Results of the Guide-2 telescope testbed for the SIM Light Astrometric Observatory

The SIM Lite Astrometric Observatory is to perform narrow angle astrometry to search for Earth-like planets, and global astrometry for a broad astrophysics program, for example, mapping the distribution of dark matter in the Galaxy. The new SIM Lite consists of two Michelson interferometers and one star tracking telescope. The main six-meter baseline science interferometer observes a target star and a set of reference stars. The four-meter baseline interferometer (guide-1) monitors the attitude of the instrument in the direction of a target star. The Guide-2 telescope (G2T) tracks a bright star to monitor the attitude of the instrument in the other two orthogonal directions. A testbed has been built to demonstrate star-tracking capability of the G2T concept using a new interferometric angle metrology system. In the presence of simulated 0.2 arcsecond level of expected spacecraft attitude control system perturbations, the measured star-tracking capability of the G2T testbed system is less than 43 micro-arcsecond during single narrow angle observation.