SPHERE IRDIS Quality Control:
standard stars

QC PLOTS
	CURRENT	HISTORY
photometric zeropoint
Strehl ratio
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.

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

Since 2017-12 the pipeline (v0.28) supports IRDIS CI photometric standard stars only.

IRDIS photometric standard stars are acquired once a month in classical imaging mode (CI) in four broad band filters, under photometric conditions, with closed loop and without coronograph. Further setup parameters are the neutral density filter, the AO loop status 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

Description of the QC script in use since 2016-01:

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.

	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

parameter	QC1 database: table, name	procedure
photometric zeropoint	sphere_irdis_photstd, qc_ZP_R, qc_ZP_L	The QC script applies the scisoft eclipse peak command to the result of the science recipe.
source position	sphere_irdis_photstd, qc_xpos_L, qc_yps_L, qc_xpos_R, qc_ypos_R	QC script: secondary QC parameter, the position of the identified star on the detector
source properties	sphere_irdis_photstd, qc_peak_L/R, qc_fwhm_L/R, qc_counts_L/R	QC script: secondary QC parameter, peak counts, full width at half maximum and total counts of the source. L=Left channel, R=Right channel
photometric zeropoint	sphere_irdis_photstd, qc_zpoint1, qc_zpoint2, qc_zpoint1_corrND, qc_zpoint2_corrND	Since 2017-12: v0.28 pipeline recipe: photometric zeropoint for the left (index 1) and the right (index 2) IRDIS channel. corrND means the zeropoint has been corrected for the dimming by the neutral density filter
Strehl ratio	sphere_irdis_photstd, qc_strehl1, qc_strehl2	Since 2017-12: v0.28 pipeline recipe: Strehl ratio of the source (1=left, 2=right)
source position	sphere_irdis_photstd, qc_strehl1/2_posx/y	Since 2017-12: v0.28 pipeline recipe: secondary QC parameter, the position of the identified star on the detector
source properties	sphere_irdis_photstd, qc_strehl1/2_flux, qc_strehl1/2_peak	Since 2017-12: v0.28 pipeline recipe: secondary QC parameter, the integrated flux and the peak counts

parameter	QC1 database: table, name	procedure
photometric zeropoint	sphere_irdis_photstd, qc_ZP_R, qc_ZP_L	The QC script applies the scisoft eclipse peak command to the result of the science recipe.

Trending

The IRDIS photometric zeropoints are trended for three broad band filters (B_J, B_H and B_Ks) and both channels (left and right).

History

• 2015-04: start of operations, no pipeline support, no QC support
• 2016-04: QC script implemented that derived the position of the star, the peak the flux and the photometric zeropoint
• 2017-12: start of pipeline support (v0.28), Strehl ratio and neutral density filter corrected photometric zeropoints are provided