What observation modes does GALEX have?
All science data collection uses a spiral dither, to prevent bright-star-induced fatigue of localized regions on the detectors and to improve image flat-fielding. In “single-visit” or “stare/dither” mode, only one field center is observed for an entire eclipse. In “sub-visit observations”, or “AIS (All-sky Imaging Survey) mode”, several (typically 10-12) contiguous field centers are observed during one orbital night. Grism observations are always done in “single visit” mode; multiple observations are made at different grism orientations and then combined. GI observations may only use these standard GALEX observing modes.
