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FORS2 Quality Control
QC1 Parameters and Trending

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QUALITY CONTROL
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Trending & QC1
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QC links:
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detector bias
dark
gain & noise
gain & linearity
lamps imaging
spectroscopy
wavelength calibration long slit
MOS
PMOS  
MXU  
polarization optics
efficiency
zeropoints per frame and instrumental
extinction coefficients  per frame and nightly
science data sky brightness  
image quality

Find here detailed information about the FORS2 trending plots and select plots and data for download.
 

GENERAL INFORMATION


Some FORS2 calibration data are presently monitored to extract information about their quality and the instrument performance. The quality information is extracted into so-called QC parameters.

FORS2 calibration data are pipeline-processed to create calibration products. The quality of the products is measured by QC1 parameters. Most QC1 parameters are obtained by pipeline procedures; some are measured by post-pipeline recipes.

All measured QC1 parameters are stored in a database. Their evolution with time is evaluated by the trending process.

 

QC PROCESS


All FORS2 calibration products are quality-checked. While details of this process vary from case to case, some features are generally valid:

  • Raw frames and master frames are displayed and visually checked for anomalies.
  • When applicable, raw frames are checked for over-exposure (e.g. flats).
  • The distribution of pixel values is controlled in histograms. E.g., the distribution of pixel values in BIAS frames is checked to be consistent with statistical noise.
  • The product tables from format check and wavelength calibration frames are checked for number and distribution of fitted lines.

A calibration product is certified when experience shows that it measures the instrumental status in the proper way. This may mean that it complies with the expected result within certain limits. But it may also be true that it represents a valid outlier. E.g., after a realignment of a grating its X and Y shift against a reference frame will differ from the previous values, but this is a valid deviation.
 

INSTRUMENT PROPERTIES TRENDED


The following properties of FORS2 detector and instrument components are trended:

detector

zeropoints, efficiency, and image quality

wavelength calibrations


 
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