QC PLOTS
	CURRENT	HISTORY
wavelength calibration		( soon)
intensity		( soon)
point spread function	(soon)	(soon)
QC1 database (advanced users): browse | plot
Click on CURRENT to see the current trending (Health Check).    Click on HISTORY to see the historical evolution of the trending.

Quality Control within the VLT data flow is mainly performed on calibration products. The main purpose is to monitor and asses the technical performance of the instrument and the atmospheric properties. E.g. a user defines a constraint of 1.0'' seeing. The executed OB is checked at the observatory immediately and the OB gets a QC grade within the QC0 process, meaning the constraint set is checked. The result of the QC0 process is a statement like: The seeing equals or is better than the constraint. When the science spectra are processed the average PSF of the spectrum can be derived from the science product. The QC1 parameter (in this case the QC1 parameter is dependent on the actual atmospheric seeing and instrumental parameters like the filter wavelength and the performance of the optical alignment like focus). The QC1 process although applied to science products still measures instrumental and atmospheric properties. It also measures properties of the sources (like source fluxes or intensities), but is does not measure how far the science products are suitable to perform the intended science goal of the underlying observing proposal.

QC1 parameters

parameter	QC1 database: table, name	procedure
wavelength calibration method	isaac_sci_spec, qc_wl_method	- the wavelength calibration method finally used (arc lines, sky lines or physical model). sky lines is the operational default for SW-arm telluric standard stars. For LW-arm telluric standard stars the operational default was arc lines; from P80 on sky lines are used.
central wavelength	isaac_sci_spec, qc_wlen	- the central wavelength in micron, derived from the dispersion solution
dispersion solution	isaac_sci_spec, qc_dispco1, qc_dispco2, qc_dispco3, qc_dispco4	- the wavelength calibration polynomial coefficients. dispco1 is the wavelength at pixel 1 , qc_wlen is the wavelength at pixel 512.
fit quality	isaac_sci_spec, qc_xcorr	- the wavelength calibration correlation coefficient. The wavelength calibration using sky lines is generally much better than for telluric standard stars due to the longer discrete integration times.
arc line results	isaac_sci_spec, arc_...	- the wavelength calibration results copied from the associated arc line calibration product
grating offset	isaac_sci_spec, qc_SA_offset	- grating offset between associated arc product and science spectrum ( = ( qc_wlen(telluric) minus qc_wlen(arc) ) in pixel
grating offset	isaac_sci_spec, qc_ST_offset	- system offset between skylines derived from the associated telluric standard star product and the sky lines derived from the science spectrum. Both QC.WLEN values are subtracted and converted in pixel. Values are of reliable if both wavelength calibrations are derived from the sky lines with qc_xcorr > 0.5.

Trending

QC1 parameters

QC1 parameters

QC report, showing the telluric standard star spectrum PSF fit results. The fit for science point source spectra is the same, in most cases the flux is smaller.

Trending

Parameters are collected since P80, they will be made available in the QC1 DB within 2008.