The Micro-arcsecond Astrometry Small Satellite: MASS

In the search for exoplanets, one of the most sought-after goals from the outset has been to survey nearby systems for Earth-mass planets in their habitable zones. Because of their relatively low mass and size, and their separation from their host stars, these most prized targets have been elusive so far. High precision astrometry is an indirect method that is complementary in its reach to those of the Doppler and photometric transit methods. The Micro-arcsecond Astrometry Small Satellite (MASS), is a concept astrometric mission utilizing a small space telescope and ultra-precise focal plane and field distortion calibration. In one version, recently proposed as a NASA mission of opportunity, MASS's performance was evaluated with a 35 cm primary mirror and a 150 Mpix scientific CMOS sensor, and was estimated to achieve a single-look accuracy of 6 µas. Even with this modest telescope, MASS would have the sensitivity needed to find a 1 Earth-mass planet at 1 AU orbit (scaled to solar luminosity) around the ~5 nearest FGK stars and 2 Earth-mass planets around an additional ~15 nearest stars. MASS would be able not only to measure masses of these exo-Earths but also characterize their orbits for follow- on direct detection missions such as HabEx or LUVOIR. In this presentation we describe the proposed mission, the precision astrometric technique, and the results from testbed demonstration of the technique.