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Session 16 - Astrometry.
Display session, Wednesday, January 07
Exhibit Hall,

[16.05] Astrometry with HST\'s FGS#3

E. Nelan, O. Lupie, L. Nagel, R. Makidon (STScI), G. F. Benedict, B. McArthur (U. Texas at Austin), O. Franz, L. Wasserman (Lowell Obs), L. Abramowicz-Reed (Hughes Danbury Optical Systems)

The Hubble Space Telescope's Fine Guidance Sensors (FGS) are optical interferometers that offer a unique astronomical capability. HST's light gathering power and the FGS's dynamic range combine to provide astronomers with an unparallelled science instrument for many important investigations. Among the FGS's many applications are the resolution of multiple star systems, detections of planetary companions, delineation of objects in crowded fields, measurements of stellar angular diameters, parallax and proper motion determinations, and photometric measurements. The FGS can measure point source angular separations to an accuracy of 1-2 milli-seconds of arc (mas) over a brightness range of 3 to 17 magnitudes, as well as resolve the components of a binary system when their angular separation is as small as 15 milli-arcseconds. It is also a stable 40hz photometer. In many applications, the FGS continues to exceed ground and space based efforts in both sensitivity and resolution. We will discuss the impact of HST's spherical aberration and the temporal variability of the HST/FGS system, and demonstrate how they were reduced, by a combination of observing strategies and calibations, to restore the performance of the FGS#3 to exceed its pre-launch expectations as a scientific interferometer.

Program listing for Wednesday