Quality Control and
Data Processing

RAW CALIBRATION DATA

Calibration data for VIRCAM are taken for two purposes:

• assess the instrument status
• reduce science data

Generally, VIRCAM calibration data are taken as daytime calibrations.

The calibration data taken are processed by QC Garching to obtain calibration solutions. These solutions come as:

• calibration product FITS file frames (e.g. master DARK or master twilight flat frames)
• calibration product FITS tables (e.g. linearity correction table, gain table)

Frame Type	DPR.TYPE	Purpose
RESET	BIAS	monitor the Uncorr read mode (reset-read)
DOME FLAT	FLAT,LAMP	monitor flat field cosmetics
DARK CURRENT	DARK,CURRENT	monitor dark current ( ADU/sec )
LINEARITY	FLAT,LAMP,LINEARITY DARK,LINEARITY FLAT,LAMP,CHECK DARK,CHECK	calibrate the detector non-linearity, retrieve bad pixel
GAIN	FLAT,LAMP,GAIN DARK,GAIN	extract detector gain
DARK	DARK	calibrate the dark level and , hot pixel
TWILIGHT FLAT	FLAT,TWILIGHT	calibrate fixed pattern noise
STD	STD,FLUX	monior the instrumental throughput

Among others, the following types of master calibration data are produced using the vircam data reduction pipeline. Only those calibrations are listed, which are certified and ingested into the archive:

Frame Type	recipe	Description	product code	N
MASTER_BIAS	vircam_reset_combine	master bias frame	VC_MRST	5
MASTER_DOME_FLAT	vircam_dome_flat_combine	master dome flat	VC_MDOF	5
MASTER_DARK_CURRENT	vircam_dark_current	retrieve dark current	VC_MDCT	14
MASTER_CHANNEL_TABLE MASTER_BPM	vircam_linearity_analyse	non-linearity correction	VC_MCHT VC_MBPM	79
MASTER_READGAIN_TABLE	vircam_detector_noise	detector gain	VC_PRGT	4
MASTER_DARK	vircam_dark_combine	dark level, hot pixel	VC_MDRK	5
MASTER_TWILIGHT_FLAT MASTER_CONF	vircam_twilight_flat_combine	flat fielding	VC_MTWF VC_PCFM	20
JITTERED_IMAGE_STD OBJECT_CATALOGUE_STD CONFIDENCE_MAP_STD ILLCORR_TAB_STD	vircam_standard_process	photometric zeropoint	VC_PJTI VC_POJC VC_PCFM	5

Like for nearly all astronomical data, the reduction of VIRCAM calibration frames requires a cascading scheme where the mutual dependencies of products and raw frames have to be respected. The MASTER_CHANNEL_TABLE can be produced from raw files only, but all the other products require the prior generation of other calibration products. The proper sequence of all these production steps is called the calibration cascade.

Static calibration tables (the ones not being regularly processed from raw calibration data) come as FITS tables and are available through the calSelector archive service.

product name	PRO.CATG	Purpose
VC_GCTI_<yymmdd>A_Z.fits	CHANNEL_TABLE_INIT	detector register definition, initial gains
VC_GMMC_<yymmdd>A.fits	MASTER_2MASS_CATALOGUE	root file of the 2MASS photometric and astrometric catalogue
VC_GPCT_<yymmdd>A.fits	PHOTCAL_TAB	color coefficients, color terms
VC_GCSN_<yymmdd>A.fits	SCHLEGEL_MAP_NORTH	interstellar extinction map
VC_GCSS_<yymmdd>A.fits	SCHLEGEL_MAP_SOUTH	interstellar extinction map