AAS 195th Meeting, January 2000
Session 46. Space Interferometry Mission
Display, Thursday, January 13, 2000, 9:20am-6:30pm, Grand Hall

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[46.05] Toward a Microarcsecond Extragalactic Frame Tie for SIM: HST Positions and Motions of Possible Grid Stars

A.A. Polak, E.P. Bozyan, P.D. Hemenway (University of Rhode Island), HST Astrometry Science Team

The upcoming Space Interferometry Mission (SIM) will obtain measurements at the microarcsecond level of accuracy. SIM requires an astrometric grid of approximately 4000 stars to define its reference frame necessary for global astrometry. In order for SIM's observed motions to be physically meaningful, the grid has to be referred to a nearly inertial (extragalactic) reference frame. A previous program, using the Fine Guidance Sensor (FGS) interferometer aboard Hubble Space Telescope (HST), contains possible grid stars in close proximity to extragalactic benchmarks. This project will obtain accurate positions and proper motions of these candidate grid stars from the FGS interferometric data. These stars also will provide SIM with a local reference frame necessary to determine and study internal motions of extragalactic benchmark objects during SIM's lifetime. The ultimate goal is to improve SIM's tie to the extragalactic reference frame.

The author(s) of this abstract have provided an email address for comments about the abstract: apol2215@postoffice.uri.edu

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