VISIR pipeline: processing of calibration data

VISIR pipeline:
calibration data

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VISIR CALIBRATION DATA: GENERAL

Calibration data for VISIR are taken for two purposes:

to assess the instrument status
to reduce science data

VISIR calibration data are taken at night (e.g. standard star observations) and as daytime calibrations (flatfield). On request of the user, also nighttime calibrations can be obtained as part of the Observing Block which generates the SCIENCE data ("attached calibrations").

All calibration data taken in VISIR are processed by QC Garching to obtain calibration solutions. These solutions come as

calibration product fits file frames (e.g. standard star imaging frames)
calibration product fits tables (e.g. spectrum extracted in a form of a table)

TYPES OF RAW CALIBRATION DATA

FITS header examples
frame	.txt
IMG FLAT
SPEC FLAT
IMG STD
SPEC STD

The following types of raw calibration data exist for the VISIR:

frame DPR TYPE Purpose
typical number taken per night and setting

IMG FLAT FLAT fixed pattern noise, gain, bad pixel map
7 x each filter/lens combination

SPEC FLAT FLAT fixed pattern noise, gain, bad pixel map
7 x each instr. combination

IMG STANDARD STAR STD standard stars for imaging varies

SPEC STANDARD STAR STD standard stars for telluric features varies

CALIBRATION PRODUCTS

	calibration recipes
	naming scheme

Recipes and products

The following VISIR calibration products are created from raw calibration files (click here for a complete overview of calibration files and recipes):

raw frame(s)	template/recipe	description	products, PRO.CATG
IMG FLAT	VISIR_img_cal_ExtSrcFlats visir_img_ff	creates a master flatfield for the imaging detector from a set of 7 input raw frames taken at different temp. of the WarmCalibrationUnit	IMG_FF IMG_BPM
SPEC FLAT	VISIR_spec_cal_ExtSrcFlats visir_spc_ff	creates a master flatfield for the spectroscopic detector from a set of 7 input raw frames taken at different temp. of the WarmCalibrationUnit	SPEC_FF SPEC_BPM
IMG STD	VISIR_img_cal_AutoChopNod visir_img_phot	determines observing conditions, instrumental respons, senistivity, background, etc.	IMG_PHOT_COMBINED IMG_PHOT_CONTRIB_MAP
SPEC STD	VISIR_spec_cal_LRAutoChopNod visir_spc_phot	telluric standard, determines observing conditions, instrumental respons, senistivity, etc.	SPC_PHOT_COMBINED SPC_PHOT_TAB SPC_PHOT_WEIGHT

Naming scheme

After production and certification, the calibration products are renamed after a scheme which includes type, creation data and relevant VISIR setting. .

CALIBRATION CASCADE

At present, all sets of VISIR calibration frames are reduced independently, i.e. there is no calibration cascade. In the future the flatfield correction may be included. It's still under investigation.

OTHER CALIBRATION TABLES

Static calibrations include a reference arc line table and a quantum efficiency map

ACTUAL PROBLEMS AND ISSUES

VISIR Pipeline problems are documented under on the ServiceMode page.