Issue 6 (EADS Astrium) - The British Interplanetary Society

When did you last use a
satellite?
It is probably a lot closer than you think.
Satellites do a lot of jobs, they help us
talk to one another, they monitor our
weather and let us know where we are. We
use them to map our world and some help
to rescue ship wrecked sailors or get aid to
disaster areas.
Orbits
How do satellites stay in orbit?
Why don’t they fall down?
They do fall, but they fall around the
Earth. If you drop a stone over a cliff it
falls
about five metres in the first second. If
you throw it horizontally at 7900 metres
per second (that’s some throw) it still
falls five metres in the first second, but
by that time the Earth has curved away by
that same five metres. So it keeps going.
Eventually (after about 92 minutes) it would
get all the way around the Earth and hit you
in the back of the neck (if you were stupid
enough to still be standing there).
Where are they now?
Satellites fly in different orbits, depending on
what they do. The International Space Station
orbits at about 340 km above the Earth, at an
angle of 51.6º, so that the Space Shuttle and
the Russian Soyuz launcher can reach it. You
can find out where it is now at:
http://spaceflight.nasa.gov/realdata/tracking/
Envisat, the European Space Agency’s
Earth Observation satellite, has an orbit 783
km going over the poles, so it gets to see
everywhere on Earth twice a day. ESA has a
site tracking all its satellites at:
http://www.esa.int/SPECIALS/Track_ESA_
missions/index.html
The Hubble Space Telescope orbits at 600
km, circling the Earth every 96 minutes.
This allows it to be serviced by the Space
Shuttle.
The GPS navigation satellites fly in a
number of orbits at 20200 km, each at an
angle of 55º to the equator. This means that
there are always at least four satellites in the
sky from any point on the ground.
Communications satellites fly at an altitude
of 35845 km above the equator. They take
precisely 24 hours to circle the Earth, so
that they appear to hang in a fixed point in
the sky.
You can sometimes see one of the nearer
satellites just after sunset, because while
you are in darkness the satellite can still
be in sunlight. Use one of the tracking
sites to find out when one is going to go
over you.
If you thought GPS was just about SatNav
you were mistaken! Look deeper and you’ll
find GPS has many applications…
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GPS is used to timestamp all
transactions made at our cash
machines and in our banks
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Earth Observation satellites like
Envisat and Meteosat provide us
with accurate data used for weather forecasting.
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In the wake of the Tsunami in 2005
satellites provided vital information
to emergency services detailing the
areas most affected and helped get
aid to those areas.
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Earth observing satellites are
continually monitoring our planet
and the recording the changes
occurring due to global warming,
this data is used to try and help cut
emissions and try to prevent further
damage to our planet.
GPS timing is used in telephone networks
GPS is used by Taxi companies not only to
help them find the quickest route to a destination but also to track them from the call
centre such that when someone calls for a
taxi the nearest one to the pick up can be
sent.
And somethings you
might not realise initially came from
technology developed for use in space…
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Do you have Sky TV at home?
The SKY service is broadcast via
satellites. The signal is then relayed
to your home via the small “sky” dish
(receiving antenna) on the side of
your house.
All television channels are also
broadcast initially via satellites –
without the satellites there would be
no TV!
Satellite based communications help
us to keep in touch with one another
wherever we are in the world or in
space!
Lightweight blankets – these “foil”
blankets often used by runners at the
end of a race and by emergency services
were originally developed for protecting
satellites in space.
Smoke Detectors – originally
developed for use on the Skylab Space
Station, they are now found in virtually
every home.
Cordless Tools – now used everyday,
items like cordless drills were developed
for the Apollo astronauts and used during
the Moon landings.
All images credited to NASA and ESA
In every issue of Voyage some of your frequently asked questions
relating to space and space technology will be asked by our space
experts. Send in your questions for our experts and yours might appear
here.
1
Which was the first ever satellite in space?
The first satellite to be launched was Sputnik 1. Launched on 4
October 1957, Sputnik 1 was built by the Russians. It was the
creation of Sergi Korolov. Sputnik remained in orbit for 91 days before
burning up in the earth’s atmosphere.
2
How many satellites are orbiting the Earth?
It is estimated that there are approximately 8000 satellites in orbits
around the Earth.
3
How much does a satellite cost?
Different satellites cost different amounts. The large communications
satellites that broadcast our TV signals cost around $100 million GPS satellites cost around £150 million whereas scientific satellites like the Hubble telescope can cost around $2000 million.
4
How do satellites get into space?
Satellites are put into space by large rockets. These
rockets usually have stages, the first stage is used at
the beginning of launch to give the rocket the initial
boost into space. The second stage is then ignited
and finally the third stage is used to put the satellite
into it’s desired orbit.
Find the words in the word search below
describing space in your daily life.
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Victoria Hodges
Astrium Ltd, Stevenage, UK, Graduate Development Programme.
I’m a graduate engineer, recruited
into the Attitude and Orbit Control
Systems, Guidance Navigation
Control & Flight Dynamics Group
Stevenage, UK, working on formation
flying studies. I spent three months
working in Toulouse, France in the
Advanced Studies group (formation
flying) and currently working on
the Aeolus project doing Systems
Engineering and Operations support.
In my final year of university I decided
to apply to EADS Astrium, and was
taken onto their graduate programme,
a two year scheme designed to allow
new graduates to experience a wide
range of roles within the industry.
Although I always had an interest in
space, it wasn’t until I was in my final
year at secondary school (aged 15)
that I really thought about a career in
the space industry. This was mostly
thanks to my physics teacher at the
time who encouraged my enthusiasm
for the subject. Not knowing much
about engineering, I decided to follow
the physics route into space.
Send in your questions to our
space experts at:
Voyage,
BIS, 27/29 South Lambeth Rd,
London, SW8 1SZ
Email: [email protected]
Web: www.bis-space.com/education
Edited by Victoria Hodges (Astrium) and Bob Parkinson, Designed by Melanie David-Feveck
Published by the British Interplanetary Society. Registered Company No: 402498. Registered Charity No: 250556.