The measurement principle of PLATO is to carry out high precision, long (months to years), uninterrupted photometric monitoring in the visible band of very large samples of bright (mV ≤ 11–13) stars. The resulting light curves will be used for the detection of planetary transits, from which the planetary radii will be determined, and for the asteroseismology analysis to derive accurate stellar parameters and ages. Since the PLATO targets are bright, the masses of the detected planets can be determined from radial velocity observations at ground-based observatories.
This animation shows a planet whose orbit is aligned in such a way that it crosses the disc of its parent star as seen from Earth: during these transits, the star appears less bright. By detecting these periodic decreases of brightness over time, it is possible to detect the presence of the planet orbiting the star.
ESA provides the spacecraft, the CCDs, the mission operations, and parts of the science operations. The PLATO Mission Consortium, funded by national Funding Agencies, provides the payload and contributions to the science operations.