CHEOPS

CHEOPS (CHaracterizing ExOPlanet Satellite) was proposed as an S-class mission in response to the call for Proposals issued by ESA in March 2012. It has been selected by ESA as the first S-class mission in Cosmic Vision 2015-2025. The mission has been adopted in 2014, and launched on Dec 18 2019.

CHEOPS is a joint ESA-Switzerland project, with important contribution from Italy and nine other ESA Member States (Austria, Belgium, France, Germany, Hungary, Portugal, Spain, Sweden, and the United Kingdom), cooperating within a dedicated Mission Consortium.
It is the first mission dedicated to the characterisation of small-size transiting planets by means of ultrahigh precision photometry on bright stars already known to host planets. It enables an accurate determination of the radii of transiting planets, for which the mass has already been measured from ground-based spectroscopic surveys. It also provides precision radii for new planets discovered by the next generation of ground-based transits surveys (Neptune-size and smaller).
For the first time, CHEOPS enables comparative planetology in an unexplored mass range at a precision never before achieved. CHEOPS data are also fundamental to better select the targets for current facilities, such as the James Webb Space Telescope (JWST), and future ground-based (e.g., ELT) and space-based (e.g., Ariel) missions with spectroscopic capabilities for atmospheric characterisation.

Italy plays a role of primary importance in Cheops, both for the development of the instrument and for its scientific leadership. Researchers from INAF (Astrophysical Observatory of Catania and Astronomical Observatory of Padua) and the University of Padua developed the optical design of the telescope and supported the industry selected by Italian Space Agency (ASI) – a group of companies formed by Leonardo SrL (lead partner), Thales Italia and MediaLario – for the realization of the mirrors, the back-end optics, and for the integration, alignment and test of the telescope. The flight model was delivered by Italy to the Cheops Consortium – led by the University of Bern – in May of 2017.
The INAF team also contributed in an original way to all the scientific preparation phases: writing the scientific requirements, their transposition into technical requirements and their verification; elaboration of the model and analysis of stray light, the requirements of which are very stringent; study of the optical performance of the instrument and eventually contributed to the implementation and validation of data reduction procedures. Furthermore, in collaboration with the University of Padua and with the scientific team of the Cheops consortium, INAF researchers participated in formulating the scientific program for the Guaranteed Time Observing (GTO), which accounts for 80% of the total observing time.

Ongoing Scientific Contribution
Since the start of scientific operations in early 2020, the Italian contribution has remained central to the mission’s success. The INAF researchers from Catania and Padua, together with colleagues from the University of Padua, are deeply involved in the analysis and interpretation of CHEOPS data. They lead several major scientific programs within the Science Team, contributing to the discovery of complex multi-planetary systems, the characterization of “exotic” planetary atmospheres, and the precise measurement of the density of Earth- and Neptune-sized planets. This ongoing work is fundamental to our understanding of the formation and evolution of planetary systems beyond our own.

MISSION SUMMARY

Name: CHEOPS, CHaracterizing ExOPlanet Satellite Primary
Goal: Characterize transiting exoplanets on known bright and nearby host stars
Targets: Known exoplanet host stars with a V-magnitude < = 12 anywhere on the sky
Wavelength: Visible range : 330 to 1100 nm
Telescope: 33 cm reflective on-axis telescope; 19×19 arcmin^2 field of view
Orbit: Sun-synchronous, dusk-dawn orbit at 700 km above Earth
Lifetime: 3.5 years (nominal mission) + 1.5 years (mission extension); currently in its first mission extension until December 2026
Satellite: 1.5 m size; 280 Kg mass
Type: S (small)-class mission

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