PLATO – PLAnetary Transits and Oscillations of stars – is a medium-class mission within the European Space Agency’s (ESA) Cosmic Vision program, with a planned launch by the end of 2026. Its primary goal is the detection and characterization of terrestrial exoplanets within the habitable zones of solar-type stars by analyzing their transit signatures across a large sample of bright stars. Additionally, the mission measures the seismic oscillations of the host stars to better understand the properties of these exoplanetary systems.

The PLATO payload consists of an instrument equipped with 26 cameras for stellar observation: 24 standard cameras grouped into four subsets of six cameras each, and two fast cameras. Beyond providing scientific data for very bright stars, the fast cameras also serve as a redundant Fine Guidance System (FGS) and are integrated into the Attitude and Orbit Control System (AOCS). This ensures exceptional pointing precision, which is essential for achieving high photometric accuracy.

A critical requirement for using a camera in guidance tasks is an accurate geometric calibration of the instrument. For PLATO, a generalized geometric camera model, combining a pinhole camera model with a distortion model, has been adapted to accommodate the unique camera setup. This model enables the transformation between sky coordinates and image coordinates and vice versa. The parameters of the camera model are estimated using both an on-ground calibration pattern and stellar observations for in-flight calibration.