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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