KMOS: Wavelength calibration
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HC PLOTS |
spectral resolution (Ar lines) |
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spectral resolution (Ne lines) |
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wavelength solution |
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Ar lamp |
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Ne lamp |
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QC1 database (advanced users):
browse |
plot
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Arc-lamp calibrations are measured during daytime for the five wavelength
bands IZ, YJ, H, HK, and K and for six different rotator angles. A
standard calibration sequence uses rotator angles of -60 (i.e. 300), 0, 60, 120,
180, and 240 degrees. Two lamps are used simultaneously: one Argon and one
Neon lamp.
Each IFU comprises 14 slices. Eight IFUs form a sub group which is mapped on a
single slit. The light is then dispersed through one of the three
spectrographs and recorded on one detector array (out of three). There are
three independent optical channels, each having eight IFUs.
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Arc-lamp exposure. Example frame in the H band. Each IFU slitlet corresponds to one vertical stripe with a width of 14 pixels on the detector. 14 slitlets form one IFU.
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Spectral resolution
QC1_parameters
KMOS arc-lamp frames are usually taken at six different rotator angles. These
fill the QC parameters, for example ar_fwhm_mean__1, ar_fwhm_mean_2, ..., ar_fwhm_mean_6, etc. The actual
angles can be found in the parameters rot_angle_1, rot_angle_2, ...,
rot_angle_6. The parameter ar_fwhm_mean_0 is only filled if a measurement at 0
degree rotator angle is present which is typically the case for daytime
calibrations.
FITS key |
QC1 database: table, name |
definition |
class* |
HC_plot** |
more docu |
QC.ARC.AR.FWHM.MEAN | kmos_wave..ar_fwhm_mean_0 | mean FWHM of Ar lines [km/s], 0 degree rotator angle | HC | | [docuSys coming] |
QC.ARC.NE.FWHM.MEAN | kmos_wave..ne_fwhm_mean_0 | mean FWHM of Ne lines [km/s], 0 degree rotator angle | HC | | [docuSys coming] |
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter
**There might be more than one. |
Trending
The spectral resolution is monitored for Ar and Ne lines separately. Trending
is performed for all five spectral bands. The QC parameters at 0 degree
rotator angle (ar_fwhm_mean_0, ne_fwhm_mean_0) are plotted versus time and
scored. The dependency from rotator angle is shown in separate plots (not
scored).
Scoring&thresholds Spectral resolution
The QC parameters at 0 degree rotator angle (ar_fwhm_mean_0, ne_fwhm_mean_0) are scored.
Scoring thresholds have been set empirically to +/- 3 sigma
around the median (determined from data taken between 15 August and 30 November 2018).
History
Small changes in spectral resolutions could be observed sometimes after interventions.
Algorithm Spectral resolution
Average FWHM of arc lines, calculated separately for Ar and Ne lines and converted to km/sec.
Wavelength solution
QC1_parameters
FITS key |
QC1 database: table, name |
definition |
class* |
HC_plot** |
more docu |
QC.ARC.AR.POS.MEAN | kmos_wave..ar_pos_mean_0 | mean position offset of Ar lines [km/s], 0 degree rotator angle | HC | | [docuSys coming] |
QC.ARC.NE.POS.MEAN | kmos_wave..ne_pos_mean_0 | mean position offset of Ne lines [km/s], 0 degree rotator angle | HC | | [docuSys coming] |
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter
**There might be more than one. |
Trending
The mean deviation of the line positions is monitored for Ar and Ne.
Trending is performed for all five spectral bands. The QC
parameters at 0 degree rotator angle (ar_pos_mean_0, ne_pos_mean_0) are
plotted versus time. The dependency from rotator angle is shown in
separate plots.
Scoring&thresholds Wavelength solution
Scoring is not implemented.
History
The wavelength solution was stable over time.
Algorithm Wavelength solution
As a measure of the quality of the wavelength calibration, the deviation (in
km/s) of the actual line positions from the fitted wavelength solution is
calculated.
Arc-lamp performance
QC1_parameters
FITS key |
QC1 database: table, name |
definition |
class* |
HC_plot** |
more docu |
QC.ARC.AR.EFF | kmos_wave..ar_eff_0 | Ar lamp brightness [e-/s], 0 degree rotator angle | CAL | | [docuSys coming] |
QC.ARC.NE.EFF | kmos_wave..ne_eff_0 | Ne lamp brightness [e-/s], 0 degree rotator angle | CAL | | [docuSys coming] |
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter
**There might be more than one. |
Trending
The lamp flux is monitored in the YJ band separately for Ar and Ne and for all
three optical channels. The parameters ar_eff_0 and ne_eff_0, respectively,
are trended versus time. Since the efficiency does not strongly depend on
rotator angle, only ar_eff_0 and ne_eff_0 are scored. The dependency against
rotator angle is shown in separate plots.
Scoring&thresholds Arc-lamp performance
The QC parameters at 0 degree rotator angle (ar_eff_0, ne_eff_0) are scored.
Thresholds have been set empirically. A lamp flux that is approaching the
upper limit is typically an indication that the lamp is at the end of its life
time.
History
The Neon lamp had to be exchanged a few times. It typically lasts up to 18
months.
Algorithm Arc-lamp performance
Pipeline calculated average flux of arc lines, converted to e-/sec.
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