QC PLOTS
	CURRENT	HISTORY
source parameters
environmental parameters
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 images are processed the average image quality 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.

There follows for each dark product type a QC1 plot. The first two are of the Hawaii array, the latter three are of the Aladdin array. The Figure caption is equal for all four plots.

• Example SW-science-imaging product plot and corresponding product image.

• Example LW-science-imaging product plot and corresponding product image.

Figure caption

Upper Left: Source positions, source fluxes and source fwhm as found by the eclipse peak command.	Upper Right Sky background for each raw frame in counts/pixel. Plot range is +-10% of the background mean.
	Middle Right FWHM histogram of the sources found by the eclipse peak command.
Lower Left: Quality Control and pipeline processing parameters	Lower Right Jitter offset positions as read from the SEQ.CUMOFFSET.X,Y keys of the raw frame stack.

The eclipse command stcube is applied to the coadded product science image.

QC1 parameters

The ISAAC pipeline image recipe is one of the few recipes that applies a source detection algorithm to find a suitable correlation star that must be present in every raw OBJECT frame of the raw frame stack. The images are coadded according the cross-correlation results of this star. (A simpler way would be to coadd the images according to the nominal telescope jitter offsets registered in the fits headers of each raw frame. This simpler method is not suitable in the case of ISAAC). The pipeline recipe coadds only those raw frames, in which the correlation star is found and in which the cross correlation parameter is better than a certain threshold.

QC1 parameters

Early experience has shown that instrumental background features cannot sufficiently be reduced by the pipeline in case the integration time per raw frame is large and the continuous change in paralactic angle is large within the template. Therefore some operational business rules apply.

QC1 parameters

The eclipse command stcube is applied to the coadded product science image and the statistical values are read.

QC1 parameters

A number of environmental parameters are collected. values are read.

QC1 parameters

The ISAAC Hawaii image quality has been compared with Paranal site monitor seeing values. See here.