Q: What photometric information is available from the guiding FGSs regarding the photometry of the Guide Stars?
A: Star Selector encoder readings and photomultiplier tube counts are available for Guide Stars at a 40 Hz rate for all astrometry observations.For non-astrometry observations taken after early 1995, 40 Hz Guide Star data is available; for observations made earlier, thtelemetryry format and frequency of the Guide Star data were generally determined by the science instrument, with frequencies ranging from 40 Hz to 0.667 Hz.