The PLATO mission will monitor the brightness variations of more than 200,000 stars to look for planets which transit their host stars. TESS will also utilise the transit technique to focus on targeting bright host stars, to look for Earth-sized planets. It is thus not surprising when people end up thinking: why launch two spaced based exoplanet spacecraft to look for Earth-sized planets?
The Transiting Exoplanet Survey Satellite (TESS) launched in April 2018 and has already started science operations. The two-year all-sky transit survey, like PLATO, will monitor more than 200,000 stars and be able to detect Earth-sized planets currently out of reach of ground based observatories.
With TESS being an all-sky survey, it won’t focus on any particular patch of sky for longer periods of time, but will instead move around. The exceptions being the more polar areas which have overlapping regions as shown in the figure below. The mission was designed this way: find the exoplanets orbiting the brightest stars all over the sky.
Owing to this mission goal, TESS will not be able to detect Earth-sized planets in ...