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

Astrophysics Division What is the ExoPAG? 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. D. Hudgins, April, 2009

Astrophysics Division What is the ExoPAG? 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 D. Hudgins, April, 2009

Current ExoPAG Steering Committee members 1.Tom Greene (Ames)—coronagraphs/JWST 2.Dave Bennett (Notre Dame)--gravitational microlensing 3.Charlie Noecker (JPL)--everything, including technology 4.Dan Coulter (JPL)—technology/coronagraphs 5.Bruce Macintosh (Lawrence Livermore)--Ground-based AO/direct imaging 6.Brad Hansen (UCLA)--theory and measurements 7.Lisa Kaltenegger (Max Planck Institute)— interferometry/astrobiology 8.Alycia Weinberger (Carnegie Inst.)--circumstellar disks/astrometry 9.Aki Roberge (Goddard)—debris disks/zodiacal dust/New Worlds Observer

ExoPAG activities 5 meetings held since January, 2010 –ExoPAG5 held this past weekend –Roughly participants at each meeting Two joint meetings with COPAG, described further below Study Analysis Groups (SAGs) set up 1.Direct imaging flagship mission requirements 2.Exozodiacal dust studies

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

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 (O 2, O 3, CH 4 ) and try to infer the presence or absence of life on such planets The ExoPAG is hoping to help NASA decide how to choose between these mission concepts TPF-I/Darwin TPF-C TPF-O NASA’s Terrestrial Planet Finder concepts

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)

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

 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

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

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 Exozodi detection levels for various ground- and space-based platforms (Courtesy: Aki Roberge. Available in upcoming SAG1 report.) Habitable zone

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 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 1.TESS—Transiting Exoplanet Survey Satellite 2.FINESSE—Fast INfrared Exoplanet Spectroscopy Survey Explorer 3.EXCEDE—Exoplanetary Circumstellar Environments and Disk Explorer (technology development only)

Conclusions Characterizing planets in the habitable zones of 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