The diversity of extrasolar planets (Gas Giants, Large Neptuns, Mini-Neptuns, Super-Earths, and Earth-like planets) is real and not an artefact of small-number statistics or a selection bias. It thus has to be caused by the formation and evolution of planets. What is still not known is how the statistics of the various types of planets changes over the whole mass range from F- to M-type stars. The Kepler survey of M dwarfs already indicates that there are dramatic differences. It is thus crucial to understand how the statistics of planets changes with stellar mass, which is the aim of this project.
Such a statistics only now becomes feasible with TESS (Transiting Exoplanet Survey Satellite). TESS is a big leap forward as it will cover an unbiased sample of F-, G-, K-, and M-stars. Previous experience with satellites, however, shows that the statistics can only be obtained when the false positives (FPs) are effectively removed by ground-based observations. The main source of FPs of space-based transit surveys are eclipsing binaries within the large point-spread-function of the space telescopes. TESS has a PSF of 40 arcsec. A special challenge for the ground-based observations is that the statistics of TESS for small and long-period planets will only be obtained within 12 degrees of the ecliptic poles. Because of the low stellar density there, the ground-based photometric observations require an unusually large field-of-view to provide a sufficient number of comparison stars of comparable brightness. The polar region is also important, because the small planets identified there are also the ones that can best be studied with the ESA/NASA mission JWST.
This calls for a dedicated survey for TESS follow-up observation close to the ecliptic north pole to exclude the FPs. Our Wide Field Transit Photometer (WFTP) will be build in collaboration between the Institute for Physics (Departement for Geophysics, Astrophysics, and Meteorology) of the University of Graz (Austria) and the Thüringer Landessternwarte Tautenburg (Germany).