The various target-acquisition procedures are described in detail in Chapter 8
. The approximate total exposure plus associated overheads are given for each procedure below:
: Multiply the exposure time by the number of dwell points (SCAN-SIZE
^2) and add the overhead below to estimate the total ACQ/SEARCH time. These overheads include all OSM and aperture overheads.
Note that these overheads assume the standard (default) STEP-SIZE
of 1.767". Overheads are slightly shorter for smaller STEP-SIZE
: The associated overhead depends on the choice of MIRROR
and are 297s for MIRRORA
, and 335s for MIRRORB
; this include all OSM and most aperture overheads, and a 56s memory readout. If the aperture used is the BOA, add 5s in additional overhead. To estimate the total ACQ/IMAGE time add twice the exposure time to the overhead. The exposure time is doubled because, after HST slews to center the target, a confirmation image is obtained.
: The overhead is 84s for NUV, and 105s for FUV observations taken before Cycle 25. Add this overhead to the exposure time to estimate the total ACQ/PEAKXD time. For Cycle 25 FUV ACQ/PEAKXDs, use the timing outlined for ACQ/PEAKD. The default Cycle 25 ACQ/PEAKXD configuration uses NUM-POS=3
: Multiply the exposure time by the number of dwell points (NUM-POS
) and add the
specific overheads listed below. The numbers below assume the default STEP-SIZE
for each NUM-POS
as given in Table 8.3
. Add 37s for memory readout.