ATLAST: Advanced Technology Large-Aperture Space Telescope

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ATLAST Advanced Technology Large-Aperture
Space Telescope
A NASA Astrophysics Strategic Mission Concept
Study of the Science Cases Technology
Developments needed to build an AFFORDABLE 8m -
16m UV/Optical Filled-Aperture Space Telescope

• Marc Postman
• STScI
• Pathways 2009, Barcelona, Spain

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Advanced Technology Large-Aperture Space
Telescope (ATLAST) Concept Study Team

• Ball Aerospace
• Vic Argabright Teri Hanson
• Paul Atcheson Leela Hill
• Morley Blouke Steve Kilston
• Dennis Ebbets
• Goddard Space Flight Center
• David Aronstein Rick Lyon
• Lisa Callahan Gary Mosier
• Mark Clampin Bill Oegerle
• David Content Bert Pasquale
• Qian Gong George Sonneborn
• Ted Gull Richard Wesenberg
• Tupper Hyde Jennifer Wiseman
• Dave Leckrone Bruce Woodgate

JPL Peter Eisenhardt Dave Redding Greg
Hickey Karl Stapelfeldt Bob
Korechoff Wes Traub John Krist
Steve Unwin Jeff Booth
Michael Werner Johnson Space Flight Center
John Grunsfeld Marshall Space Flight Center
Bill Arnold Phil Stahl Randall
Hopkins Gary Thronton John Hraba
Scott Smith Northrop Grumman Dean Dailey
Chuck Lillie Cecelia Penera
Ron Polidan Rolf Danner Amy
Lo Princeton University Jeremy Kasdin
Robert Vanderbei David Spergel
STScI Tom Brown Marc Postman,
P.I. Rodger Doxsey Neill Reid Andrew
Fruchter Kailash Sahu Ian Jordan
Babak Saif Anton Koekemoer Ken Sembach
Peter McCullough Jeff Valenti Matt Mountain
Bob Brown University of Colorado
Webster Cash Mike Shull Jim
Green University of Massachusetts Daniela
Calzetti Mauro Giavalisco
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Is There Life Elsewhere in the Galaxy?
Why is a large UVOIR space telescope required to
answer this question? Habitable Zones (HZ) of
nearby stars subtend very small angles (lt200
mas) Earth-mass planets within these HZ will be
very faint (gt29 AB mag) Requires high-contrast
(10-10) imaging to see planet. Cannot achieve
this from the ground. Number of nearby stars
capable of hosting potentially habitable planets
is not large (e.g., non-binary, solar type or
later). Sample size ? D3 Planets with
detectable biosignatures may be rare. May need to
search many systems to find even a handful.
Sample size ? D3
Need to multiply these values by ?Earth x fB to
get the number of potentially life-bearing
planets detected by a space telescope. ?Earth
fraction of stars with Earth-mass planets in HZ
fB fraction of the Earth-mass planets that
have detectable biosignatures
Number of FGK stars for which SNR10, R70
spectrum of Earth-twin could be obtained in lt500
ksec
If ??Earth x fB 1 then DTel
4m ???????Earth x fB lt 1 then DTel
8m ???????Earth x fB ltlt 1 then DTel 16m
To maximize the chance for a successful search
for life in the solar neighborhood requires a
space telescope with an aperture of at least
8-meters
Green bars show the number of FGK stars that
could be observed 3x each in a 5-year mission
without exceeding 20 of total observing time
available to community.
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F,G,K type stars whose HZ can be resolved by a
telescope of the indicated aperture for which a
R70 exoplanet spectrum can be obtained in lt500
ksec.
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R100 ATLAST Spectrum of 1 Earth-mass Terrestrial
Exoplanet at 10 pc
Reflectance ? (Planet Mass)2/3 5 Earth-mass 15.6
ksec on 8-m
Exposure 45.6 ksec on 8-m
7.8 ksec on 16-m
Bkgd 3 zodi Contrast 10-10
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R500 ATLAST Spectrum of 1 Earth-mass Terrestrial
Exoplanet at 10 pc
Reflectance ? (Planet Mass)2/3 5 Earth-mass 172
ksec on 8-m
Exposure 503 ksec on 8-m
56 ksec on 16-m
Bkgd 3 zodi Contrast 10-10
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Detecting Photometric Variability in Exoplanets
Ford et al. 2003 Model of broadband photometric
temporal variability of Earth
Require S/N 20 (5 photometry) to detect 20
temporal variations in reflectivity. Need to
achieve a single observation at this S/N in lt
0.25 day of exposure time in order to sample the
variability with at least 4 independent
observations per rotation period.
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Transit Spectroscopy Simulations of Super
Earthsby Clampin LindlerAssume M2 Star with
K-mag 6. Instrumental Effects have been modeled
assuming JWST-like spectrograph
8-m ATLAST
16-m ATLAST
Intermediate super-earth R 150 20 transits (P
22 days)
Intermediate super-earth R 150 20 transits
Able to retain substantial H2 in atmosphere
Super Earths have mass up to 10 x Earth
8-m ATLAST
16-m ATLAST
Intermediate super-earth R 150 100 transits
Hydrogen-rich super-earth R 500 20 transits
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ATLAST Concepts
8-m Monolithic Primary (shown with on-axis SM
configuration)
9.2-m Segmented Telescope
36 1.3-m hexagonal mirror segments
16.8-m Segmented Telescope
36 2.4-m hexagonal mirror segments
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Studying two architectures 8-m monolithic and
(9.2-m, 16.8-m) segmented mirror telescopes

• Monolithic Primary
• On and off-axis secondary mirror concepts
  investigated.
• Off-axis concept optimal for exoplanet
  observations with internal coronagraph but adds
  complexity to construction and SM alignment.
• Uses existing ground-based mirror materials. This
  is enabled by large lift capacity of Ares V cargo
  launch vehicle (55 mT).
• Massive mirror (20 mT) has 7 nm rms surface.
  Total observatory mass 44 mT.

• Segmented Primary
• Only studied designs with an on-axis secondary.
• Requires use of (relatively) lightweight mirror
  materials (15 - 25 kg/m2) efficient
  fabrication.
• 9.2m observatory has a total mass of 14 mT
  (16.8-m has a total mass of 35 mT).
• 9.2-m observatory can fly in EELV Does not
  require Ares V.
• Requires active WFSC system.

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Advanced Technology Large-Aperture Space
Telescope (ATLAST)
16.8-m in Ares V fairing (with extended height)
Ares V Notional 10 m Shroud
Delta IV H EELV
meters
8-m Primary installed in its fully deployed
configuration at launch.
8-m Monolithic Telescope
16.8-m Segmented Telescope
9.2-m Segmented Telescope
Observatory dry mass 44 mT
Observatory dry mass 14 mT
Observatory dry mass 35 mT
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Common Features for all Designs

• Diffraction limited _at_ 500 nm
• Designed for SE-L2 environment
• Non-cryogenic OTA at 280o K
• Thermal control system stabilizes PM temperature
  to 0.1o K
• OTA provides two simultaneously available foci -
  narrow FOV Cassegrain (2 bounce) for Exoplanet
  UV instruments and wide FOV TMA channel for
  Gigapixel imager and MOS
• Designed to permit (but not require) on-orbit
  instrument replacement and propellant
  replenishment (enables a 20 year mission
  lifetime)

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Summary of the ATLAST Concepts
Aperture Size OTA Type Details Ang. Resol. _at_ 500 nm Sensitivity for R5, SNR10 Exoplanet in 100 ksec 3?/D _at_ 500 nm Starlight Suppression Launch Vehicle Guess at Launch Date with 2018 start
8m Monolithic, High areal density ULE glass PM with 7 nm rms surface 15.7 mas 32.0 AB V mag (0.59 nJy) 39 mas 55m - 75m Starshade or Lyot or PIAA coronagraph (w/off-axis SM or arched spider) or VNC Ares V (or similar capacity vehicle) 2028
9.2m Segmented36 x 1.3m AMSD glass, Active WFSC 13.7 mas 32.5 AB V mag (0.38 nJy) 34 mas 55m - 75m Starshade or VNC EELV Delta IV Heavy with 7m fairing 18mT lift 2028
16.8m Segmented36 x 2.4m Actuated Hybrid Mirror, Active WFSC 7.5 mas 33.8 AB V mag (0.11 nJy) 18 mas 70m - 90m Starshade or VNC Ares V (or similar capacity vehicle) 2034
Assumes a 200M technology development program
in 2011-2017
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Starlight Suppression

• Characterizing terrestrial-like exoplanets (lt10
  Mearth) is a prime ATLAST scientific objective.
• Challenge how do we enable a compelling
  terrestrial exoplanet characterization program
  without
• making the optical performance requirements
  technically unachievable for a viable cost (learn
  from TPF-C) and
• seriously compromising other key scientific
  capabilities (e.g., UV throughput).

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Starlight Suppression Options External
Occulter Starshade
ATLAST-9m with 55-m Starshade
2.0 Zodi
2.0 Zodi
2.0 Zodi
0.4 Zodi
Images courtesy of Phil Oakley Web Cash 2008,
2009
Simulations of exosolar planetary systems at a
distance of 10 pc observed with an external
occulter and a telescope with the indicated
aperture size. Planet detection and
characterization become increasingly easier as
telescope aperture increases. The challenges of
deploying and maneuvering the star shade,
however, also increase with increasing telescope
aperture.
ATLAST Starshade Parameters 8m - 9.2m
telescope IWA 58 mas, 55m shade _at_ 80,000
km IWA 40
mas, 75m shade _at_ 155,000 km 16m
telescope IWA 40 mas, 90m shade _at_ 185,000 km
3.0 Zodi
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Starlight Suppression Options Internal
Coronagraphs

• JPLs High-Contrast Imaging (HCI) Test-Bed has
  demonstrated sustained contrast levels of lt 10-9
  using internal, actively corrected coronagraph.
  Require monolithic mirror and, usually, an
  off-axis optical design.
• Segmented optics introduce additional diffracted
  light. Visible Nulling Coronagraph (VNC) can, in
  principle, work with segmented telescope to
  achieve 10-10 contrast. VNC chosen as starlight
  suppression method for TMT as well as for EPIC
  and DAVINCI mission concepts.

Transmission
VNC Sky Transmission Pattern with 64 x 64 DM at
0.68 - 0.88 microns . Credit J. Krist, JPL
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Starlight Suppression Options Monolithic
On-Axis 8-m Telescope
With relay pupil aperture masking, it is possible
to place an internal coronagraph behind each
sub-aperture. Analysis of performance is
TBD. Preliminary dynamic analysis indicates that
the double arch spiders have a 7.5 Hz first mode
versus the conventional 4-arm spider, which has a
10.5 Hz first mode. The double arch spider
meets the Ares V launch requirement.
3m X 6m
3m X 6m
Double-arch Spider for 8-m on-axis telescope
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Large UVOIR telescopes are required for many
other astrophysics research areas
For more info on ATLASThttp//www.stsci.edu/inst
itute/atlast

• Star formation evolution resolved stellar
  populations
• Galaxy formation evolution supermassive black
  hole evolution
• Formation of structure in the universe dark
  matter kinematics
• Origin and nature of objects in the outer solar
  system

A life finder telescope will clearly be a
multi-billion dollar facility - support by a
broad community will be needed if it is to be
built.
ATLAST can characterize a large sample of
potentially habitable worlds AND do a wide range
of pioneering astrophysics.