Quality Control and trending

Find here detailed information about the UVES QC1 parameters and select plots and ASCII files from the QC1 database.

UVES 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.

• all calibration products measured in UVES standard modes
• occasionally non-standard master_BIASes (1x2 and 2x3 binnings) are included

All UVES 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.
 

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

• BIAS level and read noise, see also CCD Tests
• DARK current
• Parasitic Light

• gratings
• stability of spectral format
• resolving power
• precision of dispersion solution
• crossdisperser alignment

• gratings
• stability of spectral format
• resolving power
• precision of dispersion solution
• crossdisperser alignment
• lamps
• Lamp stability