Quality Control and
Data Processing

Raw CALIB data types

Find information about the GRAVITY data format here.

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

frame	DPR.CATG	DPR.TYPE	DPR.TECH	purpose	N*
DARK	CALIB	DARK	IMAGE,DIRECT or IMAGE,WOLLASTON	dark current; detector bad pixels	1
FLAT	CALIB	FLAT	SPECTRUM,DIRECT or SPECTRUM,WOLLASTON	localization of spectra; bad pixels	4
WAVE	CALIB	WAVE	INTERFEROMETRY,DIRECT or INTERFEROMETRY,WOLLASTON	wavelength calibration	1
	CALIB	WAVE,SC	INTERFEROMETRY,DIRECT or INTERFEROMETRY,WOLLASTON	wavelength calibration	1
P2VM	CALIB	P2VM	INTERFEROMETRY,DIRECT or INTERFEROMETRY,WOLLASTON	pixel-to-visibility matrix	6
STD	CALIB	STD,SINGLE	INTERFEROMETRY,DIRECT or INTERFEROMETRY,WOLLASTON	calibrator	2
	CALIB	SKY,SINGLE	SPECTRUM,DIRECT or SPECTRUM,WOLLASTON	sky exposure for calibrator	1
STD	CALIB	STD,DUAL	INTERFEROMETRY,DIRECT or INTERFEROMETRY,WOLLASTON	calibrator	2
	CALIB	SKY,DUAL	SPECTRUM,DIRECT or SPECTRUM,WOLLASTON	sky exposure for calibrator	1

* N: typical number taken per night and setting

Dark, flat-field, wavelength, and P2VM calibrations are measured during daytime as part of the calibration plan. They are taken separately for each of the six combinations of spectral resolution (low, medium, or high) and polarimetry mode (splitted or combined). Astronomical calibrators are measured during night-time, typically in a SCI-CAL or CAL-SCI-CAL sequence.

The processing of GRAVITY 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.