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VIRCAM Quality Control:
Parameters and Trending

CAL | HC | refs | QC
Trending & QC1
trending & QC1
QC links:

VIRCAM 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.

The following properties of VIRCAM detectors and instrument components are trended:



overall properties



All QC1 parameters extracted from calibration products (and in some cases from raw frames) are archived in the central public QC1 database.The database is organized as follows: There is for each VLT/I instrument a set of tables. In most cases each table contains the QC1 parameters related to a product type or a raw type, e.g. DARK, or DOME. Each of the tables contain three sections: a general section with time keys like MJD-OBS and file name keys, a QC section containing the QC1 value for each product type, and the instrument section with the parameters on which the QC1 values depend. E.g. a QC1 value called 'photometric zeropoint' depends on the ins parameter 'filter'. For each table there are two interfaces. A plotting interface and an interface to download the QC1 parameters.VIRCAM raw frames and pipeline product frames come as single fits frames with 16 extensions; each extension contains the read out of one detector. All processing is done per extension. Therefore the QC1 parameters generated by the pipeline are obtained per extension and are written into the the 16 individual extension headers. As a consequence each QC1 parameter describes only one of the 16 detectors and the detector ID is handled in the same manner as an instrumental setup. All tables of the VIRCAM QC1 database provide several variants of the detector ID for reasons of flexible selection:

  • det_chip_id (from HIERARCH ESO DET CHIP ID), e.g. "ESO-Virgo52" [varchar]
  • det_chip_no (from HIERARCH ESO DET CHIP NO), e.g. 13 [int]
  • extname (from EXTNAME), e.g. DET1.CHIP12 [varchar]

The VIRCAM QC1 database contains the QC1 parameter for all extensions (EXTNAME = DET1.CHIP1 ... DET1.CHIP16) and two aggregates (see e.g. the QC1 databases of the multi-detector instruments CRIRES, VIMOS and HAWK-I):

  • the mean value of the QC1 parameter, averaged over all 16 detectors (EXTNAME = AVG)
  • the standard deviation obtained from the same sample (EXTNAME = RMS)

The QC1 database project started with the begin of VIRCAM commissioning in 2008-10-01. Further tables may have to be generated for QC1 parameters.


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

  • Newly derived QC1 parameters are displayed and outliers are checked for possible assignable cause.The quality of raw frames and master calibrations is checked via a scoring mechanism. In case the score is not reached, a detailed analysis is triggered which can include visual inspection of the raw frames and the pipeline products.
  • 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.