Quality Control and
Data Processing

HC PLOTS
photometric zeropoint in J, H and K
Strehl ratio of acquired source
QC1 database (advanced users): browse | plot

The SPHERE calibration plan includes the observations of

• IRDIS CI/DBI: photometric standard stars and astrometric standard stars
• IFS: photometric standard stars and astrometric standard stars
• ZIMPOL-IMG: photometric standard stars and astrometric standard stars
• ZIMPOL-POL: unpolarized and polarized polarimetric standard stars

IRDIS photometric standard stars are acquired once a month in classical imaging mode (CI) in four broad band filters, under photometric conditions, once with closed loop and once with open loop, but both setups without coronograph. Further setup parameters are the neutral density filters and the wavefront sensor spatial filter. Most of the observations are carried out with the following neutral density filter - broad band filter combination:

• B_J + ND_2.0
• B_H + ND_3.5
• B_Ks + ND_3.5

IRDIS photometric standard stars observation raw frame; the first of 30 planes of the raw frame cube is shown.

IRDIS photometric standard star observation (left channel) processed by the IRDIS science recipe, which performs background subtraction, flat fielding and median cube collapsing.

QC1_parameters

FITS key	QC1 database: table, name	definition	class*	HC_plot**	more docu
QC.ZPOINTCORR.LEFT	sphere_irdis_photstd..qc_zpoint1_corrND	zp without ND filter [mag]	HC		[docuSys coming]
QC.ZPOINTCORR.RIGHT	sphere_irdis_photstd..qc_zpoint2_corrND	zp without ND filter [mag]	HC		[docuSys coming]
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter **There might be more than one.

Trending

Photometric standard standard stars are acquired regularly in four broad band filters Y J, H and K in open loop and closed loop. The photometric standard star catalogue in use does not contain Y-band magnitudes. No airmass dependent extinction correction is applied. The neutral density filter correction is applied. The closed loop observations are monitored. zpoint1 is derived from the left channel and zpoint2 is the value derived from the right channel.

Scoring&thresholds IRDIS Photometric zeropoint

The values are not scored.

History

• Since 2016-01, photoemetric zeropoints have been monitored via a QC procedure. Photometric standard star frames are submitted to the irdis science CI science recipe (v0.18) with option --ird.science_dbi.save_addprod=TRUE to keep one product per channel. A master background frame and a flat field are used. For the analysis, the scisoft eclipse peak command is applied with an aperture radius of 200 pixel, and a sky aperture with 210 < r < 240 pixel and with an option to deliver the FWHM of all sources. From the list of detected sources the brightest in the central window 200 pixel <= x,y <= 600 pixel is used. The total counts are converted in instrumental magnitudes which are compared with absolute magnitudes of the corresponding star for that filter in the NACO photometric standard star catalogue. The catalogue does not contain Y-band magnitudes. No extinction correction is applied.
• Since 2017-12 the pipeline recipe (v0.28) provides photometric zeropoints and Strehl ratios.

Algorithm IRDIS Photometric zeropoint

The sky is subtracted via a numerical aperture and the counts are integrated.

QC1_parameters

FITS key	QC1 database: table, name	definition	class*	HC_plot**	more docu
QC.STREHL.LEFT	sphere_irdis_photstd..qc_strehl1	strehl ratio	HC		[docuSys coming]
QC.STREHL.RIGHT	sphere_irdis_photstd..qc_strehl2	strehl ratio	HC		[docuSys coming]
QC.STREHL.LEFT.PEAK	sphere_irdis_photstd..qc_strehl1_peak	source peak [ADU]	HC		[docuSys coming]
QC.STREHL.RIGHT.PEAK	sphere_irdis_photstd..qc_strehl2_peak	source peak [ADU]			[docuSys coming]
QC.STREHL.LEFT.FLUX	sphere_irdis_photstd..qc_strehl1_flux	source flux [ADU]	HC		[docuSys coming]
QC.STREHL.RIGHT.FLUX	sphere_irdis_photstd..qc_strehl2_flux	source flux [ADU]	HC		[docuSys coming]
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter **There might be more than one.

Trending

The Strehl ratio is derived for J, H an d K. For reasons to cross-check against counts in the non-linearity regime of the detector the peak counts are monitored.

Scoring&thresholds IRDIS Strehl ratio

The values are not scored.

History

Since 2017-12 the pipeline recipe (v0.28) provides photometric zeropoints and Strehl ratios.

Algorithm IRDIS Strehl ratio

Not documented.