CRIRES User Manual
Doc. Number: ESO-254264
Doc. Version: P109.4
Issued on:
2021-12-01
Page:
56 of 99
Document Classification: ESO Internal Use [Confidential for Non-ESO Staff]
Select Plots
tab:
•
By default, the ETC displays the S/N ratio per spectral pixel, however the user can
request different plots related to the sky and/or target signal, and to the throughput
efficiencies.
•
It is always useful to ask the ETC
to show the S/N ratio as a function of wavelength
due to the presence of numerous telluric features: a small difference in the
requested wavelength can lead to very different S/N ratio for a given total integration
time or, alternatively, very different integration time for a requested S/N ratio.
•
From the ETC page users can access to a python script that allow to download the
output of the requested plots in ascii file. These scripts can be found under the
“Tools” tab.
•
All wavelengths displayed in the ETC are in vacuum
.
5.6 Instrument overheads
In Phase 1 users are requested to provide the total execution time, which is given by the
total exposure time on target (i.e., open-shutter time) plus the overheads. The estimated
overheads related to both telescope and instrument are listed in the following table.
Table 9: Telescope and Observation overheads. (*) If the metrology is enabled in the
acquisition template, but not the science template(s), then no overheads associated to the
metrology apply. (**) If done during acquisition or in parallel with a change of the wavelength
setting, the corresponding overhead listed here does not apply. (***) The derotator cannot
move beyond 359.9 degrees. Thus, changing the derotator position angle from, for
example, 350 to 10 degrees will take 74 seconds, as it will rotate by 340 degrees.
Action
Times (s)
Telescope
Preset
360
CRIRES
Acquisition with AO
240
CRIRES
Acquisition without AO
150
CRIRES
Read-out for one exposure
2.4 + 1.43 x (NDIT-1)
CRIRES
Nodding cycle
28
CRIRES
Change of wavelength setting
80
CRIRES
Metrology in Y, J and H*
110
CRIRES
Metrology in K*
160
CRIRES
Metrology in L*
200
CRIRES
Attached wavelength calibration
180
CRIRES
Attached lamp flat
90
CRIRES
Change of derotator position angle**
2 + 76 x abs(PA1-PA2) / 360***
CRIRES
Change of polarimeter setting**
23
CRIRES
Generic Offset
14