Quality Control and
Data Processing

RAW CALIBRATION DATA

Calibration data for XSHOOTER are taken for two purposes:

• assess the instrument status
• reduce science data

Generally, XSHOOTER calibration data are taken as daytime calibrations. Please, refer to Chapter 4 of the XSHOOTER User Manual for details on the current calibration plan.

The calibration data taken obtained in the supported modes are processed by QC Garching to obtain calibration solutions. These solutions come as:

• calibration product FITS file frames (e.g. master BIAS or FLATFIELD frames)
• calibration product FITS tables (e.g. updated configuration tables)

Frame Type	DPR.TYPE	DPR.TECH	Purpose
LINEARITY_UVB/VIS	BIAS,DETCHECK FLAT,LINEARITY,DETCHAR	IMAGE	gain, non-linearity, bad pixel map
LINEARITY_NIR	FLAT,LINEARITY,DETCHAR	IMAGE	gain, non-linearity, bad pixel map
BIAS_<arm>	BIAS	IMAGE	bias level, ron
DARK_<arm>	DARK	IMAGE	dark current, ron
FMTCHK_<arm>	LAMP,FMTCHK	ECHELLE,PINHOLE	check spectral format
ORDERDEF_<arm>	LAMP,ORDERDEF	ECHELLE,PINHOLE	order detection
WAVE_<arm>	LAMP,WAVE	ECHELLE,MULTI-PINHOLE	optical distortion
FLAT_SLIT_<arm>	LAMP,FLAT	ECHELLE,SLIT	order edges, flat fielding
FLAT_IFU_<arm>	LAMP,FLAT	ECHELLE,IFU	order edges, flat fielding
ARC_SLIT_<arm>	LAMP,WAVE	ECHELLE,SLIT	line tilt, resolution
ARC_IFU_<arm>	LAMP,WAVE	ECHELLE,IFU	line tilt, resolution
FLEX_SLIT_<arm>	LAMP,AFC	ECHELLE	flexure compensation
FLEX_IFU_<arm>	LAMP,AFC	ECHELLE	flexure compensation
STD_TELL_SLIT_STARE	STD,TELLURIC	ECHELLE,SLIT,STARE	correction of
STD_TELL_SLIT_NOD	STD,TELLURIC	ECHELLE,SLIT,NOD	telluric absorption
STD_TELL_IFU_STARE	STD,TELLURIC	ECHELLE,IFU,STARE	features in science spectra
STD_FLUX_SLIT_NOD	STD,FLUX	ECHELLE,SLIT,NOD	spectro-
STD_FLUX_SLIT_OFF	STD,FLUX STD,SKY	ECHELLE,SLIT,OFFSET	photometric
STD_FLUX_IFU_OFF	STD,FLUX STD,SKY	ECHELLE,IFU,OFFSET	calibration

Notes:
In UVB two lamps are used, a D2 and a quartz lamp (LAMP,DORDERDEF+LAMP,QORDERDEF and LAMP,DFLAT+LAMP,QFLAT)
For the NIR arm there is also an OFF frame for every ON frame with DPR.TECH=IMAGE.

The following types of master calibration data are produced for the supported modes:

Frame Type	recipe	Description	N	Products
LINRAERITY_<arm>	detmon_opt/ir	gain, non-linearity, bad pixel map	37/22	bad pixel map, table with gain and non-linearity
BIAS_<arm>	xsh_mbias	create master bias	5	master bias, bad pixel map
DARK_<arm>	xsh_mdark	create master dark	3	master dark, bad pixel map
FMTCHK_<arm>	xsh _predict	spectroscopic format	1	format table
ORDERDEF_<arm>	xsh_orderpos	order detection	1	order center table
FLAT_SLIT_<arm>	xsh_flat	flat fielding	5/10	master flat, order egdes table
FLAT_IFU_<arm>	xsh_flat	flat fielding	5/10	master flat, order egdes table
WAVE_<arm>	xsh_2dmap	distortion coefficients	1	updated config table, wave map, slit map, distortion coefficients
ARC_SLIT_<arm>	xsh_wavecal	line tilts, spectral resolution	1	with line tilt and spectral resolution
ARC_IFU_<arm>	xsh_wavecal	line tilts, spectral resolution	1	with line tilt and spectral resolution
FLEX_SLIT_<arm>	xsh_flexcomp	determine shift between observed	1	table with shift
FLEX_IFU_<arm>	xsh_flexcomp	and predicted line position	1	table with shift
STD_TELL_SLIT_STARE	xsh_scired_slit_stare	{ process	1	{ flux calibrated
STD_TELL_SLIT_NOD	xsh_scired_slit_nod	standard star spectrum	2	telluric standard
STD_TELL_IFU_STARE	xsh_scired_ifu_stare	like science data }	1	star spectrum }
STD_FLUX_SLIT_NOD	xsh_respon_slit_nod	{ process flux std	2	efficiency, response function
STD_FLUX_SLIT_OFF	xsh_respon_slit_offset	for efficiency and	2	efficiency, response function
STD_FLUX_IFU_OFF	xsh_respon_ifu_offset	response function }	2	efficiency, response function

Notes:
For the NIR arm calibrations with lamps, there is also an OFF frame for every ON frame
In UVB two lamps are used, a D2 and a quartz lamp

Like for all astronomical data, the reduction of XSHOOTER calibration frames requires a cascading scheme where the mutual dependencies of products and raw frames have to be respected. Master Biases and DARKs can be produced from raw files only, but all the other products require the prior generation of other calibration products. The proper sequence of all these production steps is called the calibration cascade.

The XSHOOTER calibration plan is subject of improvemements.

Date	event
2009-10-18	Start of operations
2010-01-08	The calibration plan includes now the regular acquisition of flux standard stars in offset mode (one object and one sky frame).
2010-04-01	XSHOOTER fits file names have a new prefix. It changed from SHOOT to XSHOO.
2011-05-02	flux standard stars are acquired in nodding mode (two object frames). Before flux standard stars have been take in offset mode (one object and one sky frame).
2013-04-01	The calibration plan concerning telluric standard stars is changed. From now on telluric standard stars are acquired in nodding mode with two frames per template. Before telluric standard stars have been acquired in stare mode with only one raw frame.
2013-10-01	DFO: Telluric standard star association blocks contain a response function to be flux calibrated.
2015-04-01	science and telluric standard star spectra are calibrated using the individual response curve derived from the closest in time flux standard star. Before a master response curve was used.
2018-04-01	The calibration plan concerning telluric standard stars is changed. While before telluric standard stars have bee acquired for every science OB within +- 2 hours and within +-0.1 aim mass difference, one telluric standard star is from now on taken once a time in a night. The nodding template takes several exposures covering all available slit widths, including the 5'' slit.

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.

product name	PRO.CATG	Purpose
XS_GBPM_<yymmdd>A_<arm>_<binning>.fits	BP_MAP_RP_<arm>	static bad pixel map
XS_GSFT_<yymmdd>A_<arm>_>slit>.fits	SPECTRAL_FORMAT_TAB_<arm>	order definition
XS_GSLL_<yymmdd>A_<arm>.fits	SKY_LINE_LIST_<arm>	list of sky lines
XS_GEXT_<yymmdd>A_<arm>.fits	ATMOS_EXT_<arm>	atmospheric extinction table
XS_GRFP_<yymmdd>A_<arm>.fits	RESP_FIT_POINTS_CAT_<arm>	response function fit points
XS_GSFT_<yymmdd>A_<arm>.fits	FLUX_STD_CATALOG_<arm>	absolute fluxes of standard stars
XS_GTMC_<yymmdd>A_<arm>.fits	TELL_MOD_CAT_<arm>	telluric models for flux std

Notes:
There is one SPECTRAL_FORMAT_TAB_UVB and one SPECTRAL_FORMAT_TAB_VIS for all slits. Only for the NIR arm, which ignores two orders for the two K-band suppressing slits, the SPECTRAL_FORMAT_TAB_NIR splits up per slit.
There is no TELL_MOD_CAT_UVB, no telluric correction is required to derive the response function in the UVB arm.