Precision astrometry mission for exoplanet detection around binary stars

We propose an innovative low-cost mission capable of detecting potentially habitable planets around a sample of solar-type stars near the sun. Our mission will deliver relative measurements of stellar position and motion at sub-micro acrsecond precision. These data, in turn, will reveal the presence of orbiting exoplanets. For the case of our primary targets Alpha Centauri A & B, objects below one Earth mass will be accessible when the end-of-mission astrometric precision requirement of 0.4 micro-arcsecond is achieved. The technique will directly reveal not only the presence of the planet but deliver fundamental data such as masses and 3-D orbital parameters including eccentricity and inclination. This paper describes the optical and mechanical architecture of the mission and first-order instrument design. We also explain the instrument stability requirements imposed by the diffractive pupil post-processing calibration limitations. Our design baseline is a stable two-mirror telescope that images the field directly on CCD camera minimizing the number of reflections and optical components.