Interferometric survey of stellar parameters
Fundamental stellar parameters are the primary data required for an in-depth understanding of stars, their interiors, and their environments. With the progress of stellar physics and the prospects of ground facilities or space missions, it is critical to improve the accuracy, and quantity of such data. The development of exoplanet and asteroseismology domains is demanding direct data to eliminate any bias in the parameters. And finally, the differences between methods for determining the Hubble constant is motivating new and precise direct determination of distances on the primary candles of the cosmic scales. Many methods like asteroseismology, photometric transits of exoplanets, radial velocities, or Surface Brightness Colour (SBC) relations are linked to the stellar radius. Usually estimated through models, its determination by coupling an optical interferometric measurement of the angular diameter and, for example, a Gaia parallax, is the best way to avoid any model dependence. Furthermore, characterizing any activity (limb darkening, convection, rotation, spots, or binarity) is also mandatory, both for bias removal and for the required progress on stellar physics. 
Through an ambitious and homogenous survey of the angular diameters of a thousand stars as faint as magnitude 8 in the visible and as small as 0.2 milliseconds of arc, my project is built to address key questions about the relation between planets and stars and to offer to the broader community a unique and primary source of direct information on a representative and large sample of stars all over the HR diagram. A few hundred of direct measurements of limb darkening will be accessible, and, for about 100 stars, activity characterization with a more detailed surface imaging will be possible. These data will also permit the development of new unbiased SBC relations to serve the faint targets of space missions like PLATO or ARIEL in the future and the distance scale within the Araucaria project.