American Astronautical Society, Astronauts and Robots: Partners in Space Exploration, May 12-13, 2015 - http://astronautical.org/event/astronauts-robots
2. Exoplanet Exploration Program
Purpose described in
2014 NASA Science Plan
1. Discovering planets around other stars
2. Characterizing their properties
3. Identifying candidates that could
harbor life
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4. Jet Propulsion Laboratory
California Institute of Technology
Hubble
Spitzer
Kepler
JWST
TESS
Missions
New Worlds
Telescope
What Exoplanet Direct Imaging
missions are possible for
Probe-Scale ($1B)?
Habitable Exoplanet Imager
(HabEx)
(L-UV-OIR)
WFIRST /
AFTA
5. Exo-S:
External Occulter
(Starshade)
S. Seager,
STDT Chair, MIT
High-Contrast Imaging
Probe-Scale studies
Exo-C:
Internal Occulter
(Coronagraph)
K. Stapelfeldt,
STDT Chair, GSFC
Ground rules:
• Compelling Science beyond
ground capability at time of
mission
• $1B LCC confirmed by Aerospace
CATE
• Launch 2024
• TRL 5 by end of Phase A, TRL 6
by end of Phase B
Purpose
• Alternatives for 2017 new start
• Motivate technology investments
• Candidates for next Decadal
Survey
7. Exo-C: Internal Coronagraph
• Visible Hybrid Lyot Coronagraph mask
• Design Reference Mission observes > 400
unique targets
– Spectra or colors for 30 planets
– Access to a few super-Earths in HZ of their stars.
• 1.4m aperture
• Cost: $1B life-cycle, validated by Aerospace
CATE
• 3 year mission, Earth trailing orbit
• Exo-C’s scope, hardware, and expected cost
are very similar to those of NASA’s Kepler
mission
• A modest aperture can be very effective
if coronagraphy requirements allowed to
drive the mission and telescope design
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Planet discovery - Altair
RV planet spectrum - Eridani b
Optimal
Design
9. Exo-S Mission Concepts
Dedicated (Co-Launched) Mission
• Telescope: 1.1 m
• Retargeting: by the telescope s/c (SEP)
• $1.1B lifecycle cost
Rendezvous Mission
• Telescope: WFIRST/AFTA 2.4 m is adopted
• Orbit: Earth-Sun L2
• Retargeting: by the starshade spacecraft
• Minimal impact to telescope to be “starshade ready”
• $0.6B lifecycle cost
Common to both:
• Starshade design (30 m vs. 34 m diameter)
• Formation-flying over ~35,000 km separation
• 3 Year Mission
• Science:
• Spectra or colors for 30 planets.
• Access to several Earths in HZ of their stars
10. WFIRST / AFTA Coronagraph
Direct Imaging of our Nearest Exoplanet Neighbors
Coronagraph Instrument
― Imaging and spectral channels
― 0.4 – 1 μm bandpass
― ≤ 10-9 detection contrast
― 100 mas inner working angle at 0.4 μm
― R ~ 70
Coronagraph Science
― Imaging and spectroscopy of exoplanet
atmospheres down to a few Earth
masses
― Study populations of debris disks
Coronagraph will develop the technologies for New Worlds Telescope mission
No Mask With Mask
With Mask and
Deformable Mirrors
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11. Take Away Messages
• Kepler showed us that the Milky Way Galaxy is abundant
with exoplanets
• Direct Imaging is a logical next step
• Systematic approach to science, design, technology and
cost yields compelling probe-scale direct imaging
missions
• Optimized telescopes permit smaller diameter mirrors for
similar exoplanet yields
• An exoplanet biosignature detection would be among the
greatest science discoveries of all time
Exep.jpl.nasa.gov
The NASA Program office is at JPL
Much smaller than MEP, but I submit if you count planets, great growth potential!
Last point: habitable planets, size, location, evidence of water, biosignature gases out of equilibrium
Even though it will be a long time…
Kepler showed an abundance – as many as one for every star in the Milky Way
You can buy these postcards now
Beyond Kepler, TESS / JWST for transit spectroscopy
Governed by decadal survey: recommended WFIRST, and a technology program for NWT for direct imaging
NWT is one of large missions considered for next decadal – two among them consider exoplanets
WSIC: cost and technical feasibility will matter for NWT/next decadal, we found solutions, and les
A small aperture can be very effective if coronagraphy/exoplanet requirements can drive the mission design
Radial velocity and transit surveys have shown exoplanets are abundant. Spectral characterization is the natural next step; reflected light planets are unique targets.
2nd and 3rd purposes remain
Charged – two STDTs, with two different but coordinated design teams. 1.75 years.
What did the teams come up with?
10-10 post processing optical contrast with 20% bandwidth as close as 3 /D already achieved in the Laboratory.
Message:
A starshade mission is comprised of two spacecraft - one is the starshade itself and the other is a conventional telescope. The starshade, tens of meters in diameter, first deploys into a flower-like structure and then the inner disk deploys into the final extended configuration. The starshade and telescope move to an Earth-leading orbit with the starshade about 40,000 km in front of the telescope. L2 is also an option. The starshade both blocks the light from the star and directs diffraction away from the telescope, revealing planets that may be orbiting it. The lateral formation flying requirement is about 2 m in diameter and is maintained with small thrusts about every 100 seconds.
Details:
The starshade rotates slowly around its axis of symmetry for reasons of thermal homogeneity and imperfections.
Mass of starshade alone is about 800 kg; starshade plus spacecraft is about 1100 kg.
Flight petals are about 7m and flight inner rim is about 20m
Primary mirror is 1.1m
Points to make:
The existing coronagraph instrument performs both science and formation guidance functions without adding focal planes.
Many more mission options, these are chosen due to cost constraints
STDT chose to study the Rendezvous mission
WFIRST/AFTA + Starshade
simulated image of
Beta Canum Venaticorum
8.44 pc, G05
plus solar system planets
AFTA’s coronagraph will develop the technologies for a future exo-Earth mission. To do the HCI science, must control that diffraction pattern from the star – first using masks/stops in pupil/focal plane, and then further cleaning up wavefront with WFSCC, DMs, and post-processing. 10-8 raw, 10-9 post-processed. See the planet.