Quality Control and
Data Processing

HC PLOTS
imaging lamps
QC1 database (advanced users): browse | plot
spectroscopic lamps
QC1 database (advanced users): browse | plot

This page refers to the determination of linearity and gain by the DETMON recipe from the dedicated (TPL.ID=FORS2_img_tec_detLin) calibrations. Conversion factor derived traditionally from imaging SCREEN FLATS by the fors pipeline can be found here.

The flux of the lamps used for imaging, FlatBlue+1 and FlatBlue+2, is monitored based on the imaging screen flats.

QC1_parameters

FITS key	QC1 database: table, name	definition	class*	HC_plot**	more docu
QC.FLAT.EFF	fors2_scrflat..efficiency	lamp efficiency	HC		[docuSys coming]
[Calculated by QC procedure]	fors2_scrflat..sigma_master	sigma of master screenflat (relative)			[docuSys coming]
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter **There might be more than one.

Trending

The flux of the imaging lamps is trended here for different filters. Also, the RMS is trended here. Only data obtained with binning 2x2 and standard resolution collimator are trended.

Scoring&thresholds Imaging Lamps

The flux of the FlatBlue+1 and FlatBlue+2 lamps is very stable. It is loosely scored with constant thresholds. The only requirement is stability on the calibration timescale.

History

Date	event
2010-12-01	FlatBlue+1 lamp replaced
2010-11-04	new FlatBlue+1 lamp saturates imaging screen flats
2010-10-19	FlatBlue+1 lamp replaced
2010-08-25	FlatBlue+1 lamp replaced

Trending of the old FORS2 CCD (until 2002-03-31):

• April-June 2000
• July-September 2000
• October-December 2000
• January-March 2001
• April-June 2001
• July-September 2001
• October-December 2001
• January-March 2002

Algorithm Imaging Lamps

The lamp efficiency is the median signal of the first raw frame devided by exposure time. The median value is computed within a window 250x150 pixel chosen close to the gap region between the 2 CCDs to minimize the illumination gradient. This is only a nominal 'efficiency' actually measuring the stability of exposure level (influenced by e.g. aging of lamps etc.).

The RMS (sigma_master) is calculated from the master screen flat image pixel sample (2x2 binning) X: @200 @1800 and Y: @400 @800 covering the unvignetted area of chip1 and chip2.

The flux of the lamps used for spectroscopy (both flat and arcs) is monitored based on dedicated, daily lamp exposures (LAMP_CHECK).

Spectroscopic lamps:

• FlatBlue+3 and FlatBlue+4: the two high brightness blue halogen lamps used to generate spectroscopic flats in blue (G300V, G600B) spectroscopic setups; On April 18, 2016 the FlatBlue+4 lamp was disabled
• FlatRed+3 and FlatRed+4: the two red halogen lamps used to generate spectroscopic flats in red spectroscopic setups
• Ar+1 and Ar+2 arc lamps
• He+1 arc lamp
• HgCd+2 arc lamp
• Ne+1 and Ne+2 arc lamps

QC1_parameters

FITS key	QC1 database: table, name	definition	class*	HC_plot**	more docu
QC.LAMP.FLUX	fors2_lamp_chk..flux	Summed Flux per second (ADU/s)	HC		[docuSys coming]
QC.LAMP.FLUXERR	fors2_lamp_chk..fluxerr		HC		[docuSys coming]
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter **There might be more than one.

Trending

For trending we use only data obtained with the 300V grism with the GG435 filter and a 1" slit, using the standard resolution collimator.

In particular, monitoring of the lamp flux of the two high brightness blue halogen lamps FlatBlue+3 and FlatBlue+4, used to generate spectroscopic flats in blue (G300V, G600B) spectroscopic setups is performed. On April 18, 2016 the FlatBlue+4 lamp was disabled and later taken out of the instrument's calibration unit. Since then, only FlatBlue+3 lamp is used for spectroscopic flats. On November 15, 2016 the sub-plots relevant to the FlatBlue+4 lamp were removed.

Scoring&thresholds Spectroscopic Lamps

The flux of the spectroscopic lamps is tightly scored with constant thresholds. This is to ensure flux stability (to detect moments when lamp needs to be replaced) and to avoid possible saturations and underexposition. The requirement is stability on the calibration timescale.

History

Date	event
2010-12-01	FlatBlue+1 lamp replaced
2010-10-19	FlatBlue+1 lamp replaced
2010-08-25	FlatBlue+1 lamp replaced
2010-02-11	Exposure times for FlatBlue+4 were reduced by 20%, thresholds were accordingly raised by 25%
2014-01-10	FlatBlue+3/4 lamps were replaced
2014-05-16	FlatBlue+3 lamp exchanged (PPRS-056400)
2014-05-17	FlatBlue+4 lamp exchanged (PPRS-056425)
2014-12-15	FlatBlue+3 lamp exchanged (PPRS-059326)
2015-02-28	FlatBlue+3/+4 lamps exchanged
2015-03-02	Exposure times for FlatBlue+3/+4 were doubled, thresholds were accordingly reduced by 50%
2015-08-29	Ne+2 lamp exchanged
2015-10-30	FlatBlue+4 lamp exchanged
2016-04-18	To stabilize the FORS2 ECU, the FlabBlue+4 lamp was disabled and removed; Since then, only lamp FlatBlue+3 has been used for spectroscopic flats.
2016-05-14	FlatBlue+3 lamp was found off; replaced (PPRS-065344)
2016-08-06	FlatBlue+3 lamp was replaced (PPRS-066194)
2016-10-05	FlatBlue+3 lamp was replaced (PPRS-066717)
2016-10-11	FlatBlue+3 lamp was replaced again; at that time the FlatRed+4 lamp got moved and had to be re-adjusted (PPRS-066771)
2016-10-24	FlatBlue+3 lamp was exchanged; The iris of the ECU blue section was moved to adjust the flux (PPRS-066859)
2016-11-15	HC plot modified; the sub-plots relevant to the FlatBlue+4 lamp were removed
2016-12-23	FlatBlue+3 lamp was replaced (PPRS-067451)
2017-01-10	FlatBlue+3 lamp was replaced (PPRS-067612)
2017-03-04	FlatBlue+3 lamp was replaced (PPRS-068113)
2017-04-27	FlatBlue+3 lamp was exchanged and aligned (PPRS-068682)
2017-05-25	FlatBlue+3 lamp was replaced (PPRS-068976)
2017-06-23	FlatBlue+3 lamp was replaced (PPRS-069290)
2017-07-05	FlatBlue+3 lamp was replaced (PPRS-069387)
2017-09-10	FlatBlue+3 lamp was replaced (PPRS-070214)
2017-09-25	FlatBlue+3 lamp was replaced (PPRS-070264)
2017-09-25	Following request from Paranal, threshold for the flux of the HgCd lamp was increased by 0.7 for both chips
2017-11-25	FlatBlue+3 lamp was replaced (PPRS-070901)
2018-01-29	FlatBlue+3 lamp was replaced and realigned (PPRS-071446)
2018-02-05	FlatBlue+3 lamps were replaced and adjusted (PPRS-071491)
2018-03-20	FlatBlue+3 lamp was replaced (PPRS-071972)
2018-04-05	FlatBlue+3 lamp replaced and aligned (PPRS-072113)
2018-04-23	FlatBlue+3 lamp replaced and aligned (PPRS-072309)
2018-05-04	FlatBlue+3 lamp replaced and aligned (PPRS-072425+072436)
2018-07-03	FlatBlue+3 lamp replaced and aligned (PPRS-073065)
2018-08-20	FlatBlue+3 lamp replaced and aligned (PPRS-073496)
2018-08-24	FlatBlue+3 lamp found in error state; replaced and aligned (PPRS-073545)
2018-08-30	Flux of the Ne+2 lamp decreased but is still sufficient and stable; thresholds were lowered by ~5%
2018-11-04	FlatBlue+3 lamp adjusted; flux within thresholds (PPRS-074283)
2019-03-01	new FlatBlue+3 lamp holder and new lamp were installed; flux was adjusted (PPRS-075402)
2019-03-01	FlatRed+4 lamp was exchanged and flux was adjusted (PPRS-075408)
2019-03-10	FlatBlue+3 lamp was exchanged (PPRS-075484)
2019-05-15	FlatBlue+3 lamp was adjusted (PPRS-076092)
2019-07-04	FlatBlue+3 lamp was exchanged (PPRS-076511)
2019-07-08	new FlatBlue+3 lamp and lamp holder were installed (PPRS-076538)
2019-07-30	FlatBlue+3 lamp was exchanged (PPRS-076720)
2019-08-04	FlatBlue+3 lamp was exchanged (PPRS-076793)
2020-09-25	FlatBlue+3 lamp was exchanged (PPRS-079159)
2020-10-16	FlatBlue+3 lamp was exchanged (PPRS-079236)
2021-02-28	FlatBlue+2 lamp was exchanged (PPRS-080257)

Algorithm Spectroscopic Lamps

Th lamp flux is determined from a bias-subtracted calibration lamp exposure in LSS mode. After background subtraction the total signal is integrated and normalized by the exposure time and the total number of original CCD pixels (keeping into account possible binning). The background is evaluated from the available overscan regions.