients Induced by Picosecond Pulsed
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Storms,” 2012 American Geophysical Union Fall Meeting
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M. Chen, C. L. Lemon, T. B. Guild, J. L. Roeder, et al., “Comparison of Self-Consistent Simulations with Observed
Magnetic Field and Ion Plasma Parameters in the Ring
Current during the 10 August 2000 Magnetic Storm,”
Journal of Geophysical Research-Space Physics, Vol. 117
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S. G. Claudepierre et al., “Kelvin-Helmholtz Instability of
the Magnetospheric Boundary in a Three-Dimensional
Global MHD Simulation during Northward IMF Conditions,” Journal of Geophysical Research-Space Physics, Vol.
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S. G. Claudepierre et al., “Prompt Energization of Relativistic and Highly Relativistic Electrons during a Substorm
Interval: Van Allen Probes Observations,” Geophysical
S. G. Claudepierre, J. F. Fennell, et al., “Discovery of the
Action of a Geophysical Synchrotron in the Earth’s Van
Allen Radiation Belts,” Nature Communications, Vol. 4
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J. H. Clemmons, et al., “Van Allen Probes Observation of
Localized Drift Resonance between Poloidal Mode UltraLow Frequency Waves and 60 keV Electrons,” Geophysical
J. Clemmons, J. Fennell, J. Blake, J. Roeder, S. Claudepierre,
H. Spence, and C. Kletzing, “Electron Microburst Physics
Using the Burst Support Mode on RBSP’s MagEIS Instrument,” 2012 American Geophysical Union Fall Meeting
J. H. Clemmons, R. W. Walterscheid, A. B. Christensen,
and R. L. Bishop, “Rapid, Highly Structured Meridional
Winds and Their Modulation by Non Migrating Tides:
Measurements from the Streak Mission,” Journal of
Geophysical Research: Space Physics, Vol. 118, No. 2, pp.
866−877 (2013).
J. G. Coffer, M. Huang, and J. C. Camparo, “Self-Pulsing in
Alkali rf-Discharge Lamps,” Proceedings of 2012 IEEE
International Frequency Control Symposium, pp. 687−691
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D. J. Coleman and K. T. Luey, “VUV Modification of Surfaces to Induce Film Formation,” Proceedings of SPIE—The
K. B. Crawford, D. L. Kim, R. J. Rudy, R. W. Russell, et al.,
“Evolution from Protoplanetary to Debris Discs: the
Transition Disc around HD 166191,” Monthly Notices
of the Royal Astronomical Society, Vol. 438, No. 4, pp.
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M. Crofton, J. Young, et al., “Further Results from the U.S.
Round-Robin Experiment on Plasma Expansion Speed,”
51st AIAA Aerospace Sciences Meeting including the New
Horizons Forum and Aerospace Exposition (Grapevine,
TX, 2013).
M. W. Crofton, J. C. Nocerino, J. A. Young, et al., “NEXT Ion
Engine Plume Deposition Rates: QCM Measurements,”
52nd AIAA Aerospace Sciences Meeting (National Harbor,
MD, 2013).
M. W. Crofton and J. E. Pollard, “Thrust Augmentation by
Charge Exchange,” 49th AIAA/ASME/SAE/ASEE Joint
Propulsion Conference (San Jose, 2013).
M. W. Crofton, J. A. Young, et al., “A U.S. Round-Robin
Experiment on Characteristics of Arc Plasma Expansion,”
4th AIAA Atmospheric and Space Environments Conference (New Orleans, 2012).
M. W. Crofton, J. A. Young, et al., “First Preliminary Results
from U.S. Round Robin Tests,” IEEE Transactions on
Plasma Science, Vol. 41, No. 12, pp. 3310−3322 (2013).
E. Deionno, D. C. Marvin, and S. H. Liu, “Assessment of AP9
and Solar Cell Degradation Models with Flight Data,”
2013 IEEE 39th Photovoltaic Specialists Conference, pp.
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E. Deionno, M. D. Looper, J. V. Osborn, et al., “Displacement
Damage in TiO₂ Memristor Devices,” IEEE Transactions
on Nuclear Science, Vol. 60, No. 2, pp. 1379−1383 (2013).
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Effects Studies on Thin Film TiO₂ Memristor Devices,”
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Visible Infrared Imaging Radiometer Suite Onboard the
Suomi National Polar-Orbiting Partnership (S-NPP)
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Visible Infrared Imaging Radiometer Suite (VIIRS) Rotating Telescope Assembly (RTA),” Proceedings of SPIE—The
J. D. Desain, T. J. Curtiss, J. K. Fuller, et al., “Test of Hybrid
Rocket Fuel Grains with Swirl Patterns Fabricated Using
Rapid Prototyping Technology,” 49th AIAA/ASME/SAE/
ASEE Joint Propulsion Conference (San Jose, 2013).
K. D. Diamant, R. Spektor, E. J. Beiting, J. A. Young, and
T. J. Curtiss, “The Effects of Background Pressure on Hall
Thruster Operation,” 48th AIAA/ASME/SAE/ASEE Joint
Propulsion Conference and Exhibit (Atlanta, 2012).
J. T. Dickey et al., “Professor Bud Peterson on His 60th Birthday,” International Journal of Heat and Mass Transfer, Vol.
58, No. 1-2, pp. 3−5 (2013).
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Reactivities of Carbides and Nitrides of Titanium and
Vanadium,” Coordination Chemistry Reviews, Vol. 257,
No. 1, pp. 93−109 (2013).
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Computable Bounds,” Advances in the Astronautical Sciences, pp. 2519−2537 (2012).
F. Di Teodoro et al., “SBS-Managed High-Peak-Power
Nanosecond-Pulse Fiber-Based Master Oscillator Power
Amplifier,” Optics Letters, Vol. 38, No. 13, pp. 2162−2164
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through Global Positioning System Metric Tracking,”
IEEE Aerospace Conference Proceedings (Big Sky, MT,
2013).
R. B. Dybdal, S. J. Curry, F. Lorenzelli, and D. J. Hinshilwood, “Multiple Polarization Communications,” IEEE
Antennas and Propagation Society, AP-S International
Symposium (Digest) (Chicago, 2012).
J. L. Emdee, “EELV Progress in Compliance with U.S. Space
Debris Mitigation Policies,” AIAA SPACE 2012 Conference
and Exposition (Pasadena, CA, 2012).
B. Etefia et al., “Supporting Military Communications with
Named Data Networking: An Emulation Analysis,”
Proceedings—IEEE Military Communications Conference
(Orlando, FL, 2012).
J. Feeley and I. Csiszar, “Product Maturity Status for the
SNPP Sensor and Environmental Data Records,” 93rd
American Meteorological Society Annual Meeting (Austin,
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J. Fennell, J. Blake, J. Clemmons, H. Spence, S. Claudepierre,
and J. Roeder, “Initial Look at the Electron Slot and Inner
Zone Regions with RBSP/MagEIS,” 2012 American Geophysical Union Fall Meeting (San Francisco, 2012).
J. Fennell, J. B. Blake, M. Looper, et al., “First Results from
CSSWE CubeSat: Characteristics of Relativistic Electrons
in the Near-Earth Environment during the October 2012
Magnetic Storms,” Journal of Geophysical Research-Space
Physics, Vol. 118, No. 10, pp. 6489−6499 (2013).
R. Fields, “Rapid Low Cost Electro-Optic Prototyping for
Space through Use of Cubesats,” Applied Industrial Optics:
Spectroscopy, Imaging, and Metrology (2012).
C. E. Foerster, V. Goyal, J. Rome, D. N. Patel, and G. L. Steckel, “Strength of Composite Foam Core Sandwich Structures Subjected to Thermomechanical Loading,” AIAA/
ASME/ASCE/AHS/ASC Structures, Structural Dynamics
and Materials Conference (Boston, 2013).
E. Fong and T. T. Lam, “Application of Solution Structure
Theorems for Asymmetric Heating in Thin Films,” 44th
AIAA Thermophysics Conference (San Diego, 2013).
E. Fong and T. T. Lam, “Asymmetrical Collision of Thermal
Waves in Thin Films: An Analytical Solution,” International Journal of Thermal Sciences, Vol. 77, pp. 55−65
(2014).
B. Foran, M. Brodie, et al., “Material Evidence for Multiple
Firings of Ancient Athenian Red-Figure Pottery,” Journal of the American Ceramic Society, Vol. 96, No. 7, pp.
2031−2035 (2013).
J. Fortune and R. Valerdi, “A Framework for Reusing Systems
Engineering Products,” Systems Engineering, Vol. 16, No.
3, pp. 304−312 (2013).
P. D. Fuqua, C. J. Panetta, J. D. Barrie, et al., “Out of Band
Scatter Measurements from OLI Optical Bandpass Filters,” Proceedings of SPIE—The International Society for
Optical Engineering (2012).
C. M. Gee, G. Sefler, P. T. S. Devore, and G. C. Valley, “Spurious-Free Dynamic Range of a High-Resolution Photonic Time-Stretch Analog-to-Digital Converter System,”
Microwave and Optical Technology Letters, Vol. 54, No. 11,
pp. 2558−2563 (2012).
J. Geis, C. Florio, D. Moyer, K. Rausch, and F. De Luccia,
“VIIRS Day-Night Band Gain and Offset Determination
and Performance,” Proceedings of SPIE—The International
Society for Optical Engineering (2012).
L. Gelinas, J. Hecht, R. Walterscheid, I. Reid, and J. Woithe,
“Sources and Ducting of Gravity Waves Observed at
Adelaide and Alice Springs,” 2012 American Geophysical
Union Fall Meeting (San Francisco, 2012).
L. J. Gelinas, R. L. Walterschied, et al., “Observations of an
Inertial Peak in the Intrinsic Wind Spectrum Shifted by
Rotation in the Antarctic Vortex,” Journal of the Atmospheric Sciences, Vol. 69, No. 12, pp. 3800−3811 (2012).
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Burnout Observed in Schottky Diodes,” IEEE Radiation
Effects Data Workshop (San Francisco, 2013).
E. Ghashghai and J. Hamilton, “Net-Centric Network and
Operational Management,” AIAA SPACE Conference and
Exposition (Pasadena, CA, 2012).
R. Gong, M. Broder, L. Jocic, and J. Gee, “Space Architecture
BOOKMARKS
Transition with Hosted Payloads,” AIAA SPACE Conference and Exposition (Pasadena, CA, 2012).
V. K. Goyal and J. I. Rome, “Analysis Methodology for
Assessing Delaminations in Composite Overwrapped
Pressure Vessels,” 53rd AIAA/ASME/ASCE/AHS/ASC
Structures, Structural Dynamics and Materials Conference
(Honolulu, 2012).
V. K. Goyal, J. I. Rome, P. M. Schubel, D. N. Patel, and G. L.
Steckel, “Predicting and Measuring the Strength Reduction of Sandwich Structures with Spliced Foam Cores,”
53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural
Dynamics and Materials Conference (Honolulu, 2012).
T. P. Graves, P. Hanson, J. M. Michaelson, A. D. Farkas, and
A. A. Hubble, “Fast Shutdown Protection System for
Radio Frequency Breakdown and Multipactor Testing,”
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S. Guarro, “On the Estimation of Space Launch Vehicle Reliability,” International Journal of Performability Engineering, Vol. 9, No. 6, pp. 619−631 (2013).
S. Guarro, “Risk Assessment of New Space Launch and
Supply Vehicles,” 11th International Probabilistic Safety
Assessment and Management Conference and the Annual European Safety and Reliability Conference, pp.
5157−5164 (2012).
T. Guild, P. O’Brien, and M. Looper, “Inner Radiation Belt
Dynamics and Climatology,” 2012 American Geophysical
Union Fall Meeting (San Francisco, 2012).
M. E. Harmon, J. Schuetz, et al., “The Microstructure of
Collagen Type I Gel Cross-Linked with Gold Nanoparticles,” Colloids and Surfaces B: Biointerfaces, Vol. 101, pp.
118−125 (2013).
J. H. Hecht, P. R. Straus, et al., “An Empirical Determination
of Proton Auroral Far Ultraviolet Emission Efficiencies
Using a New Nonclimatological Proton Flux Extrapolation Method,” Journal of Geophysical Research—Space
Physics, Vol. 117 (2012).
M. Hecht, J. Tamaki, and D. Lo, “Modeling of Failure Detection and Recovery in SysML,” 2013 IEEE International
Symposium on Software Reliability Engineering Workshops,
pp. 85−95 (Pasadena, CA, 2013).
J. M. Helt, “High Vacuum Tribometry Tests of Fluid Lubricants on Bearing Steels,” ACS National Meeting Book of
Abstracts (San Diego, 2012).
H. Helvajian et al., “Welding Characteristics of Foturan
Glass Using Ultrashort Laser Pulses,” 31st International
Congress on Applications of Lasers and Electro-Optics, pp.
775−783 (Anaheim, CA, 2012).
J. Hicks, “Fast, Blind, and Joint Maximum Likelihood Estimation of MPSK Signal Parameters,” IEEE International
Conference on Communications, pp. 3476−3481 (Ottawa,
Canada, 2012).
A. C. Hoheb, “System Engineering Competencies for Space
System Program Managers,” AIAA SPACE 2013 Conference and Exposition (San Diego, 2013).
F. R. Hoots, “Satellite Catalog Renumbering: What Does
That Mean and Should I Be Worried,” National Technical
Information Service (2013).
D. Houston, D. Buettner, and M. Hecht, “Defectivity Profiling with Dynamic COQUALMO: An Explication and
Product Quality Retrospective,” Journal of Software: Evolution and Process, Vol. 24, No. 7, pp. 803−814 (2012).
D. X. Houston and D. J. Buettner, “Modeling User Story
Completion of an Agile Software Process,” ACM International Conference Proceeding Series, pp. 88−97 (2013).
M. Huang, T. U. Driskell, and J. C. Camparo, “Coherent
Population Trapping and Polarization Fluctuations: The
Independent-Modulator Approximation for CoherentPopulation-Trapping Line Shapes,” Physical Review A,
Vol. 87, No. 5 (2013).
P. Ionov, “Spectral Response of Fiber-Coupled Fabry-Perot
Etalons,” Journal of the Optical Society of America, Vol. 31,
No. 3, pp. 505−509 (2014).
B. C. Jacquot et al., “Atomically Precise Surface Engineering
of Silicon CCDs for Enhanced UV Quantum Efficiency,”
Journal of Vacuum Science and Technology A: Vacuum,
Surfaces and Films, Vol. 31, No. 1 (2013).
A. B. Jenkin, J. McVey, and B. D. Howard, “Uncertainty in
Lifetime of Highly Eccentric Transfer Orbits Due to Solar
Resonances,” Advances in the Astronautical Sciences, pp.
3041−3057 (2012).
A. B. Jenkin, J. P. McVey, and G. E. Peterson, “ISS Protection
Process for the COLA Gap after Launch,” AIAA SPACE
Conference and Exposition (2012).
A. B. Jenkin, M. E. Sorge, G. E. Peterson, J. P. McVey, and
B. B. Yoo, “100-Year Low Earth Orbit Debris Population Model,” Advances in the Astronautical Sciences, pp.
139−157 (2012).
C. Jo-Chieh, C. Sunshine, et al., “Protected MILSATCOM
Design for Affordability Risk Reduction (DFARR),” 2013
IEEE Military Communications Conference, pp. 998−1001
(San Diego, 2013).
A. M. Kabe and E. Perl, “Limitations of Base Shake Analysis
and Testing of Flight Configured Spacecraft,” European
Space Agency (2012).
R. Khullar et al., “Advanced Extremely High Frequency
Mission Planning: Will Its Legacy Dictate Its Future?,”
Proceedings—2012 IEEE 1st AESS European Conference
on Satellite Telecommunications (Rome, 2012).
Y. Kim and H. Helvajian, “Local Modification of Speed of
Sound in Lithium Alumino-Silicate Glass/Ceramic Mate-
rial by Pulsed Laser Irradiation and Thermal Processing,” Journal of Physical Chemistry, Vol. 117, No. 46, pp.
11954−11962 (2013).
K. W. Kloster et al., “Preliminary Analysis of Ballistic Trajectories to Uranus Using Gravity-Assists from Venus, Earth,
Mars, Jupiter, and Saturn,” Advances in the Astronautical
Sciences, pp. 3411−3428 (2012).
R. Koga et al., “The Single Event Revolution,” IEEE Transactions on Nuclear Science, Vol. 60, No. 3, pp. 1824−1835
(2013).
R. Koga, C. Paul, D. Romeo, V. Petrosyan, and J. George,
“Single Event Effects Sensitivity of 180 and 350 nm SiGe
HBT Microcircuits,” 2013 IEEE Radiation Effects Data
Workshop (San Francisco, 2013).
R. Kohli et al., “Decision Gate Process for Assessment of a
NASA Technology Development Portfolio,” AIAA SPACE
S. Kohn et al., “Commentary: JWST Near-Infrared Detector
Degradation—Finding the Problem, Fixing the Problem,
and Moving Forward,” AIP Advances, Vol. 2, No. 2 (2012).
T. Kopp et al., “First-Light Imagery from Suomi NPP VIIRS,”
Bulletin of the American Meteorological Society, Vol. 94,
No. 7, pp. 1019−1029 (2013).
J. Kreng et al., “EELV Incorporates GPS Metric Tracking as a
Range Tracking Source,” Proceedings of the International
Telemetering Conference (San Diego, 2012).
D. Kunkee et al., “Foreword to the Special Issue on Radio
Frequency Interference: Identification, Mitigation, and
Impact Assessment,” IEEE Transactions on Geoscience and
Remote Sensing, Vol. 51, No. 10, pp. 4915−4917 (2013).
S. D. La Lumondiere, Y. Sin, W. T. Lotshaw, S. C. Moss, et
al., “Characteristics of Bulk InGaAsSbN/GaAs Grown by
Metalorganic Vapor Phase Epitaxy (MOVPE),” Journal of
Crystal Growth, Vol. 370, pp. 163−167 (2013).
T. T. Lam, “A Generalized Heat Conduction Solution for
Ultrafast Laser Heating in Metallic Films,” International
Journal of Heat and Mass Transfer, Vol. 73, pp. 330−339
(2014).
T. T. Lam, “A Unified Solution of Several Heat Conduction
Models,” International Journal of Heat and Mass Transfer,
Vol. 56, No. 1-2, pp. 653−666 (2013).
T. T. Lam and E. Fong, “Application of Solution Structure
Theorems to Cattaneo-Vernotte Heat Conduction Equation with Non-Homogeneous Boundary Conditions,”
Heat and Mass Transfer, Vol. 49, No. 4, pp. 509−519
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J. R. Lince, A. M. Pluntze, S. A. Jackson, G. Radhakrishnan,
and P. M. Adams, “Tribochemistry of MoS₃ Nanoparticle
Coatings,” Tribology Letters, Vol. 53, No. 3, pp. 543−554
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D. Liu, S. V. Didziulis, and J. D. Fowler, “Assessment of
Particle Deposition Inside Payload Fairing from Launch
Vehicle Plume Contribution,” Proceedings of SPIE—The
M. D. Looper et al., “LEEM: A New Empirical Model of
Radiation-Belt Electrons in the Low-Earth-Orbit Region,”
Journal of Geophysical Research—Space Physics, Vol. 117
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M. D. Looper et al., “Relative Contributions of Galactic Cosmic Rays and Lunar Proton ‘Albedo’ to Dose and Dose
Rates near the Moon,” Space Weather—The International
Journal of Research and Applications, Vol. 11, No. 11, pp.
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M. D. Looper, J. E. Mazur, et al., “Energy Spectra, Composition, and Other Properties of Ground-Level Events during Solar Cycle 23,” Space Science Reviews, Vol. 171, No.
1-4, pp. 97−120 (2012).
M. D. Looper, J. E. Mazur, J. B. Blake, et al., “The Deep Space
Galactic Cosmic Ray Lineal Energy Spectrum at Solar
Minimum,” Space Weather, Vol. 11, No. 6, pp. 361−368
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M. D. Looper, J. E. Mazur, J. B. Blake, et al., “The Radiation
Environment near the Lunar Surface: CRaTER Observations and Geant4 Simulations,” Space Weather, Vol. 11,
No. 4, pp. 142−152 (2013).
W. T. Lotshaw, S. D. La Lumondiere, et al., “Investigation of
Carrier Removal from QD TJSCs,” Proceedings of SPIE—
The International Society for Optical Engineering (2013).
E. C. Lundgren et al., “Design and Maintainability Considerations regarding the Effects of Suborbital Flights on Composite Constructed Vehicles,” 53rd AIAA/ASME/ASCE/
AHS/ASC Structures, Structural Dynamics and Materials
Conference (Honolulu, 2012).
D. K. Lynch, R. J. Rudy, R. W. Russell, et al., “The Expanding
Dusty Bipolar Nebula around the Nova V1280 Scorpi,”
Astronomy and Astrophysics, Vol. 545 (2012).
S. Maghsoudy-Louyeh et al., “Subsurface Image Analysis of
Plant Cell Wall with Atomic Force Microscopy,” Journal of
Advanced Microscopy Research, Vol. 8, No. 2, pp. 100−104
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V. N. Mahajan, “Aberration Balancing, Orthonormal Polynomials, and Wavefront Analysis,” Frontiers in Optics (2012).
V. N. Mahajan, “Study of Zernike Polynomials of an Elliptical Aperture Obscured with an Elliptical Obscuration:
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V. N. Mahajan et al., “Imaging by a System with a Hexagonal Pupil,” Applied Optics, Vol. 52, No. 21, pp. 5112−5122
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V. N. Mahajan et al., “Imaging Characteristics of Zernike and
BOOKMARKS
Annular Polynomial Aberrations,” Applied Optics, Vol. 52,
No. 10, pp. 2062−2074 (2013).
V. N. Mahajan et al., “Orthonormal Aberration Polynomials
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E. M. Mahr and R. E. Bitten, “Evaluating Options for Enhancing Technology Development and Controlling Cost
Growth,” International Geoscience and Remote Sensing
Symposium, pp. 5654−5657 (Munich, Germany, 2012).
N. Marechal, R. Dickinson, and G. Karmyan, “A 2D Wavenumber Domain Phase Model for Ground Moving
Vehicles in Synthetic Aperture Radar Imagery,” Inverse
Problems, Vol. 29, No. 5 (2013).
N. J. Marechal, S. S. Osofsky, and R. M. Bloom, “Demonstration of W-Band SAR Imagery with a Ground-Based
System Having 7.5 GHz of Bandwidth Obtained with
a Stepped Chirp Waveform,” IEEE Transactions on
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Improvements and Application to the NASA/DARPA
Manned Geosynchronous Servicing Study,” AIAA SPACE
A. Matache and E. L. Valles, “Performance of Decoder-Based
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J. F. McNeill, E. L. Chapman, and M. E. Sklar, “Under42 CROSSLINK FALL 2014
standing Cost Growth during Operations of Planetary
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J. P. McVey and C. Chao, “Automated Ballistic Coefficient
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N. Melamed, “Development of a Handbook and an Online
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A. W. Merrill, M. A. Clark, J. Hoffman, G. L. Gallien, and
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Bands Calibration Algorithm and On-Orbit Performance,” Proceedings of SPIE - The International Society for
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E. J. Nemanick, “Electrochemistry of Lithium-Oxygen Batteries Using Microelectrode Voltammetry,” Journal of
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G. E. Peterson, “Effect of Future Space Debris on Mission
Utility and Launch Accessibility,” Advances in the Astronautical Sciences, pp. 201−215 (2012).
E. J. Nemanick and R. P. Hickey, “The Effects of O₂ Pressure on Li-O₂ Secondary Battery Discharge Capacity and
Rate Capability,” Journal of Power Sources, Vol. 252, pp.
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R. G. Pettit and N. Mezcciani, “Highlighting the Challenges
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Systems,” ICSE Workshop on Software Engineering for
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D. Nigg and J. Evans, “Developing Rapid Tradespace
Exploration Trends through Multidisciplinary Design
Optimization,” AIAA SPACE Conference and Exposition
A. L. Polite-Wilson, “Ensuring Competency Optimization
from a Systems Thinking Perspective,” AIAA SPACE 2013
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T. P. O’Brien, “Breaking All the Invariants: Anomalous Electron Radiation Belt Diffusion by Pitch Angle Scattering in
the Presence of Split Magnetic Drift Shells,” Geophysical
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K. Rausch, F. De Luccia, D. Moyer, J. Cardema, et al.,
BOOKMARKS
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K. Rausch, S. Houchin, J. Cardema, G. Moy, E. Haas, and F. J.
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Polar Orbiting Partnership (S-NPP) Visible Infrared Imaging Radiometer Suite (VIIRS) Reflective Solar Bands,”
Journal of Geophysical Research—Atmospheres, Vol. 118,
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S. A. Reed et al., “High-Intensity Laser-Driven Proton Acceleration Enhancement from Hydrogen Containing
Ultrathin Targets,” Applied Physics Letters, Vol. 103, No.
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D. F. Rock, “Using Differential Ray Tracing in Stray Light
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J. I. Rome, V. K. Goyal, et al., “Specimen Size and Effective
Compressive Stiffness of 3d Fiber Reinforced Foam Core
Sandwich Structures,” 28th Annual Technical Conference
of the American Society for Composites, pp. 1325−1334
(State College, PA, 2013).
J. I. Rome, V. K. Goyal, P. Schubel, G. Steckel, D. Patel, Y.
Kim, et al., “Modeling Failure of 3D Fiber Reinforced
Foam Core Sandwich Structures with Defects,” 53rd
AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference (Honolulu, 2012).
J. I. Rome, V. K. Goyal, P. M. Schubel, D. N. Patel, and G. L.
Steckel, “Identification of Failure Mechanisms in Sandwich Structures with Foam Core Thickness Mismatches,”
53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural
Dynamics and Materials Conference (Honolulu, 2012).
G. Rosene et al., “A Model to Estimate Separator Forces
during Ball Speed Variations,” ASTM Special Technical
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R. Russell et al., “Spiral Arms in the Asymmetrically Illuminated Disk of MWC 758 and Constraints on Giant Planets,” Astrophysical Journal, Vol. 762, No. 1, p. 13 (2013).
R. W. Russell et al., “High-Resolution Near-Infrared Polarimetry of a Circumstellar Disk Around UX Tau A,”
Publications of the Astronomical Society of Japan, Vol. 64,
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R. W. Russell et al., “Imaging the Disk and Jet of the Classical
T Tauri Star AA Tau,” Astrophysical Journal, Vol. 762, No.
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Photometric Variability: The Herbig Ae Star HD 163296,”
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R. W. Russell, R. J. Rudy, D. J. Gutierrez, D. L. Kim, K. Crawford, et al., “Further Analysis of Infrared Spectrophotometric Observations of High Area to Mass Ratio (HAMR)
Objects in GEO,” Acta Astronautica, Vol. 80, pp. 154−165
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P. M. Schubel et al., “Response and Damage Tolerance of
Composite Sandwich Structures under Low Velocity Impact,” Proceedings of the Society for Experimental Mechanics, Vol. 52, No. 1, pp. 37−47 (2012).
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and Control of Multiscale Dynamical Systems,” Earth and
Space 2012—Proceedings of the 13th ASCE Aerospace Division Conference and the 5th NASA/ASCE Workshop on
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G. A. Sefler and G. C. Valley, “Mitigation of Group-DelayRipple Distortions for Use of Chirped Fiber-Bragg Gratings in Photonic Time-Stretch ADCs,” Journal of Lightwave Technology, Vol. 31, No. 7, pp. 1093−1100 (2013).
S. S. Shen and K. A. Roettiger, “Detection of Abandoned
Mines/Caves Using Airborne LWIR Hyperspectral Data,”
Proceedings of SPIE—The International Society for Optical
Engineering (2012).
Y. Sin, B. Foran, N. Presser, S. La Lumondiere, W. Lotshaw,
and S. C. Moss, “Traps and Defects in Pre- and PostProton Irradiated AlGaN-GaN High Electron Mobility
Transistors and AlGaN Schottky Diodes,” Proceedings of
(2013).
Y. Sin, N. Presser, S. La Lumondiere, N. Ives, W. Lotshaw,
and S. C. Moss, “Catastrophic Optical Bulk Damage
(COBD): A New Degradation Mode in High Power
InGaAs-AlGaAs Strained QW Lasers,” Conference Digest—IEEE International Semiconductor Laser Conference,
pp. 116−117 (San Diego, 2012).
Y. Sin, S. La Lumondiere, B. Foran, N. Ives, N. Presser, W.
Lotshaw, and S. C. Moss, “Catastrophic Degradation in
High Power InGaAs-AlGaAs Strained Quantum Well
Lasers and InAs-GaAs Quantum Dot Lasers,” Proceedings
of SPIE—The International Society for Optical Engineering
(2013).
Y. Sin, S. La Lumondiere, B. Foran, W. Lotshaw, and S. C.
Moss, “Catastrophic Optical Bulk Damage (COBD)
Processes in Aged and Proton-Irradiated High Power
InGaAs-AlGaAs Strained Quantum Well Lasers,” Proceedings of SPIE—The International Society for Optical
Engineering (2013).
Y. Sin, S. La Lumondiere, B. Foran, W. Lotshaw, S. C. Moss,
et al., “Carrier Dynamics and Defects in Bulk 1eV InGaAsNSb Materials and InGaAs Layers with MBL Grown
by MOVPE for Multi-Junction Solar Cells,” Materials
Research Society Symposium Proceedings, pp. 245−251
Y. Sin, S. La Lumondiere, W. Lotshaw, S. C. Moss, et al.,
“Carrier Dynamics in Bulk 1eV InGaAsNSb Materials
and Epitaxial Lift Off GaAs-InAlGaP Layers Grown by
MOVPE for Multi-Junction Solar Cells,” Proceedings of
(2013).
K. Siri, “Group Maximum Power Tracking for Distributed
Power Sources,” 11th International Energy Conversion
Engineering Conference (San Jose, 2013).
P. Smith, M. Ferringer, R. Kelly, and I. Min, “Budget-Constrained Portfolio Trades Using Multiobjective Optimization,” Systems Engineering, Vol. 15, No. 4, pp. 461−470
(2012).
Turret via Pressure-Sensitive Paint,” 44th AIAA Plasmadynamics and Lasers Conference (San Diego, 2013).
J. Thordahl et al., “The Comparison of Unsteady Pressure
Field over Flat- and Conformal-Window Turrets Using
Pressure Sensitive Paint,” 44th AIAA Plasmadynamics and
Lasers Conference (San Diego, 2013).
J. Thordahl et al., “The Estimation of the Unsteady Aerodynamic Force Applied to a Turret in Flight,” 44th AIAA
Plasmadynamics and Lasers Conference (San Diego, 2013).
M. M. Tong, “Inverse Mass Matrix Factorization Using Momentum Equations of a Rigid Multibody System,” AIAA
Guidance, Navigation, and Control Conference (Minneapolis, 2012).
M. E. Sorge et al., “Rapid Orbital Characterization of Local
Area Space Objects Utilizing Image-Differencing Techniques,” Proceedings of SPIE—The International Society for
D. Tratt, K. Buckland, S. Young, D. Riley, and I. Leifer,
“Source Attribution of Methane Emission from Petroleum Production Operations Using High-Resolution
Airborne Thermal-Infrared Imaging Spectrometry,” 2012
American Geophysical Union Fall Meeting (San Francisco,
2012).
M. E. Sorge et al., “Sensor Model for Space-Based Local Area
Sensing of Debris,” Proceedings of SPIE—The International
Society for Optical Engineering (2013).
D. M. Tratt, “Remote Sensing Atmospheric Trace Gases with
Infrared Imaging Spectroscopy,” Eos, Transactions American Geophysical Union, Vol. 93, No. 50, p. 525 (2012).
J. R. Srour and J. W. Palko, “Displacement Damage Effects in
Irradiated Semiconductor Devices,” IEEE Transactions on
Nuclear Science, Vol. 60, No. 3, pp. 1740−1766 (2013).
D. M. Tratt, K. N. Buckland, S. J. Young, P. D. Johnson, et
al., “Remote Sensing Visualization and Quantification
of Ammonia Emission from an Inland Seabird Colony,”
Journal of Applied Remote Sensing, Vol. 7, No. 1 (2013).
D. W. Stephens and P. Broussinos, “Rideshare on EELV Using ESPA—Challenges and Opportunities,” AIAA SPACE
A. G. Sun, M. W. Crofton, J. A. Young, W. A. Cox, and
E. J. Beiting, “L-, S-, and C-Band EMI Measurement and
Characterization of Spacecraft ESD Events,” IEEE Transactions on Plasma Science, Vol. 41, No. 12, pp. 3505−3511
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Y. R. Takeuchi, S. E. Davis, and M. A. Eby, “Steel and Hybrid
Spacecraft Ball-Bearing Thermal Conductance Comparisons,” ASTM Special Technical Publication, pp. 118−142
(2012).
Y. R. Takeuchi, S. E. Davis, M. A. Eby, J. K. Fuller, D. L.
Taylor, and M. J. Rosado, “Bearing Thermal Conductance
Measurement Test Method and Experimental Design,”
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D. P. Taylor, W. W. Hansen, L. Steffeney, and C. Chu, “Micromachined Reference Samples for Particle Counting,”
Proceedings of SPIE—The International Society for Optical
Engineering (2012).
F. D. Teodoro, “High-Power Fiber Laser Sources for Remote
Sensing,” Proceedings of SPIE—The International Society
J. Thordahl et al., “Study of Unsteady Surface Pressure on a
C. Tschan et al., “Advancing Intelligent Systems in the Aerospace Domain,” AIAA Infotech at Aerospace Conference
(Boston, 2013).
C. Tschan et al., “Creating a Comprehensive Feature Space
Library for Machine Learning,” AIAA Infotech at Aerospace Conference and Exhibit (Garden Grove, CA, 2012).
C. Tschan et al., “How Intelligent Is Your Satellite or Ground
System?,” AIAA SPACE 2013 Conference and Exposition
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G. C. Valley, G. A. Sefler, and T. J. Shaw, “Compressive Sensing of Sparse Radio Frequency Signals Using Optical
Mixing,” Optics Letters, Vol. 37, No. 22, pp. 4675−4677
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G. C. Valley, G. A. Sefler, and T. J. Shaw, “Sensing RF Signals
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A. Vore et al., “High Lift Flap System for a Tailless Transport
Aircraft,” 51st AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition
(Grapevine, TX, 2013).
D. Walker, L. De-Ling, and S. H. Liu, “Increasing the
Limiting Efficiency of Space Solar Cells at End-of-Life,”
BOOKMARKS
2013 IEEE 39th Photovoltaic Specialists Conference, pp.
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R. L. Walterscheid, “The Propagation of Transient Wave
Packets in Highly Dissipative Media,” Journal of Geophysical Research—Space Physics, Vol. 118, No. 2, pp. 878−884
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R. Walterscheid et al., “Angular Momentum Budget in General Circulation Models of Superrotating Atmospheres:
A Critical Diagnostic,” Journal of Geophysical Research—
Planets, Vol. 117 (2012).
R. L. Walterscheid et al., “Wave Heating and Jeans Escape
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R. L. Walterscheid, L. J. Gelinas, J. H. Hecht, et al., “Instability Structures during Periods of Large Richardson Number
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R. L. Walterscheid, J. H. Hecht, L. J. Gelinas, et al., “An Intense Traveling Airglow Front in the Upper MesosphereLower Thermosphere with Characteristics of a Bore
Observed over Alice Springs, Australia, during a Strong
2 Day Wave Episode,” Journal of Geophysical Research D:
Atmospheres, Vol. 117, No. 22 (2012).
M. A. Weaver and W. H. Ailor, “Reentry Breakup Recorder:
Concept, Testing, Moving Forward,” AIAA SPACE Conference and Exposition (Pasadena, CA, 2012).
B. H. Weiller et al., “Graphene MEMS: AFM Probe Performance Improvement,” ACS Nano, Vol. 7, No. 5, pp.
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B. H. Weiller et al., “Vertical Graphene-Based Hot-Electron
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J. W. Welch, “Considerations in Assessing Risk for Tailoring
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International Conference on Environmental Systems (San
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N. P. Wells, S. D. La Lumondiere, Y. Sin, W. T. Lotshaw, S. C.
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Epitaxy,” Applied Physics Letters, Vol. 104, No. 5 (2014).
M. J. Wenkel et al., “FORMOSAT-7/COSMIC-2 GNSS Radio
Occultation Constellation Mission for Global Weather
Monitoring,” IEEE Aerospace Conference Proceedings (Big
Sky, MT, 2013).
L. A. Wickman, “Comparing Crew Operations in Extreme
Environments: Arctic Shipping vs. Outer Space,” International Conference and Exhibition on Performance of Ships
and Structures in Ice, pp. 339−344 (Banff, Canada, 2012).
B. Y. Williams et al., “The Effect of Systematic Error in
Forced Oscillation Testing,” 50th AIAA Aerospace Sciences
Meeting Including the New Horizons Forum and Aerospace
Exposition (Nashville, 2012).
D. B. Witkin, “Influence of Microstructure on Mechanical
Behavior of Bi-Containing Pb-Free Solders,” IPC APEX
EXPO Conference and Exhibition, pp. 540−560 (San
Diego, 2013).
D. B. Witkin and I. A. Palusinski, “Influence of Low-Earth
Orbit Exposure on the Mechanical Properties of Silicon
Carbide,” Proceedings of SPIE—The International Society
D. R. Wood, “Analysis of Technology Transfer within Satellite Programs in Developing Countries Using Systems
Architecture,” AIAA SPACE 2013 Conference and Exposition (San Diego, 2013).
S. Yi, J. L. Hall, and B. P. Kasper, “Analysis, Testing, and
Operation of the MAGI Thermal Control System,” AIP
Conference Proceedings, pp. 1291−1298 (2014).
J. Yoshida, M. Cowdin, T. Mize, R. Kellogg, and D. Bearden,
“Complexity Analysis of the Cost Effectiveness of PI-Led
NASA Science Missions,” IEEE Aerospace Conference
Proceedings (2013).
J. A. Young, M. W. Crofton, et al., “Annular Engine Development Status,” 49th AIAA/ASME/SAE/ASEE Joint Propulsion Conference (San Jose, 2013).
J. A. Young, M. W. Crofton, et al., “Expanded Throttling Capabilities of the NEXT Thruster,” 49th AIAA/ASME/SAE/
ASEE Joint Propulsion Conference (San Jose, 2013).
J. A. Young, M. W. Crofton, W. Cox, D. C. Ferguson, R. C.
Hoffmann, A. T. Wheelock, et al., “Measurement of ESD
Plasma Propagation on a Positively Charged ISS Solar
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J. A. Young, M. W. Crofton, W. A. Cox, and J. S. Tran,
“Measurement of ESD Plasma Propagation on a Positively
Charged Ring Coupon,” Digest of Technical Papers—IEEE
International Pulsed Power Conference (San Francisco,
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J. A. Young, M. W. Crofton, K. D. Diamant, et al., “Plume
Characterization of the NEXT Thruster under Extended
Throttle Conditions,” 49th AIAA/ASME/SAE/ASEE Joint
Propulsion Conference (San Jose, 2013).
R. J. Zaldivar, J. P. Nokes, and H. I. Kim, “The Effect of
Surface Treatment on Graphite Nanoplatelets Used in
Fiber Reinforced Composites,” Journal of Applied Polymer
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Patents _________________________________
N. W. Schulenburg, D. W. Warren, D. J. Rudy, M. G. Martino,
M. A. Chatelain, and M. A. Rocha, “Nadir Emissive Hyperspectral Measurement Operation (NEHMO),” U.S. Patent
No. 8,304,730, November 2012
A sensor system has been developed that enables high
spectral and spatial resolution emissive hyperspectral imaging data to be collected in the laboratory. A test article of interest is placed under the sensor system, which is physically
translated over the test article while collecting hyperspectral data. The test article can be an opaque material (e.g.,
sand, concrete, a human) or a transmissive material (e.g.,
clothing, vegetation). This laboratory sensor capability uses
Aerospace’s Spatially Enhanced Broadband Array Spectrograph System (SEBASS) to collect spectral-spatial data in
the midwave infrared (2.5–5.5 micron) and the long-wave
infrared (7.5–13.5 micron) regions. Two spatial dimensions
of data are collected by physically translating a wide array
detector in a direction perpendicular to the width of the array. External optics are mounted to the SEBASS aperture to
change the focus of the instrument to a distance of 1 meter
from the sensor. National Institute of Standards and Technology–traceable thermal sources are used for calibrating
the SEBASS instrument. A test article is either heated or
illuminated using controlled thermal sources.
T. J. Grycewicz, “Methods for Estimating Peak Location on a
Sampled Surface with Improved Accuracy and Applications
to Image Correlation and Registration,” U.S. Patent No.
8,306,274, November 2012
Two methods commonly used to estimate the interpixel location of the peak value on a curve or surface are centroiding and curve fitting. In centroiding, a weighted average of
the sample values near the peak location is used to find the
center of mass of the peak. In curve fitting, the data points
near the peak are approximated by a mathematical curve or
surface with a known center point. These methods are subject to inaccuracies for a number of reasons. Chief among
them are that the data are noisy; a limited number of points
are used for the estimate; and the real-world signal is not
a perfect match to the mathematical surface used for fitting. In this invention, methods and systems for estimating peak location on a sampled surface (e.g., a correlation
surface generated from pixelated images) use one or more
processing techniques to determine multiple peak location
estimates for at least one sampled data set at a resolution
smaller than the spacing of the data elements. Estimates
selected from the multiple peak location estimates are then
combined to provide one or more refined estimates. In the
example of embodiments, multiple refined estimates are
combined to provide an estimate of overall displacement
(e.g., of an image or other sampled data representation of
an object).
D. A. Ksienski, W. L. Bloss, E. K. Hall, and J. P. McKay, “Heptagonal Antenna Array,” U.S. Patent No. 8,314,748, November 2012
It is ideal to provide an optimal packing density antenna
array with good sidelobe rejection when both mechanical
and electrical steering are at the same offsets. However, current antenna arrays only offer modest sidelobe rejection.
This invention is directed to a heptagonal antenna array
offering improved sidelobe rejection. For reasons not yet
fully understood, an unexpected and surprising discovery
was made that an eight-element array, having one center
element and seven exterior elements circumferentially surrounding the center element, has superior sidelobe rejection performance, even with an increase in interelemental
spacing. That is, sidelobe rejection is improved, surprisingly, in both the near and far sidelobes, yet the packing
density has been modestly degraded over the hexagonal
configuration. The system uses a heptagonal arrangement
in an eight-element array. The suppression of the sidelobes
relative to peak gain of the main beam has been improved
to –15 decibels.
J. A. Conway, J. V. Osborn, and R. A. Stevenson, “Plasmon Stabilized Laser Diodes,” U.S. Patent No. 8,325,776, December
2012
The conventional high-power laser diode does not fill its
laser gain cavity during standard operation. Instead, the
optical mode forms a filament from the optical and gain
dynamics of the device. The position of this lasing filament
is not static but rather moves through the device, creating
multimodal hot spots and thermal lenses that accelerate
failure of the device. This invention is directed to a large
area laser having a plasmonic reflector. The plasmonic reflector redistributes the lateral mode profile within the laser
diode to advantageously reduce the potential for filamented
or confined lasing and the consequential hot spots within
the laser diode. The plasmonic reflector serves to control
the diffusion of the optical field by redistribution, as being
diametrically opposed to the focusing, for mode spoilage,
mode expansion, or all of these. The reflector is preferably
a patterned metal film disposed in a multitransverse-mode
laser diode for redistributing the reflected light for controlling spatial, polarization, and spectral parameters of the
laser light. The reflector is used for generating free-space
laser exit beams by expanding, shaping, or manipulating
the laser light within the laser diode.
S. W. Janson, “Propulsion Systems and Methods Utilizing
Smart Propellant,” U.S. Patent No. 8,336,826, December
2012
Rocket propulsion is based on the high-speed ejection
of propellant mass. Conventional propellant mass, once
ejected, does not return, and available propellant mass
decreases with each propulsive maneuver. This invention
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is based on the ejection of “smart propellant devices,” individual propellant masses that can fine-tune their trajectory
after ejection at specific velocities to return to the spacecraft
for reuse. In many cases, such as orbit rephasing maneuvers, the returning smart propellant provides an additional
beneficial impulse. Smart propellant is composed of individual small spacecraft (e.g., pico- or nanospacecraft)
with navigation determination, attitude determination and
control, and propulsion systems. In example embodiments
in which the ejected smart propellant device returns to the
spacecraft and is recaptured, the smart propellant device,
less any onboard propellant mass expended for trajectory
modification, can be reused again and again. This enables
new space mission capabilities such as reuseable lunar
landers.
K. Siri, “Current Sharing Power System,” U.S. Patent No.
8,351,229, January 2013
Isolated ac-to-dc power systems with active power factor correction have been used in several applications for
drawing sinusoidal currents from utility grids or input ac
power sources, and regulation of dc output voltages being
isolated from the grid or the input power sources. Without active current sharing, parallel connection of these
identical power systems, respectively at their ac inputs and
dc outputs, is not feasible as a result of nonuniform current sharing among the paralleled power channels. When
parallel-connected, only one or a few power channels
have a dominant power contribution while the remaining
power channels are idle or make small contributions to the
common output load. In many cases, the oversubscribed
power channels have increased unreliability and shortened lifetimes from persistent thermal overstresses. This
invention includes multiple channels, and each channel
has a current-sharing controller that is coupled to a shared
current signal bus and a shared voltage signal bus. As a
consequence of multiple current-sharing controllers with
the two commonly shared buses, multiple power channels
of an ac-to-dc converter power system with active power
factor correction can be parallel connected to achieve uniform power sharing and input/output electrical isolation
without conflicts in the system output voltage regulation.
The parallel-connected source or independent ac power
sources may possess different frequencies, phases, and
voltages. Current-sharing control approaches are blended
with existing control of back-end commercial-off-the-shelf
converters. Here, the converter outputs are parallel connected across a common load, and uniform current sharing among the channel-output currents is achieved while
maintaining output voltage regulation performance. These
control approaches are also applicable to distributed ac
power sources, each of which is independently connected
to the input of the respective ac-to-dc power channel, resulting in multiple channels of distributed ac-to-dc power
systems that equally share their power flows into the same
load.
A. W. Bushmaker, “Systems, Methods, and Apparatus for Generating Terahertz Electromagnetic Radiation,” U.S. Patent
No. 8,357,919, January 2013
Terahertz (THz) radiation refers to electromagnetic waves
propagating at frequencies between the infrared and microwave regions of the spectrum, generally 0.3–3 THz. Despite
the promising applications of this technology, the availability of compact, reliable sources of THz waves is still limited.
This invention for generating THz waves involves coupling
a terahertz electromagnetic resonator with an optical resonator, where the optical resonator is made from nonlinear
optical material. Directing laser light through the optical
resonator generates THz radiation by parametric interaction of the two resonators through the nonlinear material.
In a preferred implementation of this invention, a FabryPérot optical resonator is placed in the electrode gap of a
metallic split-ring THz resonator.
M. H. Abraham and D. P. Taylor, “Systems and Methods for
Preparing Freestanding Films Using Laser-Assisted Chemical Etch, and Freestanding Films Formed Using Same,” U.S.
Patent No. 8,368,155, February 2013
Laser-assisted chemical etch (LACE) may involve exposing
a structure that includes a substrate and a film to a chemical etchant, such as chlorine gas, and to light. The substrate
may be selectively etched in regions exposed to the light
and to the chemical etchant, thus creating a cavity that frees
the film from the substrate in a selected region. However,
only selected types of structures have been prepared thus
far using LACE. Other references disclose forming channels in substrates beneath surface films, also by exposing
such structures to an etchant and to light. The structures
prepared using such methods are limited in the type of
channel that may be formed and/or the quality of the
surface film remaining after processing. In this invention,
freestanding films are prepared by diffusively delivering
an etchant to the substrate through a surface film while
transmitting laser light to the substrate via the surface film.
Together, the etchant and the laser light isotropically define
a cavity in the substrate beneath the surface film. The diffusive nature of the etchant delivery obviates the need to
provide access holes through the film, which may otherwise detrimentally affect the structural integrity of the film.
In other embodiments, the freestanding films have any of
a variety of suitable compositions besides silicon dioxide
or silicon nitride. For example, the films may be multilayer
films and/or may include hafnium oxide, diamondlike carbon, graphene, or silicon carbide of a predetermined phase.
Such films may include access holes defined to facilitate
etching of the underlying substrate.
T. Grycewicz, “Imaging Geometries for Scanning Optical Detectors with Overlapping Fields of Regard and Methods for
Providing and Utilizing Same,” U.S. Patent No. 8,368,774,
February 2013
Overlapped (i.e., staggered) time delay and integrated
(TDI) scanning arrays with interlaced columns can provide
up to twice the effective resolution of conventional TDI
focal plane arrays with the same pixel size when operated
under nominal conditions. However, especially when the
overlapped TDI arrays are physically separated on the
camera focal plane, image drift can destroy the alignment
that allows for superresolution reconstruction of the overlapped images. It would be useful to be able to decrease the
susceptibility of overlapped TDI arrays (or other optical
detectors arranged with overlapping fields of regard) from
loss of high-resolution performance in the presence of image drift. It would also be beneficial to be able to improve
the tolerance of overlapped-array imaging technologies to
scan rate errors. In addition, it would be useful to be able
to minimize (or decrease) the conditions under which image drift results in severe degradation of the resolution gain
potentially realized from the use of staggered arrays. In this
invention, imaging devices and techniques use multiple
optical detectors, and, in particular, imaging geometries,
for imaging devices that include three or more optical
detectors with overlapping fields of regard. The imaging
geometries are determined and provided in consideration
of one or more performance criteria evaluated over multiple operating conditions for the process of generating a
reconstructed image from the captured images. Example
embodiments involve arrangements of subpixel spacing
for overlapped imaging arrays (or other optical detectors
arranged with overlapping fields of regard) that decrease
the susceptibility of the overlapped arrays to loss of highresolution performance in the presence of image drift. By
way of example, physical and/or virtual arrangements of
subpixel spacing of three or more overlapped imaging arrays are determined in consideration of a process in which
an image is generated (e.g., reconstructed) from outputs of
three or more imaging arrays.
H. Helvajian, W. W. Hansen, and L. F. Steffeney, “Photostructured Electronic Devices and Methods for Making Same,”
U.S. Patent No. 8,369,070, February 2013
Photostructurable glass ceramic materials are used to make
structures that have internal functional surfaces, which
are defined during or after the photostructuring process.
A number of approaches are possible and depend on the
material constituents and concentration. If the material
has a high-enough metal concentration, then conducting
lines can be directly precipitated from the glass by a laser
direct-write patterning technique. An alternative approach
is to fill a photostructured cavity with gases that, under
ultraviolet light or high temperature, produce photolyse/
pyrolize electrically conducting material. The cavity can
also be filled by a conducting paste that is forced into the
channels by applied pressure through hydraulic action. The
three-dimensional electrically conducting structures are
encapsulated within an electrically insulating shell. One
practical example is in the use of electromagnetic applications (i.e., complexly shaped antennas for high-frequency
applications) where the delicate electrically conducting
antenna structure formed is surrounded by an insulating
package that protects it, but also has low radio-frequency
attenuation.
C. C. Reed, T. R. Newbauer, and R. Briet, “Computer-Implemented Systems and Methods for Detecting Electrostatic
Discharges and Determining Their Origination Locations,”
U.S. Patent No. 8,370,091, February 2013
Electrostatic discharges (ESD) on solar cells are triggered
when electrical field strengths become high enough to
induce the transport of charges. Subsurface blisters, voids,
and other manufacturing defects, as well as metal whiskers,
can, in a charging environment, produce the field strengths
needed to induce an electrostatic discharge. Micrometeoroid impacts are another potential trigger for ESD. Similar
mechanisms apply to other exposed satellite surfaces. No
viable techniques for locating the origination point of ESD
events have been implemented, yet knowing where ESD
events originate from would be useful in developing mitigation of anomalies from ESD on future space systems, and
in improving operating procedures of current and future
space systems. This invention is directed at computerimplemented systems and methods for detecting ESD on a
surface, and determining the original location of an ESD.
The surface may be, for example, a solar panel. In various
embodiments, a programmed computer device monitors
time-varying current data (i.e., current transients) related
to the surface to detect ESD on the surface. Also, the current profile or signature for the surface (i.e., the variation of
current level over a time period) may be compared to a catalog of ESD current profiles, where each ESD profile corresponds to a different location on the surface (e.g., the solar
panel). The location on the surface whose corresponding
ESD current profile best matches the actual current profile
from the ESD determines the original location of the ESD.
Moderately different processes may be used to determine
the ESD originating location depending on the shape of the
surface (i.e., whether it is symmetrical or irregular, or flat or
curved in three dimensions).
G. Radhakrishnan and P. M. Adams, “Method for Growth of
High-Quality Graphene Films,” U.S. Patent No. 8,388,924,
March 2013
Existing methods for making graphene include exfoliation
from highly oriented pyrolytic graphite, desorption of silicon from silicon carbide single crystals, and chemical vapor
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deposition from gaseous methane/hydrogen mixtures.
These methods, however, have limitations because they
do not offer large-area, single-layer graphene or produce
graphene with small single-crystal grains, which results in
numerous grain boundaries. Thus, there exists a need for
alternative methods for large-scale synthesis of monolayer
graphene over large areas that would be highly ordered
and would have large single-crystal grains. This invention addresses these needs by producing a highly ordered,
single-layer graphene film with large single grains of 10–30
square microns. According to this method, graphene films
are formed on a substrate held in a heated reactor using an
inert buffer gas to transport vapor from an oxygen-containing liquid hydrocarbon precursor, such as methanol, over
the heated substrate.
S. W. K. Yuan and D. G. T. Curran, “Variable Phase Shift Devices for Pulse Tube Coolers,” U.S. Patent No. 8,408,014,
April 2013
Pulse tube cryocoolers do not have moving parts at the
cold end, such as displacer pistons or valves. To achieve
the desired cooling, the combination of the phase control
device and the reservoir causes a phase shift between mass
waves and pressure waves generated by the compressor. By
restricting or slowing the mass flow to the buffer volume,
the phase control device may serve to shift the phase of the
mass flow relative to the pressure wave generated by the
compressor. This invention is directed to pulse tube coolers
that have flow resistance devices that are variable within
the thermodynamic cycle of the pulse tube. An example
pulse tube may be comprised of a compressor, regenerator,
and reservoir. A working fluid may be positioned within
the regenerator, pulse tube, and reservoir. Further, a variable phase control device may be positioned in a fluid path
between the pulse tube and the reservoir. The pulse tube
cooler may also have a control circuit. The control circuit
may be programmed to determine a position of the pulse
tube cooler in its thermodynamic cycle and vary a characteristic of the variable phase control device based on the
position of the pulse tube cooler in its thermodynamic
cycle.
R. Kumar, “Receiver for Detecting Signals in the Presence of
High-Power Interference,” U.S. Patent No. 8,433,008, April
2013
Command and telemetry constitute two of the most important subsystems of the U.S. Air Force space lift range system, which is designed to provide operational support for
space launch vehicles. A command destruct signal (CDS)
is sent to the launch vehicle if the trajectory of the vehicle
poses any serious safety concerns. While the need to issue a
CDS command happens infrequently, safety considerations
require that this signal/link have high reliability under all
conditions. It is also necessary to ensure that the command
uplink can be closed with sufficient margin under the
worst possible conditions and from any intended launch
sites. Under normal operating conditions, when the only
significant disturbance is the receiver thermal noise, there
is no real concern in terms of providing such a margin, as
has been shown in previous analyses. However, in the presence of high-power pulse interference, the performance
of the traditional command receiver is very poor in that
there is virtually no detection possible with such a receiver.
In one aspect, the present invention is directed to a radio
frequency (RF) receiver for CDS, although it could be used
to receive different types of signals as well. According to
various embodiments, the RF receiver is comprised of an
RF section, a down converter to intermediate frequency, a
down converter to complex baseband, a pair of analog-todigital converters, and a digital signal processor (DSP). The
DSP processes the complex baseband signal available at the
output of the down converter to complex baseband so as
to optimally estimate the amplitudes of various character
tones and the pilot tones that are present in the CDS signal, along with estimates of the associated signal-to-noise
power ratios for the various tones.
M. P. Ferringer, R. S. Clifton, and T. G. Thompson, “Systems
and Methods for a Core Management System for Parallel
Processing of an Evolutionary Algorithm,” U.S. Patent No.
8,433,662, April 2013
The goal of multiple-objective optimization, which is in
stark contrast to single-objective, where the global optimum is desired (except in certain multimodal cases), is to
maximize or minimize multiple measures of performance
simultaneously, maintaining a diverse set of Pareto-optimal
solutions. Classical multiple-objective optimization techniques are advantageous if the decision maker has some
prior knowledge of the relative importance of each objective. Despite these advantages, real-world problems, such
as satellite constellation design optimization and airline
network scheduling optimization, challenge the effectiveness of classical methods. When faced with a discontinuous
and/or nonconvex objective space, not all Pareto-optimal
solutions may be found. Additionally, the shape of the
front may not be known. These methods also limit discovery in the feasible solution space by requiring that the
decision maker apply some sort of higher-level information before the optimization is performed. Furthermore,
only one Pareto-optimal solution may be found with one
run of a classical algorithm. According to this invention,
there is a method for parallel processing of an evolutionary algorithm. The method may include identifying by a
manager processor for a processing environment a plurality of arriving processors available for use; configuring by
the manager processor a first number of the plurality of
arriving processors as master processors for the processing
environment; configuring by the manager processor a re-
spective second number of the plurality of arriving processors as slave processors; and reconfiguring by the managing
processor a current number of slave processors assigned
to one or more respective master processors based upon
the respective timing data calculated for the one or more
respective master processors.
N. P. Wells and J. C. Camparo, “Systems and Methods for Stabilizing Laser Frequency Based on an Isoclinic Point in the
Absorption Spectrum of a Gas,” U.S. Patent No. 8,442,083,
May 2013
One system in which frequency stabilization may be useful is ultraminiature atomic physics (UAP), in which diode
lasers are routinely used for spectroscopy and/or optical
pumping. The chip-scale atomic clock and the chip-scale
atomic magnetometer are examples of UAP systems. One
problem with such systems is that their overall size and
power may be severely constrained. Moreover, the atomic
phenomena may occur under physical conditions that
may bring new and sometimes significant dimensions to
the atomic physics as compared to macroscopic laboratory
experiments. As such, the stability of the laser frequency
in some circumstances may be critical, not only because
variations in frequency yield variations in the spectroscopic
signals of interest, but also because shifts in laser frequency
may alter the atoms’ energy-level structure through a lightshift effect. For this invention, the isoclinic point is a point
in the absorption spectrum of a gas that falls in between
two overlapping absorption peaks of substantially equal
amplitude, and which experience substantially the same
broadening as a function of a physical parameter. Because
the two peaks have equal amplitude, the isoclinic point is
a saddle point (local minimum) in the region of overlap
between the two peaks. As the peaks are evenly broadened
from a change in the physical parameter, the frequency
of the isoclinic point does not significantly change, but
instead remains at a constant frequency, independent of
the physical parameter. As such, by locking the laser to the
frequency of the isoclinic point, the laser is significantly less
susceptible to frequency variations than if the laser were
locked to an absorption peak.
J. T. Chou, T. S. Rose, and J. A. Conway, “Time-Domain Gated
Filter for RF Communication Systems,” U.S. Patent No.
8,443,024, May 2013
This invention is a photonic method for generating single
sideband (SSB) modulated radio frequency (RF) signals,
thereby reducing bandwidth requirements of system components. Simple modulation of an RF signal onto an optical
carrier generates upper and lower sidebands. The double
sideband (DSB) signal requires the system bandwidth to
accommodate twice the frequency range of the imparted
information or modulation. There are two primary methods to achieve SSB modulation: phase discrimination and
optical filtering. In the phase discrimination approach, an
RF hybrid coupler and balanced optical modulator are required. The full bandwidth capability of available RF hybrid
couplers, however, is limited to 10 seconds of gigahertz.
Greater bandwidths can be achieved using optical filtering
approaches. In the simplest approach, the DSB RF signal
is imposed on an optical carrier and passed through an
optical filter to remove the upper or lower sideband. This
filtering method, however, is possible only when the optical
carrier frequency is fixed and stable. In the time domain
filter approach, the DSB signal is first given a chirp (the
carrier frequency is given a linear frequency sweep) and
then passed through a compressor. The compressor creates
a time-domain image of the frequency spectrum so that
the upper- and lower-frequency sidebands are separated in
time. This signal passes through a time gate that removes
one of the sidebands. The resulting signal is then sent
through an expander to recreate the original modulated
signal with one frequency sideband removed. As such, the
time domain filter converts a DSB signal input into an SSB
signal output.
S. La Lumondiere, T. Yeoh, M. S. Leung, N. A. Ives, W. T. Lotshaw, and S. C. Moss, “Refraction Assisted Illumination for
Imaging,” U.S. Patent No. 8,450,688, May 2013
One method of imaging through substrate material is conventional bright field microscopy. According to bright field
microscopy, illumination is provided in a direction normal
to the substrate surface. An image is captured with a camera or other imaging device that is also oriented normal to
the substrate surface. While this technique can be relatively
inexpensive, the resolution of the resulting images is often
disappointing. The resolution of bright field microscopy
can be enhanced by applying an antireflective coating to
the substrate. This method, however, is expensive and requires that the target semiconductor chip be subjected to
one or more additional processing steps. This invention is
directed to systems and methods of imaging subsurface
features of objects. An illumination source may be directed
toward a surface of an object comprising subsurface features, wherein the illumination from the source is directed
at a first angle relative to the normal area of the surface.
The object may have a portion between the subsurface features and the surface, with the portion having an index of
refraction that is greater than the medium surrounding the
object. An imaging device may be placed with an objective
lens oriented normal to the surface. The first angle may be
larger than an acceptance angle of the objective lens.
F. T. Sasso and W. H. Chung, “High Frequency, Hexapod Six
Degree-of-Freedom Shaker,” U.S. Patent No. 8,453,512,
June 2013
State-of-the-art gyroscopes for space and other applications
require realistic laboratory environments to test and charCROSSLINK FALL 2014 51
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acterize performance. One popular type of gyro for space
applications is fiber optic gyros, which have recently been
found to be susceptible to low-level vibration. This effect
manifests itself as abrupt shifts in bias, which can be detrimental to operations. This phenomenon was not identified
using standard gyro test techniques and has been shown
to be extremely nonlinear. This invention is directed to a
shaker for enabling the testing of gyros and other devices
for performance under realistic six-degrees-of-freedom
motions (e.g., spacecraft motions). The shaker may be
implemented as a hexapod, comprising a top plate and six
individually and simultaneously controllable strut assemblies that are capable of extending and contracting linearly.
The strut assemblies can then be controlled by a closedloop, programmable controller to enable the plate to move
linearly in all three directions and rotate about all three
axes. The strut assemblies may comprise high-precision,
linear electromagnetic actuators, such as voice coil actuators. The strut assemblies may also comprise high-precision
noncontact sensors to sense the extension/contraction of
the strut assemblies along their stroke length. In addition,
the strut assemblies may comprise, at each end thereof,
stiff, bendable flexures to attain the repeatable and linear
motion required.
C. C. Reed and R. Briet, “System and Method for Detecting
Defects,” U.S. Patent No. 8,466,687, June 2013
During or after the manufacture of an article, defects may
be found that are difficult to detect from a visual inspection of the article’s exterior. In some cases, the defects are
present under an exterior surface of the article, such as a
surface coating. Subsurface defects and other types of hardto-observe flaws may have a number of undesirable consequences. In space systems, subsurface defects may degrade
thermal control surfaces because of compromised paint;
increase the likelihood of electrostatic discharges (ESD) on
satellites; diminish ESD mitigation on solar cells from coating loss; permit contamination of optical components from
surface peeling and flaking; or cause rocket motor failure
because of delamination of composite materials. Thermography is one example of a nondestructive evaluation and
testing (NDET) technique for detecting subsurface defects.
Thermographic techniques generally involve subjecting a
test article to a thermal pulse followed immediately by an
examination/evaluation of surface temperature differences
using an infrared camera. A possible disadvantage is that
the thermal pulse may cause new defects if the test article
contains volatile materials in microcracks, or if the composition of the test article includes materials with mismatched
coefficients of thermal expansion. More benign NDET
techniques are desirable. In this invention, various aspects
of a nondestructive evaluation and testing system, including a charge source and at least one voltage measurement
device, are disclosed. The charge source is for generating a
charging environment to produce either a voltage profile
and/or a current on an area of dielectric material disposed
over a conductive substrate. The area of dielectric material includes one area containing a subsurface defect and a
second area that is defect-free. The voltage measurement
device is for outputting voltage measurements at different
positions over the area of dielectric material. The voltage
measurements over the first area differ from the voltage
measurements over the second area to define a voltage
differential, and the locations where this voltage change occurs identify the boundary of the defect.
J. J. Poklemba, “Systems and Methods for Sliding Convolution
Interpolating Filters,” U.S. Patent No. 8,489,662, July 2013
Digital data transmission systems have traditionally been
designed for specific applications to accommodate relatively narrow ranges of data rates. Continuously variable
rate transmitter and receiver systems, however, could
provide certain desirable flexibilities. Unfortunately, to accommodate flexible up-sampling on the transmitter side
or down-sampling on the receiver side, traditional data
transmission systems have grown in size and hardware
complexity. Hence, the classical hardware solution may
experience an order of magnitude growth for each factor of
ten increase in the sample rate. Another popular alternative
to alleviate impractical hardware growth is the repeated use
of commonplace, multiply-accumulate (MAC) functions in
digital signal processing. However, this technique alone requires that the MAC run at integer multiples of the sample
rate, greatly restricting top-end speeds. A need remains
for improved systems and methods for up-sampling filters.
According to this invention, a system is provided for implementing a multirate digital interpolating filter. The system
includes a memory for storing finite impulse response
(FIR) aperture coefficients for spectral shaping. The system
also includes a processor configured to access the memory,
which is configured to up-sample symbol data, wherein
up-sampling comprises: convolving the symbol data with a
decimated FIR aperture coefficient set; convolving the symbol data with one or more shifted, decimated FIR aperture
coefficient sets; and summing up the convolution results
to produce interpolated, bandlimited data. The system
also includes an upconverter to modulate the interpolated,
bandlimited data.
M. P. Ferringer and T. G. Thompson, “Systems and Methods
for Generating Feasible Solutions from Two Parents for an
Evolutionary Process,” U.S. Patent No. 8,494,988, July 2013
The goal of multiple-objective optimization, in stark
contrast to the single-objective case where the global optimum is desired (except in certain multimodal cases), is to
simultaneously while maintaining a diverse set of Paretooptimal solutions. Classical multiple-objective optimiza-
tion techniques are advantageous if the decision maker
has some prior knowledge of the relative importance of
each objective. But despite these advantages, real-world
problems, such as satellite constellation design optimization, challenge the effectiveness of classical methods. These
methods also limit discovery in the feasible solution space
by requiring the decision maker to apply higher-level
information before the optimization is performed. This
invention may include: receiving a pair of parent chromosome data structures where each parent chromosome data
structure provides a plurality of genes representative of
variables that are permitted to evolve; combining genes of
the two parent chromosome data structures according to at
least one first evolutionary operator to generate at least one
first child chromosome data structure; evaluating at least
one first child chromosome data structure according to a
plurality of constraint functions to generate a respective
plurality of constraint function values for each of the first
child chromosome data structures, where the constraint
functions define constraints on a feasible solution set; determining whether any of the first child chromosome data
structures is within the feasible solution set based upon the
respective plurality of constraint function values, where
the prior combining, evaluating, and determining steps are
repeated for a number of first iterations until a first child
chromosome data structure is determined to be within the
feasible solution set or until a first maximum number of
first iterations has been reached.
M. P. Ferringer and T. G. Thompson, “Systems and Methods
for Box Fitness Termination of a Job of an Evolutionary
Software Program,” U.S. Patent No. 8,498,952, July 2013
The goal of multiple-objective optimization, in stark
contrast to the single-objective case where the global optimum is desired (except in certain multimodal cases), is to
simultaneously while maintaining a diverse set of Paretooptimal solutions. Classical multiple-objective optimization techniques are advantageous if the decision maker has
some a priori knowledge of the relative importance of each
objective. However, despite these advantages, real-world
problems, such as satellite constellation design optimization, challenge the effectiveness of classical methods. These
methods also limit discovery in the feasible solution space
by requiring the decision maker apply some sort of higherlevel information before the optimization is performed.
This invention may include: receiving a respective plurality of objective function values for each chromosome data
structure of a population of chromosome data structures,
where the respective plurality of objective function values
are obtained based upon an evaluation of each chromosome data structure by a respective plurality of objective
functions; mapping the respective objective function values
to respective epsilon values, where the respective epsilon
values define a respective address associated with the plurality of objective functions; performing nondomination
sorting of the population of chromosome data structures to
generate a reduced population of chromosome data structures based upon an evaluation of the respective plurality
of objective function values; and performing epsilon nondominated sorting according to an optimization of the plurality of objective functions and the defined respective addresses to identify an elite set of addresses, where the prior
steps are performed for a current generation, where the
elite set of addresses are compared to a prior elite set of addresses for a predetermined number of prior generations to
determine one or more variance values, and where the one
or more variance values are utilized to determine whether a
current job of an evolutionary algorithm is to be halted.
M. P. Ferringer, R. S. Clifton, and T. G. Thompson, “Systems
and Methods for an Application Program Interface to an
Evolutionary Software Program,” U.S. Patent No. 8,504,496,
August 2013
The goal of multiple-objective optimization is to maximize
or minimize multiple measures of performance simultaneously while maintaining a diverse set of Pareto-optimal
solutions. Classical multiple-objective optimization techniques are advantageous if the decision maker has some
prior knowledge of the relative importance of each objective. Because classical methods reduce the multiple-objective problem to a single objective, convergence proofs exist
assuming traditional techniques are employed. However,
despite these advantages, real-world problems, such as satellite constellation design optimization and airline network
scheduling optimization, challenge the effectiveness of classical methods. This invention may include a memory for
storing computer-executable instructions for an application
program interface, and a processor in communication with
the memory. The processor may be configured to execute
the computer-executable instructions to enable a user of
the application program interface to: specify parameters
associated with an evolutionary algorithm, where an execution of the evolutionary algorithm is in accordance with the
specified parameters; define a chromosome data structure
that includes a plurality of variables that are permitted to
evolve in value in accordance with the execution of the
evolutionary algorithm to generate one or more child
chromosome data structures; identify one or more objective functions for evaluating chromosome data structures,
including the generated one or more child chromosome
data structures; and define an output format for providing
one or more optimal chromosome data structures of the
evaluated generated child chromosome data structures as
designs to the identified objective functions.
K. Chiou and S. L. Osburn, “Systems and Methods for an Advanced Pedometer,” U.S. Patent No. 8,510,079, August 2013
BOOKMARKS
Some prior pedometers estimate the distance traveled by
counting the number of steps and multiplying by an average person’s stride length. However, nonstandard stride
lengths and a variety of other factors are sources of error
in the estimated distance traveled. Other pedometers use
accelerometers and a barometer to estimate the distance
of each step. However, these pedometers do not provide
calibration for accelerometer drift, and thus, the accuracy
of the measured steps varies greatly over time. Some or all
of the above needs and problems may be addressed by this
invention. According to this invention, the advanced pedometer can include a first accelerometer for providing first
acceleration information for a first direction; a second accelerometer for providing second acceleration information
for a second direction; a third accelerometer for providing
third acceleration for a third direction, wherein the first,
second, and third directions are independent of each other;
a clock for providing time information associated with
the first, second, and third acceleration information; and
a processing module comprising one or more processors.
The processing module is configured to receive the first,
second, and third acceleration information, and is further
configured to execute computer-executable instructions
to determine fourth-level acceleration information for a
plane using the first acceleration information for the first
direction and the second acceleration information for the
second direction, wherein the plane is defined by the first
direction and the second direction, and estimate a distance
traveled using the fourth-level acceleration information,
the third acceleration information, and at least a portion of
the time information. This invention uses a zero velocity
filter update to reduce drift between steps, and, rather than
counting steps or attempting to dead reckon in three-space,
the method of this invention integrates the distance traveled along a curvilinear path, similar in concept to the way
a car odometer measures the distance traveled by a car.
P. A. Dafesh, R. S. Prabhu, and E. S. Valles, “Cognitive AntiJam Receiver Systems and Associated Methods,” U.S. Patent
No. 8,515,335, August 2013
Existing antijam and interference mitigation techniques are
based on the assumption that the nature of interference is
previously known. Thus, these existing techniques use fixed
antijam and interference mitigation techniques. However,
these fixed techniques are not well suited in situations
where the nature of the interference changes unpredictably
or where the nature of the interference is not previously
known. According to this invention, a cognitive antijam
receiver system may include a signal analysis module that
processes a baseband signal to determine one or more
signal characteristics of the signal; a cognitive decision
unit that receives one or more signal characteristics from
the signal analysis module and generates at least one first
adaptive parameter; and an antijam processing module
that processes the baseband signal to generate a modified
signal that reduces the impact of the jammer signal on the
quality of reception of the desired signal from the baseband
signal, where processing by the antijam processing module
is based on the received first adaptive parameter from the
cognitive decision unit. The system may also include the
cognitive decision unit further generating a second adaptive parameter, and a receiver signal processing module
that processes the modified signal from the antijam processing module to extract information about the desired
signal from the modified signal, where processing by the
receiver signal processing module is based on the received
second adaptive parameter from the cognitive decision
unit.
A. J. Gallagher, “Methods and Systems for Detecting Temporally Oscillating Sources in Video Signals Using a Recursive
Infinite Impulse Response (IIR) Filter Technique,” U.S. Patent No. 8,532,197, September 2013
In recent years, the availability of high-speed generalpurpose computing systems and digital video recorders has
allowed the advancement of techniques for detecting and
finding scene content in video sequences. The fast Fourier
transform (FFT) is a well-known and widely used technique for decomposing signals into periodic components
and has been employed extensively in the realm of signal
processing, to include cases where the signal consists of a
single image pixel with time-varying amplitude. However,
in the case of imagery and video, where charge-coupled
device arrays can include very large numbers of pixels,
the FFT method applied to each pixel vector becomes
computationally expensive. Moreover, if FFT were applied
to temporal video analysis, using the full FFT for signals
with known periodic structure would result in a significant waste of computation time on irrelevant frequency
components. It would be useful to be able to provide scene
content detection methods and systems that overcome one
or more of the deficiencies of prior approaches to temporal
video analysis. The methods and systems of this invention
facilitate detection of temporally oscillating sources in digital video signals. Such methods and systems can be implemented to provide temporal target detection, as well as
target localization, tracking, tagging, identification, status
indication, and low-rate data transfer. Additional applications for the techniques include object recognition, pixel
classification, scene analysis, computer vision, and robot vision, as well as any process involving a video reference from
which it is desirable to extract one or more modulation
frequencies from the video data.
S. W. Janson and J. K. Fuller, “Systems, Methods, and Apparatus for Sensing Flight Direction of a Spacecraft,” U.S. Patent
No. 8,538,606, September 2013
Small satellites have low weights and small sizes, to reduce
launch cost to orbit. A 1 unit CubeSat, for example, weighs
about 1 kilogram, occupies a volume of about 1 liter, and
has a limited amount of available room for auxiliary systems, such as a flight direction sensor system for efficient
orbital positioning. Previous approaches to flight direction
sensing have involved calculation of the satellite attitude via
combinations of sun, star, Earth horizon, and other sensors.
However, such approaches often require multiple sensors
and complex imaging systems that can be prohibitively
bulky. The atmosphere rotates with the planet, so spacecraft in low Earth orbit fly through this atmosphere at 7 to
8 kilometers per second. Pressure-sensing approaches to
determining flight direction include direct physical sensing of the pressure difference between leading and trailing edges of the spacecraft, or monitoring neutral wind
direction. These approaches work best at low (less than
500 kilometer) altitudes where the atmospheric density is
readily detectable. However, the atmospheric density drops
rapidly with increased altitude, and therefore, detecting
flight direction using pressure sensing becomes almost impossible at altitudes greater than 1000 kilometers. According to this invention, a system is provided for determining
flight direction of a spacecraft. The system includes a nadir
direction finder, a power source, an onboard gyroscope,
and an imaging detector attached to the spacecraft. The
imaging detector is configured to acquire sequential images
of a portion of a celestial body, and further configured to
process the sequential images. The system also includes a
flight computer that is in communication with the imaging
detector and configured to execute computer-executable
instructions for determining the spacecraft flight direction
relative to the celestial body, based in part on the processing of the sequential images.
R. J. Zaldivar and J. P. Nokes, “Hybrid Adhesive,” U.S. Patent
No. 8,551,287, October 2013
The use of atmospheric plasma treatment process can be
an excellent method for the surface preparation of graphite
epoxy composites prior to bonding. However, many highperformance composite structures currently used for space
applications use a cyanate ester matrix material, not epoxy.
Cyanate ester composites have many improved properties
when compared with epoxies used in similar applications.
Unfortunately, studies show that the bond performance of
plasma-treated cyanate ester composites do not improve
to the same degree as select plasma-treated epoxies. The
chemical structure that contributes to many of these improved properties makes cyanate ester resins more resistant
to forming the bond-enhancing species. This invention
describes how to fabricate a tailored hybrid composite system with improved bond performance, taking advantage
of a secondary surface layer or film that is cocured with the
substrate. The hybrid system is able to form higher concen-
trations of the bond-enhancing active species during atmospheric plasma treatment than in the initial unmodified
system. This hybrid adhesive improves bond performance
without compromising the superior properties of cyanate
ester composites.
T. J. Grycewicz, “System and Method for Super-Resolution
Digital Time Delay and Integrate (TDI) Image Processing,”
U.S. Patent No. 8,558,899, October 2013
In conventional time delay and integrate (TDI) processing, the image motion across the array must be parallel
to the array columns to avoid image smear. Likewise, the
image motion across the array must be precisely locked
to the array line rate to avoid smear. According to this
invention, image drift is deliberately introduced in both
dimensions and output data are sent to a super-resolution
processing algorithm, which uses this drift to produce an
image with up to twice the effective resolution possible
with a conventional TDI imager. The imaging geometry is
set up such that a predictable subpixel component of the
frame-to-frame image motion can be used to construct a
high-resolution output image from multiple undersampled,
low-resolution input images. This combines the benefits of
TDI imaging with the benefits of super-resolution processing. In this invention, the TDI focal plane is rotated from
its normal orientation perpendicular to the scan direction.
This produces a predictable cross-scan drift. The line rate is
set to produce an in-scan drift. During image collection, a
sequence of images is saved, and the images are combined
on a high-resolution synthetic image plane (by, e.g., using
techniques developed for reconstruction of a high-resolution image from sequences of low-resolution images).
When the image drifts are accurately known and easily
controlled, image processing is easily and efficiently implemented, and the only additional resource required in the
processing chain is more memory. Alternately, if the drift
rates are not known or easily controlled, the image drift can
be estimated for each subimage, and the image reconstruction can be carried out as a postprocessing step.
CONTRIBUTORS
Charles L. Gustafson
Charles L. Gustafson, General Manager, Launch Systems Division, joined Aerospace in 1983. Today he manages launch system projects for a range of customers, with a current principal activity being the certification of the SpaceX
Falcon 9 (v1.1) system. He is a member of the Air Force Scientific Advisory
Board and was formerly the general manager of the Vehicle Systems Division,
and the principal director for the Transformation Communications Satellite
Program (TSAT). He has a B.S. in electrical engineering from Princeton University and an M.S. and Ph.D. in electrical engineering from the University of
California, Berkeley.
Siegfried W. Janson, Senior Scientist, Physical Sciences Laboratories, joined
Aerospace in 1987. He works on small satellite design, attitude sensors, and
orbital architectures. He is the principal investigator on the NASA-sponsored
Optical Communications and Sensors Demonstration, which is a high-speed
laser communications downlink from a low Earth orbit CubeSat to the ground.
He has a B.S. in astronautical engineering from Rensselaer Polytechnic Institute and an M.S. and Ph.D. in aerospace engineering from Cornell University.
Siegfried W. Janson
Internal Research and Development Spurs Advancement
and Fills Technology Gaps
T. Paul O’Brien
T. Paul O’Brien, Research Scientist, Space Sciences Department, joined Aerospace in 2002. He conducts scientific research into Earth’s radiation belts and
magnetosphere. He also develops space environment models and tools for satellite design, situational awareness, and anomaly resolution. He has a B.A. degree
from Rice University in physics and classics, and M.S. and Ph.D. degrees from
UCLA in geophysics and space physics.
2025 and Beyond: The Next Generation of Protected
Tactical Communications
Jo-Chieh Chuang
Joseph Han
Jo-Chieh Chuang, Senior Project Leader, Emerging Systems, MILSATCOM
Division, joined Aerospace in 1986. He has worked on several MILSATCOM
architecture studies, the AEHF program, and the TSAT program. He is the
Aerospace lead for the Air Force’s “Design for Affordability Risk Reduction”
project to develop and demonstrate the protected tactical waveform and protected tactical system concepts. He has a B.S. in mechanical engineering from
the National Cheng-Kung University in Taiwan; an M.S. in mechanical engineering from the University of Texas at Arlington; and a Ph.D. in mechanical
engineering from the University of Houston.
Joseph Han, Department Director, Network Systems, joined Aerospace in 1989.
He leads and performs system-level analyses and designs for various communication and network systems. He has a B.S. in electrical engineering from Soong
Sil University, Korea; an M.S. in electrical engineering from California State
University, Los Angeles; and a Ph.D. in electrical engineering from the University of California, Irvine.
Bomey Yang, Engineering Specialist, Communication and Network Architectures Subdivision, joined Aerospace in 2007. She leads and performs waveform
analyses as well as communication systems design studies for various MILSATCOM programs. She has a B.S. in computer science and engineering, and an
M.S. in electrical engineering from the University of California, Los Angeles.
Applying Systems Engineering to Manage U.S. Nuclear Capabilities
Bomey Yang
Matthew J. Hart
James D. Johansen
Matthew J. Hart, Principal Director, Civil Applications Directorate, Civil and
Commercial Programs, joined Aerospace in 1987. He has 26 years of experience
with the DOD, National Reconnaissance Office, and NASA, and currently manages the corporation’s support to a number of U.S. government civil customers.
He has a B.S. in aeronautics and astronautics from Purdue University and an
M.S. in aero-astronautics from Stanford University.
James D. Johansen, System Director, Department of Energy Programs, Civil
and Commercial Programs, joined Aerospace in 2008. He previously worked
at the MITRE Corporation, Lockheed Martin, and Boeing on space, terrestrial,
and information technology programs. He manages the Department of Energy
Programs Department and directs various interagency civil customer studies,
analysis of alternatives, technology development activities, and enterprise capability assessments. He has a B.S. and M.S. in electrical engineering from the
University of Southern California.
Mark J. Rokey, Senior Project Engineer, Civil Applications Directorate, Civil
and Commercial Programs, joined Aerospace in 2011. He has 26 years of experience with NASA and leads system-level analyses for various government projects. He has an M.S. in computer science from Texas A&M University.
Mark J. Rokey
Electric Propulsion at Aerospace
The Aerospace Corporation began the development of an electronic propulsion (EP) testing capability in the 1980s that has
since become one of the premier world facilities for the advanced
characterization of EP thrusters.
Courtesy of NASA
NASA's NEXT gridded ion engine.
The Aerospace electromagnetic interference test facility.
These capabilities have been applied to two key Air Force programs, Wideband Global Satellite Communication System (WGS)
and Advanced Extremely High Frequency (AEHF). WGS flies on
Boeing’s 702 bus using the XIPS 25 gridded ion engine manufactured by L3, and AEHF flies on Lockheed Martin’s A2100 bus using
the XR5 (also known as BPT-4000) Hall thruster manufactured by
Aerojet/Rocketdyne. Aerospace expertise and testing has provided
mission assurance and anomaly resolution for these programs.
Recent work at Aerospace has ranged from the very practical,
such as transitioning mature thruster designs to flight, to basic re-
Courtesy of the Massachusetts
Institute of Technology
The iEPS electrospray thruster.
Courtesy of NASA
Aerospace is well known for advanced diagnostics applied to
thruster characterization and their integration effects on spacecraft, e.g., various plasma probes and laser-based plume measurements. Aerospace was the first to apply a number of diagnostic
tools to the characterization of EP thrusters, perhaps most
notably electromagnetic radiation measurements. The Aerospace
Electromagnetic Interference Test Facility is unique in the world
and draws to Aerospace virtually all flight thrusters for testing
to ensure that thruster operations will not interfere with satellite
communications. Consequently, Aerospace maintains the most
comprehensive database on EP thruster measurements anywhere.
search on improving the fundamental understanding of the
plasma physics underpinning thruster operation. Recent collaborations with NASA Glenn Research Center have been critical in
advancing NASA’s Evolutionary Xenon Thruster (NEXT) 7-kW ion
engine to flight, as well as developing future higher-power annular ion engine designs.
NASA's annular ion engine.
Aerospace has also developed novel diagnostics for the characterization of miniature electrospray thrusters developed at the Massachusetts Institute of Technology for use on CubeSats. Aerospace
is also a leader in characterizing facility effects on Hall thruster
operation, which can severely hamper the ability to reliably predict
on-orbit performance using ground-based test and qualification
data.
Electric propulsion has come of age with recent announcements
from a number of U.S. and international contractors developing an
“all-electric bus” to provide mass/cost savings to customers. Aerospace has played an important historical role in the maturation of
EP technology, and continues to advance the state of the art.
–Thomas Curtiss, director, Propulsion Science Department
AeroCube 4C Delivers Stunning Photos
T
he Aerospace Corporation’s picosatellite team captured
these photographs (next page) shot from an unclassified
AeroCube satellite last fall. The photos display some of
today’s advanced technologies and the functionality of miniature
space components.
Picosats are being tested for use on many national security
space missions. Their reduced cost and quicker turnaround to
delivery make them a compelling and attractive choice for space
customers. Small satellites cannot replace the capabilities of
large satellites, but scientists and engineers continue to push the
boundaries of what they can do, and explore how these miniature
satellites may best serve the national security space community.
The AeroCube 4C is a 10 × 10 × 10 centimeter CubeSat built at
Aerospace. This CubeSat contains various first-of-a-kind mission
technologies including solar panel wings designed for efficient
formation flying; attitude control to better than 3 degrees accuracy; a 0.3 square meter deployable deorbit device; and subminiature reaction wheels.
Aerospace’s 2014 team of the year award went to the picosat
team, whose 22 members were recognized for “consistently
leading its field in innovation” and for “building groundbreaking spacecraft while meeting immensely restrictive budget and
scheduling requirements.”
THE BACK PAGE
A.
B.
E.
F.
I.
J.
C.
D.
G.
H.
K.
L.
A:
B:
C:
D:
Israel and Sinai
The Great Barrier Reef
Jamaica
Baja California
E: New Zealand
F: Himalaya Mountains
G: Grand Canyon
H: Los Angeles
I: Sahara’s Eye
J: Denali
K: Washington, D.C.
L: Aerospace research scientist Brian Hardy
examines images from space.
Crosslink
®
FALL 2014 VOL. 15 NO. 1
Editor-in-Chief
Nancy K. Profera
Illustration
Jason C. Perez
Joseph P. Hidalgo
Guest Editor
John V. Langer
Contributing Editors
Gabriel Spera
Richard K. Park
Staff Editor
Jon S. Bach
Research and Program
Development Advisor
Terence S. Yeoh
Art Direction and Design
Jason C. Perez
Richard M. Humphrey
Board of Trustees
Barbara M. Barrett, Chair
George K. Muellner, Vice Chair
Wanda M. Austin
Kevin P. Chilton
David M. DiCarlo
Michael B. Donley
Bonnie Dunbar
Keith P. Hall
Daniel E. Hastings
Tina W. Jonas
John E. McLaughlin
Michael Montelongo
Jeffrey H. Smith
K. Anne Street
Alan C. Wade
Robert S. Walker
Photography
Eric Hamburg
Elisa Haber
Editorial Board
Randy M. Villahermosa, Chair
David A. Bearden
Kevin D. Bell
Walter F. Buell
John E. Clark
Henry Helvajian
Michael R. Hilton
Diana M. Johnson
Jean L. Michael
Marilee J. Wheaton
The Crosslink Crossword
Crosslink 2014
1
2
4
Across
1. Talk show big shot
3. Military supply center
5. Dramatic situation
6. Politician's plan
7. Three is this
9. Like Plastic Man?
11. Polite
13. Kind of (plastic) card
14. Speedster's sport
16. Freewheeling music session
19. Hearty
21. Postpone (an agenda item)
23. Apple infrastructure
25. Sonic phenomenon
26. Movie building block
27. They're everywhere in L.A.
29. Put down (money)
30.Entrance
31. With "in," contribute
32. Airport building
33. Move backwards
34. Unclear mixup
Corporate Officers
Wanda M. Austin,
President and CEO
Ellen M. Beatty
Bernard W. Chau
Malissia R. Clinton
Manuel De Ponte
Rand H. Fisher
Wayne H. Goodman
David J. Gorney
Malina M. Hills
Ray F. Johnson
Randy L. Kendall
William C. Krenz
Howard J. Mitchell
Rami R. Razouk
Catherine J. Steele
Sherrie L. Zacharius
3
5
6
7
9
8
10
11
12
13
14
15
16
19
20
22
25
23
17
18
21
24
26
27
28
29
30
31
32
33
4. It's a long story
Across 8. Amount of medicine
Down
1. Talk show
big shot carry this
1. Beer plant
9. Investments
3. Military supply center
2. "Let me ___ your memory.
10. situation
"I'll huff & I'll puff..."
5. Dramatic
3. Supervisory body 6. Politician's
11. Vehicle
plan for verse greetings
7. Three is this
34
1 2.
13.
15.
17.
18.
A nurse may take yours
20. Run in different directions
Down
Celebrating Thanksgiving, e.g. 22. It's done on a runway
1. Beer plant
An airline's critical city
24. Consider again
2. "Let me ___ your memory."
Comedian's currency
28. Not
a poser
3. Supervisory
body
Sausages
30.story
Dieter's dread
4. It's a long
8. Amount of medicine
Most puzzle words
and clues
are fromMan?
articles in this issue. The solution is on the Crosslink Web site: http://www.aerospace.org/publications/crosslink/.
9. Like
Plastic
9. Investments carry this
11. Polite
13. Kind of (plastic) card
10. "I'll huff & I'll puff..."
11. Vehicle for verse greetings

- The Aerospace Corporation

Transcription

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