FOS Instrument Science Report # 126

"FOS Pre-COSTAR Target Pointing Analysis"
by Cynthia J. Taylor

Abstract excerpted from the report:

A log of Spacecraft Small Angle Maneuvers (SAM) during the Faint Object
Spectograph target acquisition sequence has been compliled from March
21, 1991 - December 3, 1993.  During this time there was no FOS Aperture
Location update to the Project Data Base (PDB).

Analysis of the log shows no obvious trends in: time, V2 direction, or
V3 direction.  The only trend seen is a systematic +V2 direction offset
for the dominant guide star FGS2. There is no trend seen for the dominant
guide star in either FGS 1 or FGS 3.

The lack of trends is due to the combination of several errors; target
coordinate error, guide star coordinate error, position of guide stars
within the Fine Guidance Sensors, FOS target acquisition method error, and 
other internal FOS errors (Filter Grating Wheel non-repeatability, GIMP,
etc.).





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