Microarcsecond astrometric observatory Theia: from dark matter to compact objects and nearby earths

Abstract

<i>Theia</i> is a logical successor to Gaia, as a focused, very high precision astrometry mission which addresses two key science objectives of the ESA Cosmic Vision program: the nature of dark matter and the search for habitable planets. <i>Theia</i> addresses a number of other science cases strongly synergistic with ongoing/planned missions, such as the nature of compact objects, motions of stars in young stellar clusters, follow-up of Gaia objects of interest. <i>Theia s "point and stare"</i> operational mode will enable us to answer some of the most profound questions that the results of the Gaias survey will ask. Extremely-high-precision astrometry at 1-&mu;as level can only be reached from space. The <i>Theia</i> spacecraft, which will carry a 0.8-m telescope, is foreseen to operate at L2 for 3,5 years. The preliminary <i>Theia</i> mission assessment allowed us to identify a safe and robust mission architecture that demonstrates the mission feasibility within the Soyuz ST launch envelope and a small M-class mission cost cap. We present here these features of the mission that has been submitted to the last ESA M4 call in January 2015.