SPHERE Quality Control: ZIMPOL lamp and flat calibration

SPHERE ZIMPOL Quality Control:
flat and lamp calibration

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Trending & QC1
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trending & QC1

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QC1 database
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QC PLOTS
	CURRENT	HISTORY
IMG counts
IMG S/N
IMG rms
IMG plane_RMS
QC1 database (advanced users): browse \| plot
Click on CURRENT to see the current trending (Health Check). Click on HISTORY to see the historical evolution of the trending.

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.

top counts, rms

ZPL_FLAT_RAW1 ZIMPOL raw flat frame (one plane of the cube) in StandardImaging readmode of one CCD (here CAM1).

EVEN ODD Left: 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.
Right: 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.

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

QC1 parameters

(LOCAL means: there is no entry in the pipeline product fits header, the QC parameter is calculated by a QC script)

parameter	QC1 database: table, name in DB, name in header	procedure
	imaging mode flats, dbname=sphere_zimpol_flat_img
counts	qc_iframe_raw_med, DRS.ZERO.ODD.RAW.MED.MEDIAN	see pipeline user manul for details
S/N ratio	qc_SNR_iframe LOCAL (QC script)	The bias subtracted signal of the raw frame is stored in DRS.DOUBLE.IMAGE.IFRAME.MED.MEDIAN (or PFRAME) which is multiplied by NDIT to get the total number of counts. The sqrt of this expression is called the signal-to-noise ratio.
rms	qc_rms_iframe QC.DOUBLE.IMAGE.IFRAME.RMS	The RMS of the IFRAME product, see pipeline user manul for details
counts per plane	qc_plane_rms LOCAL (QC script)	From a QC script: 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.

	polarimetric mode flats, dbname=sphere_zimpol_flat_pol
counts	qc_rawmed_zero_odd DRS.ZERO.ODD.RAW.MED.MEDIAN	Box 1 in HC plot, see pipeline user manual for procedure
S/N ratio	qc_SNR_zero_odd LOCAL	Box 2 in HC plot, subtract 900 ADU from each raw frame plane median (to correct for bias value) but take only the zero phase rows of the fits cube, sum counts over all NDIT (=NAXIS3) planes and take the sqrt.
counts	qc_rawmed_pi_odd DRS.PI.ODD.RAW.MED.MEDIAN	Box 3 in HC plot, see pipeline user manual for procedure
S/N ratio	qc_SNR_pi_odd LOCAL	Box 4 in HC plot, subtract 900 ADU from each raw frame plane median (to correct for bias value) but take only the pi phase rows of the fits cube, sum counts over all NDIT (=NAXIS3) planes and take the sqrt.
rms	qc_rms_zero_odd QC.QUAD.IMAGE.ZERO.ODD.RMS	Box 5 in HC plot, see pipeline user manual for procedure, the rms of the product frame
counts per plane	qc_plane_med LOCAL	Box 6 in HC plot, values retrieved as in Box 2, but take the median over all plane medians.
rms	qc_rms_pi_odd QC.QUAD.IMAGE.PI.ODD.RMS	Box 7 in HC plot, see pipeline user manual for procedure, the rms of the product frame
counts per plane	qc_plane_rms LOCAL	Box 8 in HC plot, values retrieved as in Box 2, but take the rms over the sample of plane medians. This QC parameter is senistive to the following effect: Any plane of the cube deviates in the number of counts from that of the rest of the planes.

Trending

counts and rms are trended for a set of four broad band filters only. They come

for both detectors (CAM1 and CAM2)
in imaging mode for both cycles (I and P)*.
in polarimetry mode for all four cycles (phase zero odd subcycle, phase pi odd subcycle, phase pi even subcycle, phase zero even subcycle).

*: The pipeline products (V 0.18.0) of the imaging flat field recipe are wrongly labeled I (for intensity) and P (for polarimetric degree) and the QC parameter naming scheme follows this wrong naming. The first four FITS product extensions labeled IFRAME are in fact the processed signal of the odd CCD rows carrying the image signal, while the second set of four FITS extensions labeled PFRAME contain the processed signal of the even CCD rows, which contain only the unilluminated bias signal.

History

temporarily unsupported:

From 2015-09-09 to 2016-06-01 all zimpol calibrations, for which a lamp is involved (flats, modemeff calibrations, and optical distortion pinhole images) show a deficit.
The deficit is described on the SPHERE problems page. Since the number of underexposed planes varies, the pipeline cannot handle these calibrations. Furthermore the calibrations might suffer from a lower sign-to-noise ratio. As an operational consequence the processing focus only on the monitoring of the issue via the qc_plane_rms QC parameter, which measures the rms of the sample of plane medians.
The health check plots have been taken off the main page and are available here: flats imaging mode