Quality Control and
Data Processing

Raw CALIB data types

GIRAFFE calibration data are mostly taken as daytime calibrations. Flux standard stars and nasmyth screen flats are taken, as part of the calibration plan, for Argus data. Find information about the GIRAFFE data format, spectral format and the detector here. The following calibration data are taken as part of the daily GIRAFFE 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	detector status, bias level	5
DARK	CALIB	DARK	IMAGE	dark current (for maintenance); CCD glow (old CCD only)	3
FLAT (taken with the calibration lamp on the robot arm; this is the regular flat also called 'robotic' flat)	CALIB	LAMP,FLAT	MOS (for Medusa) or IFU (for IFU and Argus)	signal localization and extraction; fix-pattern noise, fringing	3
FLAT (taken with the nasmyth screen illuminated; this is the 'attached' flat taken during the night, useful for Argus mode because of better illumination)	CALIB	LAMP,FLAT,NASMYTH	MOS (for Medusa) or IFU (for IFU and Argus)	same as FLAT	3
IMAGE FLAT	CALIB	LAMP,FLAT,DETCHECK	IMAGE	detector monitoring	40
ARC-LAMP	CALIB	LAMP,WAVE	MOS (for Medusa) or IFU (for IFU and Argus)	dispersion relation, wavelength calibration, resolution monitoring	1
STD (flux standard star, taken for Argus data)	CALIB	STD	IFU (argus)	relative flux calibration	1

*N: typical number taken per night and setting

The ARC-LAMP and FLAT frames split into five fibre system (MEDUSA1/2; IFU1/2; Argus). They also split into two different gratings (HR and LR) with a set of standard wavelengths (which are listed here).

BIAS frames are taken in unbinned (1x1) mode, normal, high or low gain.

The flux STD data are regularly taken for the Argus and IFU settings.

In addition, DARK frames are taken about monthly, to monitor the dark current level.

A series of about 40 IMAGE FLATs is also taken roughly once per month, to monitor the status of the detector. They come in pairs with exposure times increasing from 0 to about 280 sec (saturation). Both types of data are not required for science reduction.

Overview of calibration files and recipes

* for STD_ARG data ony; for STD_IFU data, no instrument response is produced.

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 GIRAFFE 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.

Table name	PRO.CATG	Purpose
GI_GRAT_040813A_HR_grating.fits, GI_GRAT_030412A_LR_grating.fits	GRATING_DATA	grating table: definition of setups per grating; high resolution grating (316 lines/mm) and low resolution grating (600 lines/mm)
GI_GCAT_040421A_line_catalog.fits	LINE_CATALOG	Thorium argon line table: wavelengths, identifications and fluxes used for wavelength calibration
GI_GSGS_041207A_Medusa1_H379.0nm_o15.fits (name is an example)	SLIT_GEOMETRY_SETUP	slit geometry table: describes fibre and button parameters per slit
GI_GDIS_030610A_Medusa2_H737.nm_o8.fits (name is an example)	REFERENCE_DISP_SOLUTION	reference dispersion solution, used by the pipeline as starting point for fine-tuned solution
GI_GMSK_050327A_H572.8nm_o10.fits (name is an example)	LINE_MASK	table with initial guesses for emission lines
GI_GFLX_021231A_flux_standards.fits	FLUX_STANDARDS	list of flux standards
GI_GATM_021231A_atm_extinction.fits	ATMOSPHERIC_EXTINCTION	table with extinction