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VISIR:
calibration data

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CALIBRATION DATA: GENERAL

Calibration data are taken for two purposes:

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

VISIR calibration data are taken as night-time and daytime calibrations. Only night-time measurements (e.g. standard stars) are normally used to calibrate science data.

TYPES OF RAW CALIBRATION DATA

Find information about the VISIR data format and the detector here.

The following calibration data are taken as part of the VISIR calibration plan. The data types are identified by the DPR keyword in the FITS headers.

frame DPR.CATG DPR.TYPE DPR.TECH purpose N* details
DARK CALIB DARK IMAGE
SPECTRUM
read-out noise, dark current 3  
FLAT
CALIB FLAT
IMAGE,DIRECT
SPECTRUM,DIRECT
pixel-to-pixel variation of gain, bad pixels 4-7
STD IMG CALIB STD IMAGE,CHOPNOD sensitivity, conversion factor, mean background 2 [ STD example frame ] 
STD SPC CALIB STD SPECTRUM,CHOPNOD telluric correction, flux calibration, sensitivity 2 [ STD example frame ] 
STD ECH CALIB STD ECHELLE telluric correction, flux calibration, sensitivity 2  

* N: typical number taken per night and setting

CALIBRATION PRODUCTS (pre-upgrade)

As reference, the calibration products that have been created with the pre-upgrade pipeline and that have been distributed in Service Mode packages until September 2011 are described here.

arrow Complete overview of (pre-upgrade) calibration files and recipes

Raw frame(s) recipe description product(s) [PRO.CATG header keywords]
dark [visir_dark_img.png 3K] visir_img_dark creates a master dark from a set of input raw frames of the imaging detector IMG_DARK_AVG
dark [visir_dark_spc.png 3K] visir_img_dark creates a master dark from a set of input raw frames of the spectroscopic detector SPEC_DARK_AVG
flat field [visir_flat_img.png, 2K] 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
IMG std [visir_std_img.png, 2K]

visir_img_phot

determines sensitivity, background, conversion factor, instrumental response, observing conditions, etc. IMG_PHOT_COMBINED
IMG_PHOT_CONTRIB_MAP
SPEC LR/MR/HR-slit std [visir_std_spec.png, 2K]

visir_spc_phot

determines sensitivity, background and conversion factor as a function of wavelength, instrumental response, observing conditions, sky spectrum, etc. SPC_PHOT_COMBINED
SPC_PHOT_TAB
SPC_PHOT_WEIGHT
SPEC ECHELLE std [visir_std_ech.png, 2K]

visir_spc_phot_ech

determines sensitivity, background and conversion factor as a function of wavelength, instrumental response, observing conditions, sky spectrum, etc. SPC_PHOT_HRG_COMBINED
SPC_PHOT_HRG_TAB
SPC_PHOT_HRG_WEIGHT

Naming scheme

After production and certification, the calibration products are renamed with a more user-friendly scheme which includes type, creation date and relevant setting parameters.

arrow Description of naming scheme


 
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