Quality Control and
Data Processing

HC PLOTS
UVB median dark and rms:
VIS
AGC
NIR remnance:
NIR parameters for DIT=1sec
NIR parameters for DIT=5sec
NIR parameters for DIT=300sec
NIR parameters for DIT=600sec
NIR parameters for DIT=900sec
QC1 database (advanced users): browse | plot

UVB and VIS-arm dark calibrations are acquired as a set of three shutter-closed frames, each one 3600sec (=1h) exposure time. NIR-arm dark calibrations are acquired as a set of three frames coherent in exposure time. Set of frames with low exposure (e.g. DIT=5sec, 10 ...) use three subintegrations (NDIT=3) averaged on the chip, while set of frames with longer exposure times (e.g. DIT=900sec) use NDIT=1.

UVB and VIS dark calibrations are technical calibrations. They are not used to calibrate the science. Their purpose is to monitor the intrinsic dark current of the detector, and radiation not shielded by the detector enclosure, which can be a cosmics and dark level. The same holds for the dark current of the AGC detector

The NIR-arm dark frames are used to calibrate science and standard star observations acquired in STARE mode. Long DIT NIR-arm dark frames rarely suffer from persistence, either induced by a bright arc-lamp exposure or saturation in the K-band. Those dark calibrations are rejected as it is assumed that the persistence is a short period effect.

QC1_parameters

FITS key	QC1 database: table, name	definition	class*	HC_plot**	more docu
QC.MDARKMED	xshooter_dark..median_dark	median value of master dark	HC		[docuSys coming]
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter **There might be more than one.

Trending

For the UVB and VIS arm the dark level is monitored for both read out modes in 1x1 binning. In the long term, the low-gain setup is stable with a larger scatter, while the high-gain setup shows a minor trend. Data from early operations might be biased from from slightly different algorithms used in the early versions in the pipeline.

For the NIR-arm the dark level starts after each detector intervention (warm-up and cool-down of the detector cryostat) at a low value, symptomatically increasing in the long term to a value of about 20 ADU (for DIT=600sec). The NIR-arm dark level is monitored for several DIT values.

The dark of the AGC is not stable.

Scoring&thresholds Dark level

The value is scored. Thresholds are set to operational meaningful values.

History

Date	event
2011-07-07	NIR intervention, as usual for NIR-arm interventions, dark level starts at a low value and increases over months to the pre-intervention value.
2012-07-01	UVB change of dark level for the high gain setup
2017-02-09	the UVB-arm shutter was replaced
2017-05-05	The dome lights were on. In the UVB arm the registered dark level was 0.018 ADU/sec, while it is normally (dome light off) three times lower at 0.0005 ADU/sec. In the VIS arm 0.01 ADU/sec were measured while it is usually 0.001 ADU/sec
2018-01-01	The AGC-arm dark frames are from now on acquired for four DIT only: 10sec, 50sec, 150sec and 300sec.
2018-11-01	The NIR-arm DIT=5sec setup is acquired with NDIT=1, while before is was acquired with NDIT=3. All monitored QC parameters show a slightly different mean level.

Algorithm Dark level

A median stacking method is used to generate a master dark product. The median dark level is the median of the master dark frame.

QC1_parameters

FITS key	QC1 database: table, name	definition	class*	HC_plot**	more docu
QC.MDARKRMS	xshooter_dark..sigma_dark	RMS value of master dark	CAL		[docuSys coming]
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter **There might be more than one.

Trending

For the UVB and VIS arm the dark rms is monitored for both read out modes in 1x1 binning.

The dark rms (the root mean square over all pixel of the master dark) is not monitored for ther NIR-arm and the AGC-arm.

Scoring&thresholds Rms

The rms is not scored.

History

Date	event
2010-06-01	new pipeline version (1.0.0); dark_rms calculated correctly now; results from older versions erased from QC1 database
2010-09-19	- 2010-10-07 typo in pipeline; computation of dark_rms changed , values removed from QC1 database
2011-07-07	NIR intervention

Algorithm Rms

The RMS is the robust root mean square over all pixel of the master dark product.

QC1_parameters

FITS key	QC1 database: table, name	definition	class*	HC_plot**	more docu
QC.MDARK.CONTAM	xshooter_dark..remnance	count difference between region within the redmost echelle order and outside	HC		[docuSys coming]
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter **There might be more than one.

Trending

The QC parameter is for the NIR-arm only.

Scoring&thresholds Remnance

The threshold is 5.5: if this value is above 5 there is a good chance to see remnants from previous high level exposures.

History

Date	event
	NIR darks taken shortly after high flux observations (e.g. flat fields or flux standard stars in twilight) may show remnance in the top orders (raw data) or at right edge (processed data). Below in Fig.A you find an example of a 120s DARK, taken 30 minutes after a bright observations. The cuts are at 23 and 45 counts.
2010-12-05	the VIS CCD got a new cryostat.
2014-01-01	monitoring of the AGC bias level has started

Figure A, NIR-arm remnance in the K-band Echelle orders.

Algorithm Remnance

Remnance gives the difference in flux between the red-most order and the area to its right.

QC1_parameters

FITS key	QC1 database: table, name	definition	class*	HC_plot**	more docu
QC.RON	xshooter_dark..ron	read out noise	HC		[docuSys coming]
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter **There might be more than one.

Trending

The NIR-arm read-out noise is monitored for several DIT values. For UVB and VIS, ron is extracted from Bias frames.

Scoring&thresholds Readout noise

The scoring thresholds are based on statistical grounds.

History

No Remarks.

Algorithm Readout noise

Two NIR-arm raw dark frames are subtracted. The rms of the difference frame within the standard region is the read-out noise.

QC1_parameters

FITS key	QC1 database: table, name	definition	class*	HC_plot**	more docu
QC.CRRATE	xshooter_dark..cosmic_rate	average number of cosmic rays per cm^2 and second	HC		[docuSys coming]
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter **There might be more than one.

Trending

The NIR-arm cosmic rate is monitored for several DIT values. The cosmic rate for the UVB and VIS-arm is registered in the QC1 DB, but not monitored.

Scoring&thresholds Cosmics

The scoring thresholds are based on statistical grounds.

History

Date	event
2010-02-01	The new pipeline version; cosmic_rate calculated slightly differently
2010-09-19	from 2010-09-19 to 2010-10-07 typo in pipeline; computation of cosmic_rate affected, values removed from QC1 database

Algorithm Cosmics

The number of detected cosmic ray hits per surface unit (cm2) and per second.

QC1_parameters

FITS key	QC1 database: table, name	definition	class*	HC_plot**	more docu
QC.NORMFPN	xshooter_dark..fp_norm	fixed pattern amplitude normalized by exposure time	HC		[docuSys coming]
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter **There might be more than one.

Trending

The NIR-arm relative fixed pattern noise is monitored for several DIT values. The fixed pattern noise for the UVB and VIS arm is stored in the QC1 DB, but is not monitored.

Scoring&thresholds Fixed-pattern noise

The scoring thresholds are based on statistical grounds.

History

Date	event
2012-02-10	new pipeline version with different algorithm, and new fp_norm values.
2013-05-01	new pipeline version with different algorithm, and new fp_norm values.

Algorithm Fixed-pattern noise

Fixed pattern noise, scaled to exposure time of 1sec.