Next: HEASARC Data Levels
- A snapshot is the time spent contiguously observing
a target. This time is shorter than a single orbit due to
interruptions from other targets, Earth occultation, and other
- This term is used to organize data in the Swift Data Archive. An observation is a collection of
snapshots on a single target where the roll angle remains more or
less constant across the separate snapshots.
- This term is used only to organize the UVOT data
into FITS files by mode (image or event) and filter. An exposure
is defined as the time UVOT spends in the same general state for
all parameters: mode, window size and filter.