Quality Control and
Data Processing

HC PLOTS
Read-out noise
Dark level
Detector temperature
QC1 database (advanced users): browse | plot

One set of DARK frames for the imaging and one for the spectroscopic detector is taken every day during daytime. Each set consists of 10 raw frames and is always obtained with the same instrument setup: detector integration time DET.SEQ1.DIT=0.02s and number of detector sub-integrations DET.NDIT=1000. DARK frames are not used for calibrating science data but are utilized to monitor performance of the VISIR detectors.

	DARK frame of the imaging detector (post-upgrade). Note the different levels for each of the 32 read-out ports.
	DARK frame of the spectroscopic detector (post-upgrade). Note the different levels for each of the 32 read-out ports.

	DARK frame of the imaging detector (pre-upgrade). This is a master DARK frame which was build by averaging 3 raw frames. Note bright horizontal stripes which are characteristic of the pre-upgrade imaging detector. Also visible are clusters of bad pixels.
	DARK frame of the spectroscopic detector (pre-upgrade). This is a master DARK frame which was build by averaging 3 raw frames. Here, characteristic stripes are vertical.

QC1_parameters

FITS key	QC1 database: table, name	definition	class*	HC_plot**	more docu
QC.RON2	visir_dark_img..ron2	read out noise value raw3-raw2	HC		[docuSys coming]
QC.RON2	visir_dark_spc..ron2	read out noise value raw3-raw2	HC		[docuSys coming]
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter **There might be more than one.

Trending

The first dark frame of a stack is sometimes contaminated by transient features that artificially increase the background level and therefore the RON calculation. These features are usually less present in the second and third frames. Therefore, the ron2 parameter (see below) is more stable and is used for trending.

Scoring&thresholds Read-out noise

Scoring thresholds have been set rather losely to 10..20 ADUs due to the uncertainties of the measuring process.

History

April 2015: start of operations after upgrade with new detectors.

Algorithm Read-out noise

Read-out noise is calculated from the difference image of the 2nd - 1st raw frame (for ron1) or of the 3rd - 2nd raw frame (for ron2). It is the median of the standard deviations measured from 100 4x4 windows on the difference frame, multiplied by sqrt(NDIT/2).

QC1_parameters

FITS key	QC1 database: table, name	definition	class*	HC_plot**	more docu
QC.DARKMED	visir_dark_img..darkmed	medium dark level	HC		[docuSys coming]
QC.DARKMED	visir_dark_spc..darkmed	medium dark level	HC		[docuSys coming]
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter **There might be more than one.

Trending

The median dark is trended separately for both the imaging and the spectroscopic detector.

Scoring&thresholds Dark level

Scoring thresholds have been set empirically.

History

April 2015: start of operations after upgrade with new detectors.

Algorithm Dark level

The median dark level is calculated in the central part of the master dark.

QC1_parameters

FITS key	QC1 database: table, name	definition	class*	HC_plot**	more docu
INS.TEMP30.VAL	visir_dark_img..ins_sens30_val	temperature of the imager detector	ENG		[docuSys coming]
INS.TEMP31.VAL	visir_dark_spc..ins_sens31_val	temperature of the spectro det.	ENG		[docuSys coming]
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter **There might be more than one.

Trending

The detector temperature is trended separately for both the imaging and the spectroscopic detector.

Scoring&thresholds Detector temperature

Scoring thresholds have been set according to the operational values for the detector temperature.

History

2010-05-12: the temperature of the imaging detector is read from keyword INS.TEMP30.VAL and of the spectroscopic detector from keyword INS.TEMP31.VAL. Before that date different keywords were used: INS.SENS30.VAL and INS.SENS31.VAL, respectively. The names of the QC1 database columns remained unchanged.
2015-04-12: start of Service Mode observations with new detectors.

Algorithm Detector temperature

Values as recorded in the header keys INS.TEMP30.VAL and INS.TEMP31.VAL.