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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[8.05] FGS1r, HST's Interferometer That Can

E. Nelan, R. Makidon, L. Nagel (STScI)

The Hubble Space Telescope's Fine Guidance Sensor #1r (FGS1r) offers observing capabilities unmatched by either ground-based interferometers or space-based imaging systems, including those aboard HST. In high angular resolution mode, FGS1r can detect binary systems and measure the separation, position angle, and relative brightness of the components for stars separated by as little as 10 mas and system magnitudes as faint as mv=15. In astrometric mode, FGS1r can measure the relative positions of objects (including binary systems) distributed across its 69**2 amin FOV with a per observation precision of ~ 1mas over a dynamic range of 3 < mv < 17, thereby achieving sub-mas relative astrometry for multi-epoch observing programs. The FGS has also been used as 40hz photometer to temporally resolve a flare on an M dwarf and to observe the occultation of a star by the moon Triton. In this paper we present examples for each of these capabilities and compare FGS results to those of ground-based interferometers, astrometric observing facilities, and to HST's own WFPC2 imager. Astronomers can learn more about what the FGS can do by visiting our web site at the URL listed below.

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