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Quality Control and
Data Processing


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QUALITY CONTROL
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XSHOOTER QC
Trending & QC1
   wavecal
Pipeline
QC links:
XSHOOTER: Wavelength solution and resolution
Wavelength calibration | Resolving power

 
HC PLOTS
UVB number of lines, resolution, 9pin vs. slitpos SLIT
VIS
NIR
UVB number of lines, resolution, 9pin vs. slitpos IFU
VIS
NIR
QC1 database (advanced users): browse | plot

The arc lamp exposures with the slit are not used for processing but only for quality control monitoring. The pipeline identifies the lines using the same catalog as for the distortion correction. Then the resolution and the difference between the position of a given line in the 9-pinhole observations and that in the slit observations is determined. The physical model configuration parameters are not updated.


Wavelength calibration
Wavelength calibration | Resolving power

QC1_parameters

FITS key QC1 database: table, name definition class* HC_plot** more docu
QC.WAVECAL.FOUNDLINE xshooter_wavecal..nline_found number of arc lines foundCAL [docuSys coming]
QC.WAVECAL.DIFFY.MED xshooter_wavecal..model_diffy_med median difference between model predictions and found lines CAL [docuSys coming]
QC.WAVECAL.DIFFYSTD xshooter_wavecal..model_diffy_rms rms of difference between model predictions and found lines CAL [docuSys coming]
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter
**There might be more than one.

Trending

The number of arc lines found in the through slit arc lamp exposure is monitored in the upper left box of these plots UVB, VIS and NIR.

The differences between the 9-pinhole solution and the slit solution is monitored in the same plots, but in the lower left and lower right boxes.

The number of arc lines found in the through IFU arc lamp exposure is monitored in the upper left box of these plots UVB, VIS and NIR.

The differences between the 9-pinhole solution and the IFU solution is monitored in the same plots, but in the lower left and lower right boxes.

Scoring&thresholds Wavelength calibration

The number of found lines and the median difference is scored. The threshold for the number of lines is 10% of the median value. The thresholds for the difference values is based on statistical grounds.

History

Date event
2010-01-26 new NIR lamp provides brighter lines
2010-06-01 VIS lamp provides about 30% more flux; more lines found
2010-06-01 UVB lamp provides about 20% more flux; more lines found
2010-10-07 pipeline version 1.1.6 has changed the values of several QC parameters, esp. line intensity, number of lines found and differences with respect to model predictions
2010-11-08...2010-11-20 pipeline problems with number of accepted lines in NIR
2010-12-17 Ne lamp in NIR arm dies
2011-02-15 Ne lamp in NIR arm replaced
2011-02-20 Xe lamp in NIR arm replaced; Ne lamp in NIR arm aligned correctly
2011-07-07 new slit mask in NIR: QC parameters may change slightly due to manufacturing tolerances; 0.4" pinhole and 1.5"x11" slit are replaced by 0.6"x11" and 0.9"x11" slits with K-band blocking (resulting in fewer orders and lines for these slits (0.6x11JH, 0.9x11JH) compared to their unblocked equivalents.
since_2011 Flat field lamp replacements are marked in the flat spectrum health check plots.
2017-10 The deviations of the 9-pinhole positions from the physical model fit, as reported in the QC report, have been marked by different colors by order.

Algorithm Wavelength calibration

Chebyshev polynomials are fit to the arc line echelle spectrum


Resolving power
Wavelength calibration | Resolving power

QC1_parameters

FITS key QC1 database: table, name definition class* HC_plot** more docu
QC.RESOLMED xshooter_wavecal..resol_med median resolution CAL [docuSys coming]
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter
**There might be more than one.

Trending

The median spectral resolution derived from wavelength calibrated arc lamp SLIT spectra is monitored in the upper right box of these plots UVB, VIS and NIR.

The number of arc lines found in the through IFU arc lamp exposure is monitored in the upper right box of these plots UVB, VIS and NIR.

Scoring&thresholds Resolving power

The resolving power is an instrument key performance indicator and is scored. For SLIT, the current thresholds are 5% of the median, for IFU, with a larger intrinsic scatter, the thresholds are 10% of the median.

History

Date event
2011-06-04 During July 4-8, 2011, a new slit mask was installed in the NIR arm. The 0.4" pinhole and the 1.5"x11" slit were replaced by an 0.9"x11" and an 0.6"x11" slit with K-band blocking (0.9x11JH, 0.6x11JH). The change of slit mask resulted also in small changes of resolution for the other slits since the new and old slits are not exactly identical (manufacturing tolerances).
2017-12 We modified the hitherto used default command line parameter of the xsh_wavecal recipe from --followarclines-search-window-half-size=6 to --followarclines-search-window-half-size=13, which allows for a larger window pixel size when searching for arc lines. For 1x2 binning arc frames, the parameter covers a double as large wavelength range than for 1x1 binning, (since binning two detector pixel into one frame pixel covers the same wavelength range). The effect is negligible for IFU frames, 1x2 binning setups and 1x1 narrow slit arc frames, and strongest for wide slit 1x1 binning slit arc frames.
2017-12 The spectral resolution (= resolving power) reported by the xshooter pipeline was biased by about 19% (1x1 binning UVB 1.0x11) and 15% (1x1 binning VIS 0.9x11) arc frame calibrations from begin of operations on. The pipeline arc frame recipe underestimated the spectral resolution. The pipeline results for 1x2 binning data were closer to measurements retrieved directly from the product frames. The trending plot for 1x1 binning arc frames did not show the absolute resolving power, but still monitored the long-term trend.

Algorithm Resolving power

Chebyshev polynomials are fit to the through slit arc line echelle spectrum.


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