The CHEOPS mission
Experimental Astronomy, vol. 51, pp. 109–151
Abstract
Abstract The CHaracterising ExOPlanet Satellite (CHEOPS) was selected on October 19, 2012, as the first small mission (S-mission) in the ESA Science Programme and successfully launched on December 18, 2019, as a secondary passenger on a Soyuz-Fregat rocket from Kourou, French Guiana. CHEOPS is a partnership between ESA and Switzerland with important contributions by ten additional ESA Member States. CHEOPS is the first mission dedicated to search for transits of exoplanets using ultrahigh precision photometry on bright stars already known to host planets. As a follow-up mission, CHEOPS is mainly dedicated to improving, whenever possible, existing radii measurements or provide first accurate measurements for a subset of those planets for which the mass has already been estimated from ground-based spectroscopic surveys. The expected photometric precision will also allow CHEOPS to go beyond measuring only transits and to follow phase curves or to search for exo-moons, for example. Finally, by unveiling transiting exoplanets with high potential for in-depth characterisation, CHEOPS will also provide prime targets for future instruments suited to the spectroscopic characterisation of exoplanetary atmospheres. To reach its science objectives, requirements on the photometric precision and stability have been derived for stars with magnitudes ranging from 6 to 12 in the V band. In particular, CHEOPS shall be able to detect Earth-size planets transiting G5 dwarf stars (stellar radius of 0.9 R ⊙ ) in the magnitude range 6 ≤ V ≤ 9 by achieving a photometric precision of 20 ppm in 6 hours of integration time. In the case of K-type stars (stellar radius of 0.7 R ⊙ ) of magnitude in the range 9 ≤ V ≤ 12, CHEOPS shall be able to detect transiting Neptune-size planets achieving a photometric precision of 85 ppm in 3 hours of integration time. This precision has to be maintained over continuous periods of observation for up to 48 hours. This precision and stability will be achieved by using a single, frame-transfer, back-illuminated CCD detector at the focal plane assembly of a 33.5 cm diameter, on-axis Ritchey-Chrétien telescope. The nearly 275 kg spacecraft is nadir-locked, with a pointing accuracy of about 1 arcsec rms, and will allow for at least 1 Gbit/day downlink. The sun-synchronous dusk-dawn orbit at 700 km altitude enables having the Sun permanently on the backside of the spacecraft thus minimising Earth stray light. A mission duration of 3.5 years in orbit is foreseen to enable the execution of the science programme. During this period, 20% of the observing time is available to the wider community through yearly ESA call for proposals, as well as through discretionary time approved by ESA’s Director of Science. At the time of this writing, CHEOPS commissioning has been completed and CHEOPS has been shown to fulfill all its requirements. The mission has now started the execution of its science programme.
Authors 21
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Affiliation as printed
Observatoire de Genève, University of Geneva, Geneva, Switzerland
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Consejo Superior de Investigaciones Científicas · Centro de Astrobiología
Affiliation as printed
Unidad de Excelencia María de Maeztu - Centro de Astrobiología (INTA-CSIC), Madrid, Spain
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Austrian Academy of Sciences · Space Research Institute
Affiliation as printed
Space Research Institute, Austrian Academy of Sciences, Graz, Austria
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Osservatorio Astronomico di Padova · National Institute for Astrophysics
Affiliation as printed
INAF Astronomical Observatory of Padova, Padova, Italy
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Osservatorio Astronomico di Padova · National Institute for Astrophysics
Affiliation as printed
INAF Astronomical Observatory of Padova, Padova, Italy
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Institut de Planétologie et d'Astrophysique de Grenoble · Université Grenoble Alpes
Affiliation as printed
Institut de Planétologie et d’Astrophysique, University of Grenoble, Grenoble, France
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University of Bern · Center for Space and Habitability
Affiliation as printed
Center for Space and Habitability, University of Bern, Bern, Switzerland
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Malcolm C. Fridlund Aachen
Leiden University · Chalmers University of Technology
Affiliation as printed
Chalmers University, Göteborg, Sweden
University of Leiden, Leiden, The Netherlands
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Affiliation as printed
Zentrum für Astronomie und Astrophysik, Technische Universität Berlin, Berlin, Germany
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Centre National de la Recherche Scientifique · Aix-Marseille Université
Affiliation as printed
Aix Marseille Univ, CNRS, CNES, LAM, Marseille, France
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Affiliation as printed
Observatoire de Genève, University of Geneva, Geneva, Switzerland
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Centre National de la Recherche Scientifique · Université Paris Sciences et Lettres · Observatoire de Paris · Sorbonne Université · Institut de Mécanique Céleste et de Calcul des Éphémérides
Affiliation as printed
IMCCE, CNRS, Observatoire de Paris, PSL University, Sorbonne Université, Paris, France
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Institut d'Astrophysique de Paris
Affiliation as printed
Institut d’Astrophysique de Paris, Paris, France
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Affiliation as printed
Observatoire de Genève, University of Geneva, Geneva, Switzerland
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Osservatorio Astronomico di Padova · National Institute for Astrophysics
Affiliation as printed
INAF Astronomical Observatory of Padova, Padova, Italy
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Affiliation as printed
Department of Physics and Astronomy, University of Padova, Padova, Italy
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Affiliation as printed
Department of Astrophysics, University of Vienna, Vienna, Austria
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University of Padua · Osservatorio Astronomico di Padova · National Institute for Astrophysics
Affiliation as printed
Department of Physics and Astronomy, University of Padova, Padova, Italy
INAF Astronomical Observatory of Padova, Padova, Italy
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Institute of Space Sciences · Institut d'Estudis Espacials de Catalunya
Affiliation as printed
Institut de Ciènces de l’Espai (ICE, CSIC), Campus UAB, Bellaterra, Spain
Institut d’Estudis Espacials de Catalunya (IEEC), Barcelona, Spain
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Osservatorio Astrofisico di Catania · National Institute for Astrophysics
Affiliation as printed
INAF Astrophysical Observatory of Catania, Catania, Italy
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Affiliation as printed
Observatoire de Genève, University of Geneva, Geneva, Switzerland
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