Quality Control and
Data Processing

Raw CALIB data types

Calibration data are taken for two purposes:

• to calibrate SCIENCE data
• to measure and control the instrumental status

The following types of raw calibration data exist for the supported modes:

IMAGING

frame	DPR.CATG	DPR.TYPE	DPR.TECH	purpose
BIAS	CALIB	BIAS	IMAGE	bias level, RON
DARK	CALIB	DARK	IMAGE	dark current
SKY_FLAT_IMG	CALIB	FLAT,SKY	IMAGE	flat field of science data
SCREEN_FLAT_IMG	CALIB	FLAT,LAMP	IMAGE	gain, bad pixel map, lamp efficiency, fixed pattern noise
STANDARD_IMG	CALIB	STD	IMAGE	photometric zeropoints, extinction and colour coefficients

LSS

frame	DPR.CATG	DPR.TYPE	DPR.TECH	purpose
BIAS	CALIB	BIAS	IMAGE	bias level, RON
SCREEN_FLAT_LSS/LAMP_LSS	CALIB	FLAT,LAMP/WAVE,LAMP	SPECTRUM	flat field of science data, slit transfer function, 2D dispersion solution and distortion correction
STANDARD_LSS	CALIB	STD	SPECTRUM	spectrophotometric calibration

MOS/MXU

frame	DPR.CATG	DPR.TYPE	DPR.TECH	purpose
BIAS	CALIB	BIAS	IMAGE	bias level, RON
SCREEN_FLAT_MOS/LAMP_MOS	CALIB	FLAT,LAMP/WAVE,LAMP	MOS	flat field of science data, slit transfer function, 2D dispersion solution and distortion correction
SCREEN_FLAT_MXU/LAMP_MXU	CALIB	FLAT,LAMP/WAVE,LAMP	MXU	flat field of science data, slit transfer function, 2D dispersion solution and distortion correction
STANDARD_MOS	CALIB	STD	MOS	spectrophotometric calibration

PMOS

frame	DPR.CATG	DPR.TYPE	DPR.TECH	purpose
BIAS	CALIB	BIAS	IMAGE	bias level, RON
SCREEN_FLAT_PMOS/LAMP_PMOS	CALIB	FLAT,LAMP/WAVE,LAMP	POLARIMETRY	flat field of science data, slit transfer function, 2D dispersion solution and distortion correction
STANDARD_MOS/PMOS	CALIB	STD	POLARIMETRY	polarimetric calibration

The following types of master calibration data are produced for the supported modes:

IMAGING

frame Type	recipe	description	N	product(s)
BIAS	fors_bias	creates a master BIAS from a set of N input raw frames	5	master BIAS
DARK	fors_dark	creates a master DARK from a set of N input raw frames	5	master DARK
SKY_FLAT_IMG	fors_img_sky_flat	create a master SKY FLAT from set of N input raw frames	3-5	master SKY FLAT
SCREEN_FLAT_IMG	fors_img_screen_flat	create a master SCREEN FLAT from set of N input raw frames	2	master SCREEN FLAT
STANDARD_IMG	fors_zeropoint	reduce STANDARD STAR images and obtain photometric ZEROPOINT of the night	1	reduced image zeropoint table

• Reduced STANDARD star images (PSTI) can be used for own extraction and photometric calibration programmes. They are reduced in the same way as SCIENCE files.
• ZEROPOINT tables (PZPI) contain extracted fluxes and data for these standard stars. They have been produced from reduced standard star images using the tool SExtractor for the flux extraction.

LSS

frame Type	recipe	description	N	product(s)
BIAS	fors_bias	create a master BIAS from set of N input raw frames	5	master BIAS
SCREEN_FLAT_LSS & LAMP_LSS	fors_calib	creates a 2D dispersion solution, correction for spatial distortion, and normalized flat-field	2	normalized master FLAT, dispersion coefficient tables, wavelength map, spatial map
STANDARD_LSS	fors_science	reduce data and apply wavelength correction, correct sky background and extract spectrum	1	extracted spectrum with errors, sky background

MOS/MXU

frame Type	recipe	description	N	product(s)
BIAS	fors_bias	create a master BIAS from set of N input raw frames	5	master BIAS
SCREEN_FLAT_MOS/MXU & LAMP_MOS/MXU	fors_calib	creates a 2D dispersion solution, correction for spatial distortion, and normalized flat-field	2	normalized master FLAT, dispersion coefficient tables, wavelength map, spatial map
STANDARD_MOS	fors_science	reduce data and apply wavelength correction, correct sky background and extract spectrum	1	extracted spectrum with errors, sky background, response and efficiency curves

PMOS

frame Type	recipe	description	N	product(s)
BIAS	fors_bias	create a master BIAS from set of N input raw frames	5	master BIAS
SCREEN_FLAT_PMOS & LAMP_PMOS	fors_pmos_calib	creates a 2D dispersion solution, correction for spatial distortion, and normalized flat-field	2	normalized master FLAT, dispersion coefficient tables, wavelength map, spatial map
STANDARD_PMOS	fors_pmos_science	reduce data and apply wavelength correction, correct sky background and extract spectrum	2-4	extracted spectrum with errors, sky background, polarization parameters

Naming scheme

After production and certification, the calibration products are archived. They are named with a scheme including type, creation date and relevant setting parameters. The master calibrations are available for archive users through the calSelector service.

The processing of FORS2 calibration frames requires a cascaded scheme where the mutual dependencies of products and raw frames are respected. The proper sequence of all these production steps is called the calibration cascade. It is described here.

Within that cascade, all products are checked with respect to their quality and their relationship in time. This means e.g. that a dispersion solution is not only generated using an arbitrary quality-checked localization solution, but that specific solution is chosen which is closest in time.

All products created by QC Garching follow the calibration cascade. On the other hand, Paranal-processed science data use standard solutions created by QC Garching and possibly several months old.

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. Some of them come with different versions indicated by unique , e.g. 140101, of creation, as they are being updated with time.

Table name	PRO.CATG	Purpose
F2_ACAT_<DATE>#_G<GRISM>_<FILT>_S<SLIT>.fits	MASTER_LINECAT	lines catalog
F2_DIST_<DATE>#_G<GRISM>_<FILT>_S<SLIT>.fits	MASTER_DISTORTION_TABLE
F2_GEXT_<DATE>_extinct_table.fits	EXTINCT_TABLE	atmospheric extinction table
F2_GGRS_<DATE>#_G<GRISM>_<FILT>_S<SLIT>.fits	GRISM_TABLE	table with grism parameters
F2_GPHO_<DATE>_<detector>.fits	PHOT_TABLE	table with photometric coefficients for the CCD
F2_GRWC_020331B_retwavechrom.fits	RETARDER_WAVEPLATE_CHROMATISM	table with chromatism information of the retarder wave plate
F2_GSTF_020331B_<std_name>.fits	STD_FLUX_TABLE	table with flux standard star measurements
F2_GSTI_000331B_landolt_std_UBVRI.fits	FLX_STD_IMG	Landolt standard star catalogue (imaging)
F2_GSTI_080401B_stetson_2010Dec09.fits	FLX_STD_IMG	Stetson standard star catalogue (imaging)
F2_GSTP_020331B_pol_sta.fits	STD_PMOS_TABLE
F2_GTLC_020331B_telluric_regions.fits	TELLURIC_CONTAMINATION