Hubble Space Telescope GHRS Instrument Science Report 072
GHRS Instrument Science Report 072
"A Review of the Utility of SPYBALs"
Lisa E. Sherbert and Stephen J. Hulbert
Many times users want to know how long they can observe without a
spectrum Y-balance (SPYBAL) in an effort to limit the motion of the
carrousel during an observation. This report discusses the rationale
for SPYBALS in terms of the drift of the spectrum across the
photocathode with time, taking into account the tilt of the spectrum
across the diode array. The results of our investigation reconfirm
that the default schedule of SPYBALs should be used to keep the
spectrum properly centered on the diode array.