FOS Filter-Grating Wheel Repeatability
George Hartig
Space Telescope Science Institute

Instrument Science Report CAL/FOS049
October 1988


Abstract


The repeatability of the FOS Filter-Grating Wheel (FGW) was
re-measurecl during the March 1988 calibra.tion a.ctivities at
LMSC. Measurements were made ofthe repeatability in both X and Y at
the cainera rnirror positions on both red and blue eides, und in X for
7 dispersers on the blue side only. The FGW repeata.bility rema.ins
unsatisfactory, but ha.s appatently not deteriorated since the
previous measurements during the thermal/vacuum testing in 1986 und
axubient testing in 1985.