AAS Meeting #194 - Chicago, Illinois, May/June 1999
Session 8. Space Instruments
Display, Monday, May 31, 1999, 9:20am-6:30pm, Southwest Exhibit Hall

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[8.12] The Full-sky Astrometric Mapping Explorer Concept Study

S.D. Horner, M.E. Germain (USNO), T.P. Greene (NASA Ames), F.H. Harris (USNO), M.S. Johnson (NRL), K.J. Johnston, D.G. Monet, M.A. Murison (USNO), J.D. Phillips, R.D. Reasenberg (SAO), P.K. Seidelmann (USNO), S.J. Talabac (Omitron), S.E. Urban (USNO), D. Van Buren (IPAC), R.H. Vassar (Lockheed Martin)

NASA has selected the Full-sky Astrometric Mapping Explorer (FAME) to be one of five MIDEX missions to be funded for a concept study. This concept study will be submitted to NASA on 18 June, with final selection, scheduled for September, of two of these missions for flight in 2003 or 2004.

FAME is designed to perform an all-sky, astrometric survey with unprecedented accuracy. It will create a rigid astrometric catalog of ~40,000,000 stars with visual band magnitudes 5 < V < 15. For bright stars, 5 < V < 9, FAME will determine positions and parallaxes accurate to < 50 microarcseconds, with proper motion errors < 50 microarcseconds/year. For fainter stars, 9 < V < 15, FAME will determine positions and parallaxes accurate to < 300 microarcseconds, with proper motion errors < 300 microarcseconds/year. FAME will also collect photometric data on these 40,000,000 stars in four Sloan DSS colors.

During the concept study, the team has worked to optimize the scientific return from FAME while minimizing cost and risk. The optical design was modified for improved accuracy of individual observations and improved mechanical design. The optical, mechanical, and thermal design of the instrument have been improved. Tests using CCDs in TDI mode are being conducted to confirm the accuracy obtainable from individual observations as well as determine the optimal clocking scheme for astrometric devices operated in TDI mode. The use of solar radiation pressure for spacecraft precession has undergone further feasibility study, as have the mechanisms for deploying the solar shield. Numerous other trade studies have been conducted, including orbit/communications, on board processing, and the use of neutral density filters for astrometry of bright stars versus other options. A detailed error budget has been formulated and the mission requirements have been defined.

We look forward to selection for launch and a successful FAME mission that will redefine the extragalactic distance scale and provide a large, rich database of information on stellar properties that will enable numerous science investigations into stellar structure and evolution, the dynamics of the Milky Way, and stellar companions including brown dwarfs and giant planets.

FAME is a joint development effort of the US Naval Observatory, the Smithsonian Astrophysical Observatory, the Infrared Processing and Analysis Center, Lockheed Martin Missiles and Space, the Naval Research Laboratory, and Omitron Incorporated.

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