WASI-UMBRAS Occulter Testing
Transcription
WASI-UMBRAS Occulter Testing
UMBRAS Distant Screens: From Extrasolar Planets to Eclipsing the North Star Ian J. E. Jordan, December 6, 2005 Space Telescope Science Institute http://umbras.org http://westminsterastro.org • Mark Kochte, Dorothy Fraquelli, F. Hamilton, Charlie Wu. Ian Jordan –Computer Sciences Corporation @ STScI • Helen M. Hart –Applied Physics Lab • Paul Henze, George Sauter, Erich Bender, Brian Eney, Ron Smith –Westminster Astronomical Society, Inc. • Alfred B. Schultz, Richard Lyon, Peter Chen, Jan M. Hollis, Ken Carpenter, Jesse Leitner, Richard Burns, Scott Starin –NASA/Goddard • Fred Bruhweiler –CUA/IACS • Dennis Skelton • Bryce Roberts –U.C. Berkeley –Orbital Sciences Coproration • Ed Rowles –Blue Horizons • Zolt Levay –AURA • Glenn D. Starkman, Craig G. Copi – Case Western Reserve Univ. UMBRAS Core Investigators An Outline for this Evening… • Introduction: Extrasolar planets--to date. • History & Workings of External Occulters • Ground Demonstration w/ WASI participation. Successful Planet Finding Techniques Transit Direct Imaging & Coronography Candidates found: ~3 Courtesy L. Cook, exoplanets.org Candidates found: ~2-50 Microlensing Candidates found: ~2 Candidates found: ~130 Pulsar Timing Candidates found: ~4 Courtesy: Penn State & Alex Wolszczan Extrasolar Planet Count: 156, and growing! 2M1207 & GQ Lupi Ground-based & HST surveys are starting to yield direct images of planets, but these are very far away from their parent stars, very large, and/or very young. TPF: What is the problem? TPF: Terrestrial Planet Finder … Detect & study earth-like planets around nearby stars. • Earth < 0.” 1 from the sun when viewed from 33-light years away (diameter of a quarter at 50 km). • Sol appears 10-billion (1010) times brighter than earth. Occulter: “covering up” the star improves star-planet contrast. Before After Carl Sagan in COSMOS Episode 7 “The Backbone of Night.” COSMOS QuickTime™ and a decompressor are needed to see this picture. A Brief History of Occulters <1962 Robert Danielson, Princeton 1962 Lyman Spitzer, Princeton Infinite Half-plane analysis American Scientist “Beginnings & Future…” 1972 Su-Shu Huang, Northwestern 1974 Gordon Woodcock, Boeing 1978 Hugh S. Hudson, UCSD, et.al. 1978 James Elliot, Cornell Resurrected Spitzer’s analysis Occulter Vehicle Design Shuttle-borne Pinhole Occulter Facility Lunar occultation for LST, Hill Orbits 1980 Carl Sagan 1985 Christian Marchal, ONERA COSMOS "Backbone of Night" episode Spergel-Kasdin-like Screen Shapes 1995 Jean Schneider, Obs. de Paris 1997 G. Starkman, C. Copi, CWRU 1998 G. Starkman, C. Copi, CWRU 1998 Schultz, Jordan, Hart, et.al. SCODOTEP IRIS (opaque occulter) BOSS (apodizing occulter) UMBRAS (feasability studies) 2001 R. Lyon, A. Schultz, et.al. 2005 W. Cash, et.al. Occulter + Shaped Aperture /Apodization New Worlds Observer (Marchal occulter) Woodcock Occulter ~ 60-m diameter deployable “umbrella” packaged in a 2.5-m x 10-m upper stage. BOSS Variable Transmission Screen Occulter What is BOSS? -- It is a different kind of occulter mission. BOSS employs an apodizing occulter without using multiple PSF suppression stages within the telescope. Plot & Image courtesy of BOSS team, TRW, & JPL Bus closeup Tri-aspect Component Diagram Constellation Configuration in Space Operations Cycle T P F C + O Telescope-Occulter Control Block Diagram • • • • Telescope science imager takes picture(s) Pictures are measured to determine occulter position Error signal transmitted to occulter Occulter adjusts position & velocity Sunward view of UMBRAS Occulter Launching Multiple Occulters Transit Time: Function of Separations Differential Acceleration Magnitude (m/s2) Ambient Earth-Sun L2 Accelerations NSTAR acceleration level Science Ceiling Earth-Sun L2.20,000 km Telescope-Occulter separation, with non-saillike telescope & occulter properties for a likely typical TPF mission. • Brown solid = Δ-gravitational (earth) • Black dotted = Δ-gravitational (sun) • Green solid = ~Δ solar radiation pressure • Yellow solid = Δ-gravitational (m oon) • Blue dashed = max allowed gas leakage (10%) • Orange dotted = ~ nominal Δ solar wind Sun-Telescope-Occulter Angle (degrees) Why an Occulter? Point Spread Function Slices using a 4-metre Telescope ASA: WFQ = λ/1000 ASA + O: WFQ = λ/100 Better suppression of the stellar PSF wings even with lower wavefront quality. ASA = Apodized Square Aperture W F Q = W ave Front Quality Discovery Space Diagram Exoearths fainter than mV=32 not plotted. B6V A5V Exoearth mV=29.5 G0V K3V M1V M3V Alpha Cen A Alpha Cen B Tau Ceti Epsilon Eridani Pi3 Orion Epsilon Indi M4V M7V Dawes’ Limit 8-m V-band Dawes’ Limit 2.4-m V-band TPF-C goal. goal + minimal Occulter. Occulter vs Alternate Method Cost QuickTime™ and a TIFF (LZW) decompressor are needed to see this picture. FL = FresnelLens FFO = Free-Flying Occulter NIFF = Free-Flying Nulling Interferometer NIM = Monolithic Nulling Interferometer LAC = Large Aperture Coronagraph ULSA = Ultra-Large Sparse Aperture SIM = Space Interferometry Mission The New Worlds Observer/Imager Concept QuickTime™ and a TIFF (LZW) decompressor are needed to see this picture. Ground ‘Tests’ of Occulters W2 FN = z⋅λ W = FN ⋅ z ⋅ λ W = D ⋅ constant W=occulter width; z=separation; λ=wavelength; D=aperture. D∝ z D=4m; z=20,000 km D=9mm; z=100m Ground Test Equipment • • • • • • • F/5 Televue 101-mm refractor. Masked down to 11 & 24 mm. Optional Barlow: system f/# from 50 - 100. Mounted atop 8” + alt/az for stability. ST-7X, TEC-cooled, 768x512 CCD camera. M675X laptop data acquisition/storage. Green laser for optical alignment. • • • • • • • • Hand-crafted (P. Henze) occulter-rig. 12-inch diameter light shroud tube. Square-rail optical bench. Mid-tube occulter placement slot. 1- and 2-inch square occulters. 9” 1/10th-wave flat & mirror cell (GSFC). Alt-az mirror mount. Red laser for optical alignment. Pic 15 Pic 11 Pic 27 Pic 25 Pic 3 Pic 6 Pic 4 Experiment Field of View. 9” mirror 25-mm (~ 15 pixels) edge occulter August 7/8, 2004 626-second drift. 765 x 510 9-μ pixels, 540-mm focal length, distance ~ 95 metres Occultation Movie Watch for real QuickTime™ and a decompressor are needed to see this picture. diffraction lobes! Movie C QuickTime™ and a decompressor are needed to see this picture. 19:45 November 5, 2004, Drift 6, 24-mm aperture. Theory & Experiment: Comparison Admittedly, this is red and green apples, but . . . . Unapodization QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Sonine 4 Apodization • • • • Polychromatic Δλ/λ ~ 0.5, Circular aperture, Atmospheric induced wavefront error, Atmospheric smearing • Monochromatic, • Square aperture, • No wavefront error UMBRAS/WASI Occulter Demonstration Team October 31, 2004