[Previous] | [Session 63] | [Next]
G. F. Benedict, B. E. McArthur (McDonald Observatory), E. P. Nelan (STScI), W. H. Jefferys (Astronomy, UTexas)
We report on our progress towards an astrometric calibration of Fine Guidance Sensor 1r, installed during an HST refurbishment mission a few years ago. The calibration of this space-based interferometer will complete the commissioning of FGS1r as a sub-milliarcsecond astrometric science instrument for Cycle 10 and all future HST cycles, and permit the final reduction and analysis of ~100 orbits of FGS1r data acquired by a variety of GO programs during HST Cycles 8 and 9.
These calibration data were secured in December 2000. We map the optical field angle distortions of FGS1r to facilitate the goal of millisecond of arc precision astrometry for FGS1r's fringe tracking (Position) mode. Our results will populate the FGS1r calibration database and will be available to all FGS GOs through the use of STScI's calibration pipeline.
A second result will be an improved M35 calibration field, one that takes into account proper motions in the catalog. This will allow for more accurate monitoring of the FGS1r plate scale and distortions during future HST cycles.