


QC PLOTS 

CURRENT 
HISTORY 
effective illumination 


QC1 database (advanced users):
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Click on CURRENT to see the current trending (Health Check).
Click on HISTORY to see the historical evolution of the trending. 
From the beginning of operations, the ISAAC calibration plan includes the regular acquisition of illumination correction calibrations. A photometric standard star is observed 16 times on a regular grid over the field of view. Calibrations are taken once or twice a year in SW: H, J, Js, Ks and LW: H, J+Block and K. In 2007 illumination correction frames have been investigated and all OBs have been reprocessed. The pipeline generates one FITs table file containing the extracted fluxes of the photometric standard star and a FITs imaging product with a polynomial. Illumination correction calibrations can be used to retrieve more accurate photometry from imaging science frames. It is recommended to use the same flatfield for the science recipe and the illumination recipe in order to eliminate the gradients intrinsic to the twilight flat.
Within the ESO VLT dataflow and QC process illumination correction frames are used only as technical calibrations to monitor the throughput of the instrument across the FOV. Hence no twilight flat correction is applied.
As an example all SWarm Kband illumination correction products are shown:






19990403 
19990602 
20010230 
20010814 
20010912 
20011109 






20020329 
20020722 
20030407 
20030408 
20040209 
20041027 






20050411 
20051212 
20060424 
20061212 
20070424 
20070912 






20071105 
20080509 
20080916 



For each OB/AB a QC report is generated showing on the left panel measured fluxes and the grid points
of the polynomial fit. On the right panel a comparison fit is shown.
For the LWarm, an example QC report is given here:
In the LWarm there appears a local depression matching star position #8 on the chip.
The second order polynomial does not resolve the local feature, but lowers the quality of the fit
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illumination parameters 
QC1 parameters
parameter 
QC1 database: table, name 
procedure 
source acquisition parameters 
isaac_illu, qc_x1, qc_y1, qc_f1 
 The position [pixel] and the counts [ADU] of the source on the first frame
 scales with square root of signal 
polynomial coefficients 
isaac_illu, qc_illum1, qc_illumx, qc_illumy, qc_illumxx, qc_illumxy, qc_illumyy 
 polynomial coefficients that fit the 17 flux values over the field of view. 
effective illumination 
isaac_illu, qc_eff_ul, qc_eff_ur, qc_eff_ll, qc_eff_lr, qc_eff_cc 
 polynomial coefficients applied to five selected points in the FOV: the four centers a quadrants and the center of the detector, the effective illumination 
mean effective illumination 
isaac_illu, qc_corr_mean 
 the mean of the five qc_eff values 
rms of mean effective illumination 
isaac_illu, qc_corr_stdev 
 the standard deviation of the five qc_eff values 
mean flux 
isaac_illu, qc_flux_mean 
 the mean of 17 flux values, used to normalize the polynomial 
rms of mean flux 
isaac_illu, qc_flux_stdev 
 the standard deviation of the sample of 17 flux values 
Trending
In addition to the flux values, the star identification including RA, DEC are stored in the QC1 database.
