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| QC
PLOTS |
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CURRENT |
HISTORY |
| bias
level |
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| bias
rms |
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| bias
ron |
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| averages
low gain |
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| averages
high gain |
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| QC1
database (advanced users): browse
| plot
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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. |
Bias frames are usually measured daily in two read-out
modes:
- low gain, 1x1 binning, 2148x2440, used
for imaging,
- high gain, 1x1 binning, 2148x4096,
used for spectroscopy.
All QC parameters are computed in the central 1600x1800
pixels of each CCD.
QC1 parameters
| parameter |
QC1 database: table, name
|
procedure |
| median bias level |
vimos_bias, median_master |
median level of master bias product (which is the
median of five input frames) |
Trending
The bias level is trended for each quadrant and for each
read-out mode separately. There are also plots that show the average and
the standard deviation across all four quadrants as a quick overview of
the global behaviour.
History
July 2010: new detectors, bias level around 2500 ADU; the bias level varies with temperature, especially for quadrant 2
2011-02-21: bias level adjusted to 200 ADU on all quadrants
2011-05-19: UV flooding of Q2 detector, bias level increased by 20 ADU
2017-05-31: FIERA A (Q2/Q3) video board exchanged
QC1 parameters
| parameter |
QC1 database: table, name
|
procedure |
| read-out noise |
vimos_bias, ron_bias |
read-out noise (ron) is measured as the standard
deviation divided by sqrt(2) of the difference between the first two
raw frames in a bias stack |
Trending
Read-out noise is trended for each quadrant and for each
read-out mode separately. There are also plots that show the average and
the standard deviation across all four quadrants as a quick overview of
the global behaviour.
History
July 2010: new, thicker detectors, read-out noise measurement is strongly affected by cosmic ray hits; scoring disabled
QC1 parameters
| parameter |
QC1 database: table, name
|
procedure |
| rms |
vimos_bias, rms_master |
standard deviation of the master bias product; gives
information on the combined noise and structure components |
| fpn |
vimos_bias, fpn_master |
fixed-pattern noise (fpn) of master bias: mostly
an indicator of the presence of hot-columns. The computation of this
parameter is done by creating a shifted (by 10x10 pix) version M'
of the master M and calculating the RMS of the difference frame M
-M'. This is the combination of small-scale noise and white noise
(scaled by sqrt(2)). The white noise contribution is then quadratically
subtracted from the total noise. |
| structure |
vimos_bias, struc_master |
indicator of noise components with scales larger
than 10 pixels. It is an indicator for gradients but
it is strongly contaminated by the presence of hot-columns. The population
standard deviation of the master bias is computed (parameter RMS).
This is the combination of large scale structure, small scale structure,
and white noise. The white noise and the small scale structure contributions
are then quadratically subtracted. |
Trending
RMS is trended for each quadrant and for each read-out
mode separately. FPN and structure are only plotted as averages across
all four quadrants.
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