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VIRCAM Quality Control:
Bias, Reset

CAL | HC | refs | QC
Trending & QC1
QC links:
reset level
reset parameters
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 Daily Health Check templates for technical calibrations acquire each day reset frames of the following (only) setup:
  • NCORRS=Uncorr, NDIT=1, DIT=1.001100 sec

where 1.001100 is the MINDIT, the minimum possible DIT that can be achieved with the currently configured read speed. RESET calibrations are technical calibrations, they are not used to calibrate other calibrations or science date. A raw DARK frame (the read mode is double correlated) is a result of a reset-read-read sequence, where the first read result is internally subtracted from the second read result and the reset level cancels out. A raw RESET frame (the read mode is uncorrelated) is a result of a reset-read sequence which shows the reset level. No other calibrations use DET.NCORRS=Uncorr, only the technical RESET calibrations.

top bias level

QC1 parameters

parameter QC1 database: table, name procedure

reset level

vircam_reset, qc_resetmed, qc_resetrms
- The QC.RESETMED is the median of the master reset frame (= average of 5 raw bias frames). QC.RESETRMS is the RMS over over all pixel of the master bias product.
differential parameters vircam_reset, qc_resetdiff_med, qc_resetdiff_rms - A reference reset frame is maintained and updated after detector interventions. The QC.RESETDIFFRMS parameter is the median of the reset difference frame (master minus reference). The QC.RESETDIFFRMS is the robust RMS estimate of the bias difference frame.


When the instrument is warmed up and cooled down as part of a scheduled maintenance or an unexpected longer power cut on the site, the detectors show the follwing pattern: The reset level values and the reset rms values are higher than before the warm-up and decrease slowly in an asymptodic manner to the pre-intervention value. This might take weeks or longer. The strongest effect is seen in detectors #3, #13, and #14. From the long-term trend, the following warm-up events can be identified:

  • 2017-05-03 detector controller electronics power-cycled to reduce number of string horizontal stripes events in dark frames
  • 2017-03-08 closed cycle cooler intervention
  • 2015-11-25
  • 2015-06-15
  • 2015-03-25
  • 2014-07-15
  • 2013-08-06
  • 2012-12-10