Microarcsecond optical astrometry - an instrument and its astrophysical applications

Abstract

POINTS, an optical astrometric interferometer to be operated in space, would be a means of performing a wide variety of astrophysical studies, including a vastly improved deflection test of general relativity, a precise and direct calibration of the Cepheid distance scale, and the determination of stellar masses. The nominal 5μas uncertainty in the measurement of the angular separation of two stars about 90^deg^ apart in the sky and the estimated measurement rate of 60 star pairs per day would support a rich mixture of scientific projects during the nominal mission life of ten years. Useful results would be available after less than a year. The key to the instrument's success is the control of systematic error, which we address by instrumentation and postanalysis of the astrometric data.