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Astrometric Reference Frame Science

Astrometric Reference Frame Science Kenneth J. Johnston (UsNO), Ann E. Wehrle (space science Institute), Valeri Makarov (NExscI), David W. Murphy (JPL), Stephen C. Unwin (JPL), Norbert Zacharias (UsNO), Alan L. Fey (UsNO), Roopesh Ojha (UsNO), and David A. Boboltz (UsNO) The establishment of an inertial reference frame based on grid stars anchored with extragalactic sources will allow for the first time the direct detection of the motion of the Solar System within the Milky Way as well as the Local Group toward the Virgo cluster at the μas/year level. All of this will be accomplished by observing stellar motions with respect to distant “fixed” quasars, which provide an inertial frame against which absolute proper motions can be measured. At the same time, this inertial frame enables possible detection of the apparent motion of the center of light of some “peculiar” quasar sources. By establishing an accurate link between the optical SIM Lite frame and the radio International Celestial Reference Frame (ICRF), high-resolution imaging data at these different wavelengths can be accurately lined up for absolute positional correlation. This enables a better understanding of the mechanisms giving rise to their spectral energy emission.