Quality Control and
Data Processing

Raw CALIB data types

Find information about the ESPRESSO data format here.

The following calibration data are taken as part of the ESPRESSO 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*
BIAS	CALIB	BIAS	IMAGE	bias structure	10
DARK	CALIB	DARK	IMAGE	hot pixel mask	5
LED FF	CALIB	LED	IMAGE	bad pixel mask	15
ORDERDEF	CALIB	ORDERDEF,LAMP,OFF or ORDERDEF,OFF,LAMP	ECHELLE	order definition	2
FLAT	CALIB	FLAT,LAMP,OFF or FLAT,OFF,LAMP	ECHELLE	blaze function	20
CONTAM	CALIB	CONTAM,OFF,FP OR CONTAM,OFF,THAR	ECHELLE	contamination by reference source	1
WAVE_FP	CALIB	WAVE,FP,FP	ECHELLE	FP wavelength calibtation	1
WAVE_THAR	CALIB	WAVE,THAR,FP or WAVE,FP,THAR	ECHELLE	ThAr wavelength calibration	2
WAVE_LFC	CALIB	WAVE,LFC,FP or WAVE,FP,LFC	ECHELLE	LFC wavelength calibration	2
SKY_FF	CALIB	EFF,SKY,SKY	ECHELLE	relative efficiency between fibres A and B	1
FLUX	CALIB	FLUX,STD,SKY	ECHELLE	flux calibration	1

* N: typical number taken per night and setting

Bias, order definition, spectroscopic flat field, contamination, and wavelength calibration frames are measured daily during daytime as part of the calibration plan. Dark exposures and LED flat fields are measured on a regular basis (daytime) as well as sky flat fields and flux standard stars (night-time).

Three different calibration sources can be used in order to wavelength calibrate ESPRESSO observations: a Fabry-Perot (FP) cavity, ThAr arc lamps, and a laser-frequency comb (LFC). The Fabry-Perot provides more than 60000 lines which are evenly distributed over the entire wavelength range of ESPRESSO. These give a very accurate relative calibration; the absolute wavelength scale has to be determined with ThAr exposures. The LFC on the other hand gives very accurate relative and absolute calibration. It covers, however, not the complete wavelength range of ESPRESSO.

The processing of ESPRESSO 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.