Quality Control and
Data Processing

HC PLOTS
throughput
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std_throughput
QC1 database (advanced users): browse | plot

The MUSE instrument throughput is estimated in two ways: from the daily technical calibrations comparing number of photons detected on the channels (each slice) with the amount generated by photodiodes located in front of the instrument, and from the spectrophotometric observations of standard stars.

Throughput data are technical calibrations taken daily in two instrument setups: INS.MODE=WFM-NOAO-E, INS.OPTI1.NAME=Clear, DET.READ.CURNMAE=SCI1.0, and INS.MODE=WFM-NOAO-N, INS.OPTI1.NAME=Blue, DET.READ.CURNMAE=SCI1.0. Their purpose is to monitor MUSE throughput by comparing amount of photons generated by photodiode 2 and 1, located in front of the instrument (calibration unit), with amount detected on the channels (each slice).

QC1_parameters

FITS key	QC1 database: table, name	definition	class*	HC_plot**	more docu
QC.AMPL.THRU1	muse_throughput..thru1	[%] Channel throughput compared to photodiode 1	HC		[docuSys coming]
QC.AMPL.THRU2	muse_throughput..thru2	[%] Channel throughput compared to photodiode 2	HC		[docuSys coming]
QC.AMPL.THRU2ERR	muse_throughput..thru2err	[%] Estimated error of throughput compared to photodiode 2	HC		[docuSys coming]
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter **There might be more than one.

Trending

We monitor the throughput averaged across all the 24 chanels (IFUs) compared to the "photodiode 1" and to the "photodiode 2" (in percent). We also trend estimated error of throughput compared to "photodiode 2" (in percent). The values of the parameters do not directly correspond to absolute measure of instrument's throughput. This is a relative measurement.

Scoring&thresholds Throughput

The tight lower threshold is set empirically to detect decrease of the throughput but also, possible photodiode failures.

History

Date	event
July 2014	Throughput calibrations are taken regularly
2015-03-31	CHAN01 detector vessel exchanged, DET.CHIP.ID changed from psyche to egeria

Algorithm Throughput

Several separate amplifier images (flat-fields with special FITS headers containing pico amplifier measurements) are combined into one master image file. To compute the throughput the image is converted into a pixel table, the flux is then integrated over the given filter band, and the ratio of the expected flux (FITS header INS.AMPL2.CURR) to measured flux is taken, in the same units. The resulting ratio is the instrument efficiency (throughput).

We also monitor throughput of the instrument measured from observations of the spectrophotometric standard stars.

QC1_parameters

FITS key	QC1 database: table, name	definition	class*	HC_plot**	more docu
QC.STANDARD.THRU5000	muse_std..std_thru5000	Throughput computed at 5000 &/- 100 A	HC		[docuSys coming]
QC.STANDARD.THRU7000	muse_std..std_thru7000	Throughput computed at 7000 &/- 100 A	HC		[docuSys coming]
QC.STANDARD.THRU8000	muse_std..std_thru8000	Throughput computed at 8000 &/- 100 A	HC		[docuSys coming]
QC.STANDARD.THRU9000	muse_std..std_thru9000	Throughput computed at 9000 &/- 100 A	HC		[docuSys coming]
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter **There might be more than one.

Trending

The throughput of the instrument measured from observations of the spectrophotometric standard stars is monitored. The thoughput is estimated in different wavelength bands +/- 100 A wide centered at: 5000 A, 7000 A, 8000 A and 9000 A. The 6000 A band is not used as it is affected by the presence of Na Notch filters in the AO mode. Only data points determined from calibrations taken in the read out mode (DET.READ.CURNAME) SCI1.0 are selected.

Scoring&thresholds STD Throughput

No scoring

History

Date	event
2017-05-09	Pipeline updated, the std_thru parameters started being calculated
2017-09-05	M1 re-coated; std_throughput increased

Algorithm STD Throughput

The thoughput is estimated in different wavelength bands +/- 100 A wide centered at: 5000 A, 7000 A, 8000 A and 9000 A. The observed counts are integrated over the filter function, then multiplied with hc/lambda/area (where area is the effective VLT area) to get observed fluxes (f_obs). The reference fluxes are integrated over the filter function (fref) and then the zeropoint is computed as zp = -2.5 log10(fobs/fref). The throughput is calculated using formula 10^(-0.4 zp).