Expected precision on planet radii with CHEOPS
The Characterising Exoplanet Satellite (CHEOPS) is the first mission dedicated to search for transits by means of ultra-high-precision photometry on bright stars already known to host planets. One of the most challenging requirements is to reach a 20 parts-per-million (ppm) photometric accuracy over 6 hours, which should allow CHEOPS to detect super-earths transiting very bright stars. The purpose of this talk is to give some highlights on the precision one could expect to achieve on the planet radius, based on the curent knowledge of CHEOPS instrument. I will first quickly present the photometric extraction tool that I’ve used as well as the image simulator CHEOPSim that has been specifically developed for the mission. The transit parameters are computed by fitting a model to the light curve using Gaussian Processes (GP) coupled with Monte Carlo Markov Chains (MCMC). I will present results on the planet radii precision that could be achieved for different scenarii, varying the number of transits, the planet size, the background and the noise level.