|QC1 database (advanced users):
Click on CURRENT to see the current trending (Health Check).
Click on HISTORY to see the historical evolution of the trending.
One FLAT FIELD frame for the imaging detector
is taken every day within the VISIR daytime calibrations. It
consists of 6 raw frames, where each is illuminated with
different flux level. The changes of the flux are achieved by
illuminating detector with the "warm calibration unit"
simulating radiation of black body with different temperatures:
The FLAT FIELD frames are always obtained with the same instrument
setup: filter (INS.FILT1.NAME)=PAH1, pixel-field-of-view
(INS.PFOV)=0.127, detector integration type (DET.DIT)=0.016s the
number of detector sub-integrations (DET.NDIT)=1875 and readout
mode (DET.NCORRS.NAME)=Imager_syncABAB. The FLAT FIELD frames
are not used for calibrating science data. They are utilized
only to monitor performance of the VISIR's detectors.
- 1st frame: 20 C (keyword INS.EXTS.ACT)
- 2nd frame: 10 C
- 3rd frame: 0 C
- 4th frame: -10 C
- 5th frame: -20 C
- 6th frame: -30 C
There are also additional, technical flat fields taken every
day for both imaging and spectroscopic detector with a different
readout mode (DET.NCORRS.NAME)=Imager_nocorr_syncABAB and
Spectro_nocorr_syncABAB. However, currently they are not being
used for monitoring.
FLAT FIELD master frame of the imaging detector .
This is a pipeline product of the "visir_img_ff" recipe. It was build
by combining the 6 input raw frames. Note bright horizontal stripes
which are characteristic for the detector.
||FLAT FIELD 2nd raw frame .
This is a 2nd raw FLAT FIELD frame which corresponds to the
illumination by the black body with temperature of 10 K.
Other VISIR detector parameters that are monitored:
The following plot shows the temporal evolution of the
the number of bad pixels in the fltafield frame of the imaging detector.
For each flatfield image the median intensity is determined. Then it's
plotted against intenisty in each pixel. Ideally, all pixels should
have an equal gain, thus the plots should be straight lines with
slope of 1. However, some pixels have relative gain greater and some
smaller than 1. Those are flagged as bad pixels.
- number of bad pixels (QC1 database table visir_flat_img,
This is the number of pixels, for which the calculated relative gain falls outside the range from 1/5 to 5.