ATLAST: Advanced Technology LargeAperture Space Telescope

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

• Marc Postman
• STScI

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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 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 space telescope required to answer
  this fundamental question?
• Habitable Zones (HZ) of nearby stars subtend very
  small angles (
• Earth-mass planets within these HZ will be very
  faint ( 28.5 AB mag).
• Number of very nearby stars capable of hosting
  potentially habitable planets is not large (e.g.,
  non-binary, solar-type or later (F,G,K)).
• Habitable planets with detectable biosignatures
  may be rare. We may need to search many systems
  to find even a handful.

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Exoplanet Characterization Are there
life-bearing worlds?
Carbon Dioxide
Methane
Large Space Telescopes
Water
Molecular Oxygen
Ozone
Very Large Space Interferometers

• For Direct Spectroscopy and Photometry need high
  angular resolution to resolve the HZ in nearby
  star systems at wavelengths of biomarkers
• Angular resolution scales as ?/D. Furthermore,
  technical limitations suggest you will want most
  of the HZ to lie outside of 3 ?/D
• 1 AU at 10 pc is 100 mas. Solar system HZ 0.85
  - 1.25 AU.

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Exoplanet Characterization Are there
life-bearing worlds?

• Earth at 10 pc 29.1 AB mag (8.3 nJy)
• Earth at 20 pc 30.6 AB mag (2.1 nJy)
• Sensitivity scales with aperture as D1.8 - 4
  depending on exo-zodi level and on method used to
  suppress starlight.
• Need telescope with nJy sensitivity to
• obtain S/N10 low resolution (R100) spectroscopy
  to identify key habitability and bio-signatures
  in the range 0.3 - 2.5 microns in
• Obtain S/N20 broadband photometry on timescales
  less than one planetary rotation period (to
  enable studies of temporal variation on diurnal
  timescales)

A S/N10 spectrum (R70) of Earth-like planet
orbiting a solar luminosity star at a distance of
20 pc (V30.6 AB mag). The required exposure
time is 150 hours with an 8-m space telescope
20 hours with a 16-m space telescope.
Habitability and bio-signatures are shown.
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Detecting Weather and Surface Features
Ford et al. 2003 Model of broadband photometric
temporal variability of Earth
Require S/N 20 (5 photometry) to detect
Earth-like temporal variations in reflectivity.
We would need to achieve a single observation at
this S/N in to enable measurements the variability consisting
of at least 4 independent observations per
rotation period.
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Exoplanet Characterization Are there
life-bearing worlds?

• How big a space telescope is required to detect
  at least 10 terrestrial exoplanets with
  biosignatures (assuming low exo-zodi levels)?
• NBio Nstars ?Earth pL
• NBio number of stars with at least 1 planet in
  HZ that has detectable biosignature with S/N 10
  in 100 ksec of exposure time
• Nstars number of stars whose HZ is resolved by
  a telescope of aperture DTel
• Nstars? (DTel )2.5 (c.f. Beckwith 2008)
• ?Earth fraction of those stars that have
  terrestrial planets in the HZ
• pL probability that at least one of those HZ
  planets has detectable biosignatures.

Number of Stars with resolved HZ as a function of
Telescope Aperture
If ??earth . pL 1 then DTel
4m ???????earth . pL 8m ???????earth . pL
NBio 10 0.5 (DTel )2.5.?Earth?. pL
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An optical/NIR space telescope with a filled
aperture of at least 8-meters will probably be
required to definitively answer the question Are
we alone?
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Studying two architectures 8-m monolithic and
(10-m, 16-m) segmented telescope designed for
Sun-Earth L2 orbit operations

• Monolithic Primary
• On and off-axis secondary mirror concepts being
  investigated.
• Off-axis concept optimal for exoplanet
  observations with internal coronagraph. But adds
  complexity to packaging and WFSC.
• Uses existing ground-based mirror materials. This
  is enabled by large lift capacity of Ares V cargo
  launch vehicle (60 mT).
• Massive mirror (20 mT) has 7 nm rms surface.
  Total observatory mass 36 mT.

• Segmented Primary
• Only studying designs with an on-axis secondary.
• Requires use of lightweight mirror materials
  fabrication
• 16-m observatory has total mass 45 mT, within
  capacity of Ares V.
• 10-m observatory can fly in advanced ELV. Does
  not require Ares V.
• Requires active WFSC systems and solar torque
  mitigation.

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Studying two architectures 8-m monolithic and
(10-m, 16-m) segmented telescope
A monolithic 8-m or segmented 16-m optical space
telescope requires an Ares V fairing.
A segmented 10-m optical space telescope can be
used with enhanced but existing ELV.
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Non-cryogenic optics operated at 280 deg K.
Diffraction-limited at 500 nm.
Wide-field instruments at TMA focii. Up to 12
arcmin FOV on 8-meter 5 arcmin on 16-meter
On-axis instruments (e.g., exoplanet imager
spectrometer) at Cass focus. Narrow FOV (arcsec). Minimize reflections for high-throughput
UV instrument at Cass.
Primary secondary have coated Aluminum surfaces
to enable sensitivity down to a wavelength of 110
nm. TMA optics and optics internal to instruments
can be coated differently to optimize efficiency.
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Technology Development Needed in Coming Decade
Relevant to Life Detection

• 8m Monolithic Telescope
• High-contrast (10-10) starlight suppression
• Internal Coronagraph
• External Occulter
• Active observatory wavefront control system
• Ultra-low or zero noise photon counting detectors
• Solar torque mitigation and 2 mas roll and
  attitude control
• Ares V Cargo Launch Vehicle (enabling technology
  for full circular aperture (or 6 x 8m ellipse)
  and cost control less complexity)

• 10m to 16m Segmented Aperture Telescope
• High-contrast (10-10) starlight suppression
• Vis. Nulling Coronagraph
• External Occulter
• Active observatory wavefront control system
• Ultra-low or zero noise photon counting detectors
• Solar torque mitigation and 1 mas roll and
  attitude control
• Ares V Cargo Launch Vehicle (for 16m).
• Light-weight mirror materials and manufacturing
  (
• Deployable light baffle

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Two closing thoughts
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Cost does NOT follow a fixed scaling relation
with aperture as technology or architecture
advance
HST
JWST
ATLAST
Herschel
EELT
D1.4
TMT
Spitzer
Kepler
Subaru
Keck
LBT
VLT
Hale 5m
GALEX
Mayall 4m
SOAR
SALT
WIYN
HET
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Large UVOIR telescopes are required for many
other astrophysics research areas

• 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 - and support by a
broad community will be needed if it is to be
built.