ESA/SRE(2013)5 December 2013 PLATO Revealing habitable worlds around solar-like stars Assessment Study Report European Space Agency PLATO Assessment Study Report page 2 The front page shows an artist’s impression of planetary systems viewed by PLATO (©DLR). PLATO Assessment Study Report page 3 PLATO Assessment Study – Mission Summary Key scientific Detection of terrestrial exoplanets in the habitable zone of solar-type stars and characterisation of goals their bulk properties needed to determine their habitability. Characterisation of thousands of rocky (including Earth twins), icy or giant planets, including the architecture of their planetary system, to fundamentally enhance our understanding of the formation and the evolution of planetary systems. These goals will be achieved through: 1) planet detection and radius determination (2% precision) from photometric transits; 2) determination of planet masses (better than 10% precision) from ground-based radial velocity follow-up, 3) determination of accurate stellar masses, radii, and ages (10% precision) from asteroseismology, and 4) identification of bright targets for atmospheric spectroscopy. Observational Ultra-high precision, long (up to several years), uninterrupted photometric monitoring in the concept visible band of very large samples of bright (mV ≤11) stars. Primary data Very accurate optical light curves of large numbers of bright stars. product Payload Payload • Set of 32 normal cameras organised in 4 groups resulting in many wide-field co-aligned concept telescopes, each telescope with its own CCD-based focal plane array; • Set of 2 fast cameras for bright stars, colour requirements, and fine guidance and navigation. Optical system 6 lenses per telescope (1 aspheric) Focal planes 136 CCDs (4 CCDs per camera) with 4510 4510 18 µm pixels Instantaneous ∼ 2250 deg2 field of view Overall mission profile Observing plan Two long monitoring phases (two years each) single field monitored. Two years additional "step-and-stare" phase with several successive fields monitored for a few months each. Duty cycle ≥ 95% Launcher Launch by Soyuz-Fregat2-1b from Kourou in 2022/2024 Orbit Transfer to L2, then large amplitude libration orbit around L2 Description of Spacecraft Stabilisation 3-axis Telemetry X-band (10 MHz maximum bandwidth) band Average 109 Gb per day downlink (Assumption: ground station contact for 4 hours per day, 3.5 hours for data downlink with a capacity rate of 8.7 Mbps) Pointing 0.2 arcsec rms over 14 hours stability Pointing A 90° rotation around the line of sight every 3 months strategy PLATO Assessment Study Report page 4 … for had we never seen the stars, and the sun, and the heaven, none of the words which we have spoken about the universe would ever have been uttered. But now the sight of day and night, and the months and the revolutions of the years, have created number, and have given us a conception of time, and the power of enquiring about the nature of the universe… Plato, in Timaeus Foreword The PLATO mission was proposed in 2007 as a medium class candidate in response to the first call for missions of the Cosmic Vision 2015-2025 program for a launch in 2017–2018. The proposal was submitted by Dr. Claude Catala (Observatoire de Paris) on behalf of a large consortium of scientists from laboratories all across Europe. Following favourable reviews by ESA’s scientific Advisory structure, PLATO was selected in 2007 as one of the missions for which an ESA assessment study was carried out in 2008 and 2009. The PLATO mission was subsequently selected for a definition study, starting in February 2010. The definition study involved two concurrent industrial contracts for the definition of the mission profile, the satellite, and parts of the payload module. The PLATO Mission Consortium, involving more than 350 scientists and engineers in virtually all ESA Member States, as well as a few members from the US and Brazil, carried out the study of the instrument and their contributions to the science ground segment. A specific industrial contract for the study of the CCDs procurement was issued by ESA. Following the non-selection of PLATO in October 2011 for the M1 or M2 launch opportunities, the ESA Science Programme Committee endorsed the solicitation of a proposal to the PLATO Mission Consortium to be a candidate for the M3 launch opportunity in 2022–2024. This had considered the positive recommendation by ESA’s Advisory structure concerning the PLATO mission scientific competitiveness with the missions selected in response to the Cosmic Vision 2010 Call (the “M3 candidates”). The PLATO Mission Consortium responded with a proposal for the provision of the payload and science ground segment components formulated in the M3 mission framework. A major change was the transfer of the lead activities from France to Germany, with Prof. Heike Rauer (DLR) as new PLATO Mission Consortium lead. Subsequent to ESA’s review, PLATO has been a candidate for the M3 launch opportunity since March 2013. Whereas the technical solution for the spacecraft, payload and operations has remained unchanged, the organisational, programmatic and cost aspects of the mission have been updated taking into account the M3 reference schedule. The science case for the mission has been significantly reworked and elaborated, to account for the large developments in exoplanetology and asteroseismology of the last two years, and to describe the high relevance of PLATO in the scientific context of the next decade. This report describes the outcome of the current assessment study, which is based on the definition study carried out in 2010 and 2011. It covers the scientific, technical, and as well as managerial aspects. This report results from a vast team effort, involving several parties (ESA, the PLATO Mission Consortium, Astrium/EADS, and Thales Alenia Space) under the general supervision by the PLATO Science Study Team and the ESA Study Team. The PLATO Study Team PLATO Assessment Study Report page 5 Authorship, acknowledgements This report was prepared by: ESA Science Study Team (SST) Name Affiliation City, Country Heike Rauer Inst. of Planetary Research, DLR Berlin, Germany Don Pollacco University of Warwick Coventry, UK Marie-Jo Goupil Observatoire de Paris-Meudon Paris, France Giampaolo Piotto Università di Padova Padova, Italy Stéphane Udry Université de Genève Genève, Switzerland PLATO Study Data Processing Manager Laurent Gizon MPI for Solar System Research Göttingen, Germany The ESA Team supporting the activities is composed by: ESA Study Team Philippe Gondoin ESA Noordwjik, The Netherlands Osvaldo Piersanti (Study Managers) Ana M. Heras ESA Noordwjik, The Netherlands Malcolm Fridlund (Study Scientists) Anamarija Stankov (Payload Manager) ESA Noordwjik, The Netherlands Mark Baldesarra (System Engineer) ESA Noordwjik, The Netherlands Laurence O’Rourke (Science Ops) ESA Madrid, Spain ESA Coordinator Arvind Parmar ESA Noordwjik, The Netherlands Contributions to this Assessment Study have been made by the PLATO Team, and part of its text has been submitted to Experimental Astronomy (arXiv:1310.0696). Contributors to these activities are acknowledged in the Annex. The PLATO Team gratefully thanks William J. Borucki, Kepler PI, for his letter of support (link to letter). PLATO Assessment Study Report page 6 Table of contents 1 EXECUTIVE SUMMARY ........................................................................................................ 9 2 SCIENTIFIC OBJECTIVES .................................................................................................. 12 2.1 Science Goals I: Planetary Science ................................................................................................. 12 2.1.1 Planet detection and characterisation of bulk parameters ........................................................... 12 2.1.2 Constraints on planet formation from statistics .......................................................................... 16 2.1.3 Terrestrial planets ....................................................................................................................... 19 2.1.4 Gas giants and icy planets ........................................................................................................... 21 2.1.5 Planets around Sub-giant and Giant Stars ................................................................................... 24 2.1.6 Planets around post-RGB stars ................................................................................................... 24 2.1.7 Circumbinary planets .................................................................................................................. 25 2.1.8 Evolution of planetary systems ................................................................................................... 26 2.1.9 Planetary atmospheres ................................................................................................................ 27 2.1.10 Characterising stellar-exoplanet environments ........................................................................... 29 2.1.11 Detection of rings, moons, Trojans and comets .......................................................................... 29 2.2 Science Goals II: Probing stellar structure and evolution by asteroseismology ............................. 30 2.2.1 Stellar parameters as key to exoplanet parameter accuracy ........................................................ 31 2.2.2 Stellar models and evolution......................................................................................................