The minimum COS exposure duration is 0.1 seconds (but FLASH=YES TIME-TAG
exposures impose a longer minimum; see Section 5.7.1
). The maximum is 6500 seconds. Between these extremes COS exposure times must be integer multiples of 0.1 seconds. If the observer specifies an exposure time that is not a multiple of 0.1 seconds, its value is rounded down
to the next lower integer multiple of 0.1 seconds, (or set to 0.1 seconds if a smaller value is specified). Exposure times larger than about 3000 seconds are normally appropriate only for visits with the Continuous Viewing Zone (which is a special requirement that must be requested and justified in the Phase I proposal) because the visibility period of a typical orbit is ~50 minutes. See the HST Primer
for information about HST
’s orbit and visibility periods.
(default) must be entered as the exposure time. The value appropriate for the optical configuration will be chosen from a table established at STScI for best performance. At present TARGET=WAVE
flash durations are identical to those given in Table 5.2