The PLATO mission fine guidance system

Kurzfassung

PLATO - PLAnetary Transits and Oscillation of stars - is a the third medium-class mission in the European Space Agency (ESA) Cosmic Vision programme, whose launch is foreseen by 2026. The objective is the detection and characterization of terrestrial exoplanets up to the habitable zone of solar-type stars by means of their transit signature in front of a very large sample of bright stars. In addition to the planet detection, PLATO will measure seismic oscillations of a large sample of stars, including those orbited by planets, in order to make progress in stellar physics and to understand the properties of the exoplanet systems. The PLATO payload consists of an instrument with 26 cameras: 24 "normal" cameras with a cadence of 25s and two "fast" cameras with a cadence of 2.5s. The fast cameras will provide scientific observation of bright stars with unprecedented photometric precision and temporal resolution. But these cameras serve also as redundant Fine Guidance System (FGS) and will be an integral part of the Attitude and Orbit Control System (AOCS) of the satellite. Their goal is to ensures a very high pointing precision, which is required to achieve a high photometric precision with the full payload. Working as a star-tracker, the attitude calculation is based on guide star positions on the focal plane and their reference directions given by a star catalogue. Compared to predecessor missions like CoRoT, Kepler, or TESS, the precision of the fine guidance algorithm will be increased significantly. This is especially challenging as the optical design is identical for all cameras, this is, optimized to meet the science objectives rather than to serve as a star-tracker. However, we have developed novel approaches to fit these goals. We will show in this contribution the status of the development of the Fine Guidance System of PLATO together with the latest performance estimates.