OMEGACAM: Read-out noise
| read-out noise
| read-out noise for selected CCDs
QC1 database (advanced users):
BIAS read-out noise frames are taken on a daily basis during
normal VST/OmegaCAM operations. They are usually obtained during
day-time calibration and consist of two, zero second, closed
shutter, raw bias exposures. The rms scatter of the difference
frame of these two bias exposures (divided by sqrt(2)) is the
read noise in ADU.
The pipeline creates one output frame from its bias-readnoise
recipe (omega_readnoise): a fits table containing the read-noise
values for each extension
||QC1 database: table, name
| [qc.ron calculated by QC procedure] || omegacam_readnoise..qc_ron ||detector read noise (ADU)||HC|| || [docuSys coming] |
|*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter|
**There might be more than one.
The bias read-out noise averaged over all 32
detectors (in ADU) is
plotted in box 1 and of individual CCDs in box2 of the
trending plot. Box 3 shows scores for each CCD.
Scoring&thresholds Read-out noise
The averaged read-out noise and read-out noise rms values are
tightly scored, with static thresholds following the median average of
the current period. The requirement is stability on the calibration
Algorithm Read-out noise
The read-out noise is determined from a pair of zero-second bias
exposures. The rms scatter of the difference frame of these two bias
exposures (divided by sqrt(2)) is the read noise in ADU.
2012-06-04: Following the replacement of a video board in order to
address striping present in detector ESO_CCD_82, the three detectors
surrounding this CCD (namely, 81 and 83) displayed strongly varying
read-noise levels. After about two weeks this behaviour settled down
by itself. This is evident in the health check plot monitoring the
read-out noise of these three detectors (red, blue and green points)
and the unaffected detector (75, black points) shown below.
| 2016-10 || occassional increase of the RON in CCD_69 and CCD_77|
| 2018-08-20 || CCD_75 has been failing over the last several days; after closer investigation, the faulty FIERA videoboard 77 was replaced with spare 82 (PPRS-073742); since then, the CCDs_73/74/75/76 controlled by the videoboard, show increased RON values (CCD_75 in particular).|