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[4.10] The Suitability of Guide Star Catalog 2 (GSC-2) as a Source for JWST Guide Stars

J. Stys, G. Kriss (Space Telescope Science Institute)

Guide Star Catalog 2 (GSC-2) is the deepest and most complete all-sky source of guide stars for space astronomy missions. However, this catalog is based on ground-based photographic plate material. The Fine Guidance Sensors (FGS) on the James Webb Space Telescope will be near-infrared imaging cameras. The majority of stars visible in these cameras will be very red late-type stars populating the faintest end of GSC-2. We study these likely guide stars in detail by comparing a 2-square-degree region of the sky as catalogued by GSC-2, the Sloan Digital Sky Survey (SDSS), and the Two-Micron All-Sky Survey (2MASS) Point Source Catalog. We find that GSC-2 catalog entries can only be reliably converted to infrared magnitudes to a limit of J_ab~17.4, and that the contamination rate at these magnitudes by unsuitable objects (galaxies, double stars, non-existent objects) is <10%. For a nominal FGS field of view of 8.4 square arc minutes, GSC-2 provides enough catalogued guide stars at infrared J magnitudes 18-19 at galactic latitudes |b| > 30^o to meet the JWST Level 2 requirement of a 95% probability of a successful guide star acquisition anywhere in the sky.

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Bulletin of the American Astronomical Society, 35 #3
© 2003. The American Astronomical Soceity.