CRIRES User Manual
Doc. Number: ESO-254264
Doc. Version: P109.4
Issued on:
2021-12-01
Page:
71 of 99
Document Classification: ESO Internal Use [Confidential for Non-ESO Staff]
The total integration time of one exposure in an OBJECT location is
DET1.NDIT.OBJECT
x
DET1.DIT
. Similarly, the total integration time of one exposure in SKY location is
DET1.NDIT.SKY
x
DET1.DIT
. Note that
SEQ.NEXPO
exposures can be obtained at each location.
In the case of NGS observations, OBJECT and SKY correspond to MACAO CLOSE and
OPEN loop, respectively. The total exposure time for one generic offset template is:
DET1.NDIT.OBJECT
x
DET1.DIT
x
SEQ.NEXPO
x
N
Obj
+ DET1.NDIT.SKY
x
DET1.DIT
x
SEQ.NEXPO
x
N
Sky
where N
Obj
is the number of object positions and N
Sky
is the number of sky positions.
6.4.4 Spectro-astrometry details
The CRIRES_spec_obs_SpectroAstrometry template allows to apply the spectro-
astrometry technique without having to re-acquire the target for each position angle. Note
that the derotator mode (TSF:
INS.DROT.MODE
) needs to be set to SKY in the acquisition
template, and that the TARGET must be the SVGS and the AO NGS. For this reason, the
CRIRES_spec_obs_SpectroAstrometry template cannot be used with differential tracking.
·
List of position angles
(TSF:
INS.DROT.POSANG.LIST
) is the list of position angles at which
the nodding sequence is repeated. Note that these values of the position angles are in the
range between 0 and 360, where 0 corresponds to North and 90 to East. When calculating
the overheads, keep in mind that the derotator can only move between 0 and 359.9 degrees.
·
Reset jitter for each DROT posang
(TSF:
SEQ.JITTER.RESET
). Only relevant if
SEQ.JITTER.WIDTH
(Jitter width) is not zero. If this parameter is set to
yes
(i.e.,
SEQ.JITTER.RESET
=T), then the list of jitter positions calculated by the observation software
is repeated identically, in detector coordinates, for each value of the slit position angle
In the spectro-astrometry case, the total exposure time for one observing template with
nodding is:
2 x
SEQ.NABCYCLES
x
DET1.NDIT
x
DET1.DIT
x
SEQ.NEXPO
x N
posang
where N
posang
is the number of position angles defined in
INS.DROT.POSANG.LIST.
For the
stare-mode (
SEQ.NABCYCLES=0
), the total exposure time is:
DET1.NDIT
x
DET1.DIT
x
SEQ.NEXPO
x N
posang.
6.4.5 Spectro-polarimetry details
Remember that for observations with polarimetry, the CRIRES_pol_acq_NGS acquisition
template must be used.
