Quality Control and
Data Processing

HC PLOTS
raw flat counts imaging
signal-to-noise ratio imaging
rms of master flat imaging
illumination stability imaging
QC1 database (advanced users): browse | plot
raw flat counts polarimetry V filter
raw flat counts polarimetry N_R filter
raw flat counts polarimetry N_I filter
signal-to-noise ratio polarimetry V filter
signal-to-noise ratio polarimetry N_R filter
signal-to-noise ratio polarimetry N_I filter
rms of master flat polarimetry V filter
rms of master flat polarimetry N_R filter
rms of master flat polarimetry N_I filter
illumination stability polarimetry V filter
illumination stability polarimetry N_R filter
illumination stability polarimetry N_I filter
QC1 database (advanced users): browse | plot

ZIMPOL flat frames are taken during day time using the same readmode and broadband filter as the science observations. Narrowband filter science observations are calibrated with broadband filter flats of closest wavelength. Raw flats come as single files with one extension per CCD. Each extension is a data cube (NAXIS=3) with NDIT=NAXIS3 planes/layers. ZIMPOL product frames come as one file per CCD with several extensions each.

ZIMPOL raw flat frame (one plane of the cube) in StandardImaging readmode of one CCD (here CAM1).

	ZIMPOL raw flat frame (first raw frame extension corresponding to chip1 = Callas) from above with cuts = 5800-6000 ADU to highlight the flat level and its structure in the odd rows of the CCD containing the lamp signal.
	ZIMPOL raw flat frame from above with cuts = 1100-1200 ADU to highlight the flat level and its structure in the even rows of the CCD. The signal is composed of the bias level plus some scattered light.

	ZIMPOL flat product frame. IFRAME extension showing the master flat based on the odd rows of the raw frame for CAM1 with the illuminated.
	ZIMPOL flat product frame. PFRAME extension, showing the master flat based on the even rows of the raw frame for CAM1 carrying a bias signal.

QC1_parameters

FITS key	QC1 database: table, name	definition	class*	HC_plot**	more docu
DRS.DOUBLE.IMAGE.IFRAME.RAW.MED.MEDIAN	sphere_zimpol_iflat_img..qc_iframe_raw_med	med counts in raw image frame	HC		[docuSys coming]
DRS.ZERO.ODD.RAW.MED.MEDIAN	sphere_zimpol_iflat_pol..qc_rawmed_zero_odd	polphase zero, odd cycle	HC		[docuSys coming]
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter **There might be more than one.

Trending

The raw frame counts (not bias-subtracted ~1000 ADU) are monitored for StandardImaging readmode in three broad band filters V, N_I and N_R and both detectors for the illuminayed cycle only.
It is also monitored for SlowPolarimetry and FastPolarimetry readmode for both detectors and the zero odd cycle for the same three broad band filters.

Scoring&thresholds ZIMPOL Flat counts

The QC parameter is scored with lower thresholds of 5000 ADU and upper thresholds of 55000 ADU to flag potiential saturation at 65535 ADU.

History

Date	event
2018-06	lamp counts begin to decrease
2018-07-29T16:28	LAMP_QL1 is used instead of LAMP_QL2

Algorithm ZIMPOL Flat counts

The average counts of all zero-odd sub-planes of the raw cube frame is taken.

QC1_parameters

FITS key	QC1 database: table, name	definition	class*	HC_plot**	more docu
[derived from a QC procedure]	sphere_zimpol_iflat_img..qc_SNR_iframe	signal-to-noise ratio of image frame	HC		[docuSys coming]
[derived from a QC procedure]	sphere_zimpol_iflat_pol..qc_SNR_zero_odd	polphase zero, odd cycle	HC		[docuSys coming]
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter **There might be more than one.

Trending

The signal-to-noise ratios are monitored for StandardImaging readmode in three broad band filters V, N_I and N_R and both detectors for the illuminated cycle only.
It is also monitored for SlowPolarimetry and FastPolarimetry readmode for both detectors and the zero odd cycle for the same three broad band filters.

Scoring&thresholds ZIMPOL Flat SN ratio

The QC parameter is scored with lower thresholds of 200, corresponding to 0.5% photon noise. (For narrow band filters the minimum SN-ratio is 100 due to operational reasons)

History

2018-11: flat frames can contain DIT values smaller than the technical possible minimum DIT (10sec for SlowPol and 1.1 for StandardImg and FastPol). This was fixed in 2018-11. Most of the QC parameters from early calibrations are affected, they have not been reprocessed.

Algorithm ZIMPOL Flat SN ratio

The average counts of all zero-odd sub-planes of the raw cube frame is taken. The sqrt of NDIT times these counts is the signal-to-noise ratio

QC1_parameters

FITS key	QC1 database: table, name	definition	class*	HC_plot**	more docu
QC.DOUBLE.IMAGE.IFRAME.RMS	sphere_zimpol_iflat_img..qc_rms_iframe	rms of counts image frame	HC		[docuSys coming]
QC.QUAD.IMAGE.ZERO.ODD.RMS	sphere_zimpol_iflat_pol..qc_rms_zero_odd	polphase zero, odd cycle	HC		[docuSys coming]
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter **There might be more than one.

Trending

The master flat rms values are monitored for StandardImaging readmode in three broad band filters V, N_I and N_R and both detectors for the illuminated cycle only.
It is also monitored for SlowPolarimetry and FastPolarimetry readmode for both detectors and the zero odd cycle for the same three broad band filters.

Scoring&thresholds ZIMPOL Flat RMS

The QC parameter is scored with thresholds based on statistical arguments.

History

No Remarks.

Algorithm ZIMPOL Flat RMS

The RMS of the master flat is taken.

QC1_parameters

FITS key	QC1 database: table, name	definition	class*	HC_plot**	more docu
[derived from QC procedure]	sphere_zimpol_iflat_img..qc_plane_rms	rms of raw cube plane median	HC		[docuSys coming]
[derived from QC procedure]	sphere_zimpol_iflat_pol..qc_plane_rms	rms of raw cube plane median	HC		[docuSys coming]
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter **There might be more than one.

Trending

The readout noise is trended for both chips (CAM1, CAM2 = Callas, Bartoli) and for all three read modes.

Scoring&thresholds ZIMPOL Flat shutter

The QC parameter is scored with an upper threshold of 4 ADU.

History

Since 2015-09-09 some but not all ZIMPOL lamp flats as well as ZIMPOL modemeff calibrations and optical distortion pinhole images calibrations suffer from the following effect: The first or more planes (the first detector read outs) of the raw frame data cube suffer from having not lamp counts or considerably less counts than the remaining readouts in the data cube.

The Fig. shows the median counts of the V-band imaging flats, resolved per plane of the raw frame data cube. The first four planes are not illiminated with a bias level of ~1000 ADU. Only planes 6 to 10 are fully illuminated. Blue points are from channel 1 (CAM1, Callas) and the red points are from channel 2 (CAM2, Bartoli).

Since the number of unilluminated planes varies it is not known how the data reduction recipe behaves in this situation. Master flats and modemeff frames are only processed for reasons to monitor the behaviour via the qc_plane_rms QC parameter, but products are discarded thereafter again. The corresponding health check plots are taken off the main page and are available here (WH 2016-04-14): flats imaging mode The problem is solved in 2016-06.

Algorithm ZIMPOL Flat shutter

The median counts is retrieved for any plane of the raw frame data cube. The rms of the sample is derived. This QC parameter measures if all planes of the cube are illuminated or if some planes are affected by the shutter problem.