Report from NASA’s ExoPAG ( E xoplanet E xploration P rogram A nalysis G roup)

1. Report from NASA’s ExoPAG(Exoplanet Exploration Program Analysis Group) James Kasting ExoPAG Chair

2. What is the ExoPAG? D. Hudgins, April, 2009 The ExoPAG is designed be an open, community-based forum for soliciting and coordinating community input into the development and execution of NASA’s Exoplanet Exploration Program (ExEP). To carry out its role, the ExoPAG will: • Conduct analyses of ExEP planning and activities under auspices of NAC; • Provide science and technology inputs to the Astrophysics Subcommittee (APS) for propagation to the Agency through the NASA advisory structure • Evaluate capabilities of potential missions w/r/t ExEP science goals; • Regularly review ExEP goals, objectives, investigations and required measurements against the current state-of-the-art, drawing on the widest possible community input; • Articulate and prioritize focus areas for technology development; and • Provide recommendations on related activities such as ground-based observing, theory and modeling programs, and community engagement. • Provide a forum for maintaining regular, unfettered communication with program stakeholders in government, academia, and industry.

3. What is the ExoPAG? D. Hudgins, April, 2009 Structure and function of the ExoPAG: • Chair appointed from APS membership (J. Kasting); • Chair supported by Executive Secretary (HQ ExEP PS, D. Hudgins) and Executive Committee; • nominations solicited through open “Dear Colleague” letter to community • members serve rolling 3-year terms • constituted to achieve functional balance between observers, theorists, and technologists, as well as scientific balance across fields of astrophysics, (exo)planetary science, and astrobiology; • Meetings held biannually with schedule set by Chair in consultation with EC; • Tasking from SMD, NAC Science Committee, or Astrophysics Subcommittee • Results of ExoPAG meetings and analyses reported to the Astrophysics Subcommittee

4. Current ExoPAG Steering Committee members Tom Greene (Ames)—coronagraphs/JWST Dave Bennett (Notre Dame)--gravitational microlensing Charlie Noecker (JPL)--everything, including technology Dan Coulter (JPL)—technology/coronagraphs Bruce Macintosh (Lawrence Livermore)--Ground-based AO/direct imaging Brad Hansen (UCLA)--theory and measurements Lisa Kaltenegger (Max Planck Institute)—interferometry/astrobiology Alycia Weinberger (Carnegie Inst.)--circumstellar disks/astrometry Aki Roberge (Goddard)—debris disks/zodiacal dust/New Worlds Observer

5. ExoPAG activities • 5 meetings held since January, 2010 • ExoPAG5 held this past weekend • Roughly 40-80 participants at each meeting • Two joint meetings with COPAG, described further below • Study Analysis Groups (SAGs) set up • Direct imaging flagship mission requirements • Exozodiacal dust studies

6. Main focus to this point • Planning for a future, flagship-class, direct imaging mission to find and characterize other Earth-like planets • Technology development for such a New Worlds/New Horizons mission was a high-priority recommendation of the Astro2010 Decadal Survey

7. TPF-C TPF-I/Darwin • There are at least three concepts • for a large, space-based tele- • scope that could directly image • Earth-size planets around other • stars • These missions would also look for • spectroscopic biomarkers (O2, O3, CH4) • and try to infer the presence or absence • of lifeon such planets • The ExoPAG is hoping to help NASA • decide how to choose between these • mission concepts TPF-O NASA’s Terrestrial Planet Finder concepts

8. Collaboration with COPAG • COPAG is also interested in large, UV/optical space telescopes • Some in that community are thinking really big (8-16 m aperture) • But see below.. • Question: Are UV-capable coatings compatible with a TPF-like direct imaging mission? 16-m version of the proposed ATLAST space telescope (M. Postman, STScI)

9. Flagship mission requirements SAG • A fairly complete set of science requirements for a direct imaging mission was developed for the 2005 version of TPF-C • Is the same set of requirements applicable to an occulter mission? • No.. • How does the mission design depend on Earth and exozodi brightness? TPF-C (internal coronagraph) – mission concept circa 2005

10. Earth • Astronomers describe planetary habitability in terms of a factor called Earth—the fraction of stars that have at least one planet in their habitable zone • This is what we need to know in order to design a space telescope to look for such planets around nearby stars

11. Kepler Mission • This space-based telescope • will point at a patch of the • Milky Way and monitor the • brightness of ~160,000 stars, • looking for transits of Earth- • sized (and other) planets • 105 precision photometry • 0.95-m aperture capable • of detecting Earths • Launched: March 5, 2009 http://www.nmm.ac.uk/uploads/jpg/kepler.jpg

12. Measuring exozodi brightness • The other key parameter for designing a TPF telescope is the exozodi brightness • High brightness  need a larger telescope to distinguish the planet from the dust • LBTI (the Large Binary Telescope Interfero-meter) is the key instrument for measuring this background Habitable zone Exozodi detection levels for various ground- and space-based platforms (Courtesy: Aki Roberge. Available in upcoming SAG1 report.)

13. Smaller probe-class missions • A key concern, given the current (bleak) budget environment, is that there may not be enough money for a flagship mission in the 2020-2030 time frame • Consequently, the ExoPAG is also studying probe-class missions (<$1B and $1B-$2B) • We heard talks from 3 proposed Explorer missions at ExoPAG5 this past weekend • TESS—Transiting Exoplanet Survey Satellite • FINESSE—Fast INfrared Exoplanet Spectroscopy Survey Explorer • EXCEDE—Exoplanetary Circumstellar Environments and Disk Explorer (technology development only)

14. Conclusions • Characterizing planets in the habitable zonesof nearby stars requires a large, space-based direct imaging mission • This remains the top priority for ExoPAG • SAG reports on flagship mission requirements and exozodi dust levels will be available soon • Collaboration with other interest groups (e.g., COPAG) is being actively encouraged • Smaller probe-class exoplanet missions are also of interest and may have to sustain us in the near term • We welcome comments and participation from all members of the astronomical community