CHEOPS: A transit photometry mission for ESA's small mission programme

Abstract

Abstract. Ground based radial velocity (RV) searches continue to discover exoplanets below Neptune mass down to Earth mass. Furthermore, ground based transit searches now reach milli-mag photometric precision and can discover Neptune size planets around bright stars. These searches will find exoplanets around bright stars anywhere on the sky, their discoveries representing prime science targets for further study due to the proximity and brightness of their host stars. A mission for transit follow-up measurements of these prime targets is currently lacking. The first ESA S-class mission CHEOPS (CHaracterizing ExoPlanet Satellite) will fill this gap. It will perform ultra-high precision photometric monitoring of selected bright target stars almost anywhere on the sky with sufficient precision to detect Earth sized transits. It will be able to detect transits of RV-planets by photometric monitoring if the geometric configuration results in a transit. For Hot Neptunes discovered from the ground, CHEOPS will be able to improve the transit light curve so that the radius can be determined precisely. Because of the host stars' brightness, high precision RV measurements will be possible for all targets. All planets observed in transit by CHEOPS will be validated and their masses will be known. This will provide valuable data for constraining the mass-radius relation of exoplanets, especially in the Neptune-mass regime. During the planned 3.5 year mission, about 500 targets will be observed. There will be 20% of open time available for the community to develop new science programmes. a

The SOPHIE search for northern extrasolar planets

“…The actual number of planets with precise density measurements is indeed far too low to cover the parameter space and constrain interior, formation, or evolution models for the low-mass planet population. The future transit search missions around bright stars TESS (Ricker et al 2014) and CHEOPS (Broeg et al 2013;Fortier et al 2014) will address this issue from two complementary perspectives. While TESS will substantially increase the number of transiting exoplanets suitable for high-precision RV measurement, CHEOPS will mesure precise radii of known exoplanets that have been discovered with radial velocities to derive precise densities.…”

“…Detection and characterization of new low-mass exoplanets orbiting bright stars is motivated by the need to obtain accurate measurements of the projected mass and the eccentricity and to identify all the components of multiple systems to constrain models of exoplanet evolution. Such exoplanets orbiting bright stars will also be key targets for a deeper and more extended characterization with CHEOPS (Broeg et al 2013;Fortier et al 2014), for instance, which searches for the transit, and JWST (Beichman et al 2014), which searches for atmospheric signatures.…”

Constraining the volatile fraction of planets from transit observations

“…Before this date, CHEOPS (Broeg et al 2013) and TESS (Ricker et al 2010) will provide many transit observations. These observations, however, are less usable in the framework of what is described in this paper, for two reasons.…”

“…Future transit missions may be able to measure this effect. Transit observations such as will be performed by CHEOPS (Broeg et al 2013), TESS (Ricker et al 2010) or PLATO (Rauer et al 2014), will be able to set statistical constraints on planetary composition with this model, provided the stellar age is known with sufficient accuracy and enough planets can be observed with sufficient mass and radius accuracy.…”

EChOSim: The Exoplanet Characterisation Observatory software simulator

“…Also growing rapidly is the list of confirmed exoplanets, which currently exceeds 1,000 exoplanetary systems hosting nearly 2,000 planets. Ongoing and planned ESA and NASA missions form space such as GAIA [1], Cheops [2], PLATO [3], Euclid [4], Kepler II [5] and TESS [6] will increase the number of known systems to tens of thousands. Ground-based surveys using a variety of direct and indirect techniques will contribute further.…”