Quality Control and
Data Processing

HC PLOTS
Number of bad pixels
Flat-field flux
QC1 database (advanced users): browse | plot

Flat-field frames are not measured any longer after the instrument upgrade. The information on this page refers to the pre-upgrade status until May 2012 and is kept here for historical reference.

One set of flat-field exposures is taken daily during daytime. It consists of up to 6 raw frames, where each is illuminated with different flux level. The changes of the flux are achieved by illuminating the detector with the Warm Calibration Unit which simulates black body radiation with different temperatures:

• 1st frame: 20 C (keyword INS.EXTS.ACT)
• 2nd frame: 10 C
• 3rd frame: 0 C
• 4th frame: -10 C
• 5th frame: -20 C
• 6th frame: -30 C

	FLAT FIELD master frame of the imaging detector (pre-upgrade). This is a pipeline product of the visir_img_ff recipe. It was build by combining the 6 input raw frames. Note bright horizontal stripes which are characteristic for the pre-upgrade detector.
	FLAT FIELD 2nd raw frame (pre-upgrade). This is a 2nd raw FLAT FIELD frame which corresponds to the illumination by the black body with temperature of 10 C.

QC1_parameters

FITS key	QC1 database: table, name	definition	class*	HC_plot**	more docu
QC.NBBADPIX	visir_flat_img..nbbadpix	number of bad pixels	HC		[docuSys coming]
QC.NBBADPIX	visir_flat_spc..nbbadpix	number of bad pixels	HC		[docuSys coming]
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter **There might be more than one.

Trending

The number of bad pixels was trended separately for both the imaging and the spectroscopic detector.

Scoring&thresholds Bad pixels

Scoring is not implemented.

History

May 2012: end of operations new detectors, flat fields are no longer measured.

Algorithm Bad pixels

The median intensity is determined determined for each flat-field image. Then a linear fit of the actual intensity per pixel and the median is achieved. Those pixels where the slope (i.e. relative gain) deviates strongly from 1, i.e. the relative gain is outside the range of 1/5 to 5, are flagged as bad pixels.

QC1_parameters

FITS key	QC1 database: table, name	definition	class*	HC_plot**	more docu
QC.LAMPFLUX	visir_flat_img..lamp_flux	lamp flux per DIT	CAL		[docuSys coming]
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter **There might be more than one.

Trending

The flat-field flux was trended for the imaging detector.

Scoring&thresholds Bad pixels

Scoring is not implemented.

History

May 2012: end of operations new detectors, flat fields are no longer measured.

Algorithm Bad pixels

This parameter monitors the stability of the Warm Calibration Unit (WCU). The first two flat-field frames in the stack (taken at temperatures 20C and 10C of the WCU) are subtracted from each other, the median flux in the central area is calculated, and normalized by DIT.