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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.
Dark frames are measured daily as part of the calibration
plan in sets of 3 frames for each DIT value. Darks with DIT = 1 and 300
sec are taken every day as health check. Darks with other DITs are only
measured when they are triggered by settings used during the night.
DARK frame. Example
frame for detector #3 with DIT = 1 sec. Detector glow is present
in the corners close to the amplifiers.
level and read-out noise
All QC1 parameters for CRIRES dark exposures are measured
on the central area with x = 256 ... 768 and y = 128 ... 384 for each
detector array separately in order to avoid contamination from the detector
||QC1 database: table, name
|median dark level
||The median level of each input raw frame is determined;
the QC parameter is the average of the three values.
|read-out noise (RON)
|The difference of the second and first (RON1) and
of the third and second (RON2) input frame is calculated. The read-out noise is calculated from the difference image as follows:
- generate 100 13x13 pixel windows
- compute the pixel standard deviation in each window
- the read-out noise is the median of these measurements multiplied with sqrt(NDIT/2).
RON2 is the more reliable determination.
||This is the standard deviation of the median levels
of the three input frames.
Dark level and read-out noise depend on the DIT. Both
parameters are trended for the daily health check settings with DIT =1
and 300 sec for each detector (chip) separately. For the read-out noise,
the ron23 value is chosen.
2010-09: ron on detectors 3 and 4 increased after intervention
2011-04-14: temperature of detectors 3 and 4 adjusted, ron and dark levels back to normal
2011-10-11: ron decreased on detectors 3 and 4 after intervention because of low detector temperatures; fixed on 2011-10-17