Space Interferometry Mission (SIM)
Benedict and Barbara McArthur are co-Investigators on a SIM Key Project, MASSIF. Todd Henry at Georgia State University is the P.I. We intend to establish a precise mass-luminosity relation over the entire range of stellar masses. This will require astrometry with 4 micro arcsecond precision. This diagram compares the end-of-mission astrometric precision of HIPPARCOS, HST-FGS, FAME, and SIM.