Doc:
Issue
Date
Page
VLT-MAN-ESO-14650-4942
P96
24.06.2015
101 of 161
ESO, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
XSHOOTER_slt_acq_RRM=360+(Tel AG_EXPOSURE)*3+AG_EXPOSURE
XSHOOTER_ifu_acq_RRM=360+(Tel AG_EXPOSURE)*3+AG_EXPOSURE
if the AG_EXPOSURE time is setup at 1s:
XSHOOTER_slt/ifu_acq=360+(15+1)*3+1=409s
if the AG_EXPOSURE time is setup at 3mn or 180s:
XSHOOTER_slt/ifu_acq=360+(15+180)*3+180=1025s
If the AG exposure time is lower than 1s, the wiping time for doing the snapshot takes about
1s, therefore a minimum time of 1s is considered.
b) Setup overheads
In addition to these acquisition overheads, overheads regarding the instrument setup must
be added.
For the slit mode, the setup overhead is 30s, while for the IFU mode it lasts for 60s.
In the case of
Integration time of 1s
XSHOOTER_setup=409+30=439s
XSHOOTER_setup=409+60=469s
Integration time of 180s
XSHOOTER_setup=1025+30=1055s
XSHOOTER_setup=1025+60=1085s
In addition to these times, wiping time of the detector (6.1s) has to be taken into account and
the readout times.
c) Delay before start of exposures
In addition, there is a delay of 5 s before the start of the VIS exposure and a delay of 10 s
before the start of the NIR exposure.
d) Readout overheads
Because the UVB and VIS arms share the same FIERA controller, if the exposure of CCD1
ends while the controller is reading CCD2, the readout of CCD1 will only take place once the
readout of CCD2 is finished.
This must be compared to the execution of the NIR arm and the slowest of NIR vs
UVB + VIS arms gives the final execution time.
In case the readout of the UVB, VIS detectors is performed consecutively, one has to sum
their readouts (and if the NIR arm ex readout is finished before).
If the VIS exposure is longer than the UVB ex UVB readout and the NIR ex
the NIR readout, then the execution time will correspond to the VIS exposure + the VIS
readout time.