CRIRES User Manual
Doc. Number: ESO-254264
Doc. Version: P109.4
Issued on:
2021-12-01
Page:
26 of 99
Document Classification: ESO Internal Use [Confidential for Non-ESO Staff]
The major advantages are comb-like, equidistant reference lines over the design range with
high homogeneity, equally strong spectral features, broadband coverage with no gaps and
a high line density. The FPI subsystem comprises a sealed vacuum vessel, standard ESO
vacuum pump and a halogen light source. The vessel is pressure tight. Sub-atmospheric
pressure is achieved by daily pumping (duration ~30 min) to ≤10
-3
mbar;; this pumping
process is independent of the main spectrograph cryo-vacuum subsystem. An interlock
valve closes the FPI chamber in case of pump failure. All three components are secured on
a bench in the base of the warm structure (Figure 19). The FPI feeds a fibre which delivers
the FPI spectrum to the integrating sphere. The calibration system is described in detail in
articles by Seemann et al. (2014, 2016 and 2018).
3.2.3.3 Summary of the calibration sources
Table 1: Summary of the different calibration sources available for CRIRES
Type
Principal
use
Location
Notes
(Atmospheric
lines)
Wavelength
calibration
Sky
L & M band where the lamps have few lines
and continuum
Halogen lamp
Flat
Fields
(YJHKLM)
Integrating Sphere
Extended spectrum/black body, temperature:
3000-3100K. Can be attenuated with the
baffle.
IR black body
source
Flat
Fields
(LM)
Integrating Sphere
Extended spectrum/black body, temperature:
1100-1150K. Can be attenuated with the
baffle. Not a part of routine flat field calibration.
Krypton & Ne
pen-ray
lamps
Metrology
Integrating Sphere
Sparse spectral features, which however
provide an easily reproducible uniform
illumination of the entrance slit for metrology.
Can be attenuated with the baffle
He-Ne Laser
Alignment,
health checks
on resolution
Feeds Integrating
Sphere
Dual wavelength 1.1526μm and 3.3922μm.
Coupled to an IR fibre that will transmit both
lines that feeds the IS.
U/Ne HCL
Wavelength
calibration
On carriage
Dense spectral features up to K-band.
Illuminates the entrance slit uniformly. Serves
as absolute wavelength reference.
U/Ar HCL
Alignment
tool
Feeds
seven
“metrology fibres”
Originally intended for use with metrology but
no longer part of routine operations. Still a vital
alignment tool that bypasses the cross-
dispersion.
New
Gas-
Cells
Wavelength
calibration
On carriage
Customised mixture of Ammonia, Acetylene
Methane-13. Uniform set of absorption lines in
the range of CO band.
