User Manual
Doc. Number: ESO-323064
Doc. Version: 2
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In Y-, J-, H- and K-bands the metrology converges reliably resulting in residual errors in
relative alignment of
0.1pix in main dispersion and
0.5pix in cross-dispersion. If the
metrology is not used the relative alignment is an order of magnitude larger. In P108 the
metrology should not be used for L- and M-band observations, its behaviour has not yet
been characterised in these bands (whilst it is known to be more challenging due to the
scarcity of suitable emission lines and the significant continuum from the pen-ray lamps).
An important note regarding main-dispersion stability following metrology:
During
commissioning it was observed that the drift in main-dispersion echellogramme alignment
was somewhat higher (~0.2pix over 30mins) following metrology alignment than it was
without metrology (0.05pix over 30mins, consistent with PAE measurements and
specifications). This effect is still being investigated and several mitigation strategies are
under consideration, but users should keep in mind that during P108 spectral resolution and
alignment of data obtained within 30mins of the application of metrology may be degraded
due to this effect.
3.2 The Warm Part
The Warm Part of CRIRES consists of different subsystems (see Figure 8
for an overview):
the AO Unit, the Calibration Unit which also includes a Fabry-Perot Etalon System and a
carriage stage with the new Polarimetry Unit and new sources for wavelength calibration
described in detail in Section 3.2.3.
Figure 8:
The upgraded CRIRES warm part assembly with etalon system, calibration slide,
AO system and de-rotator mechanism
MACAO
FP Etalon
System
Carriage Stage
Calibration Unit
Spectro-Polarimetry
Unit
