Click on CURRENT to see the current trending (Health Check).
Click on HISTORY to see the historical evolution of the trending.
2008-05-24: new GIRAFFE CCD "Carreras" operational
(replaced "Bruce"). Both CCDs are identical in format and size; unless otherwise specified,
the content below applies to both CCDs.
2010-01-05: description of bad pixels added
of fast read mode added
2016-04-01: the 'slow' mode is offered in VM, calibration data are processed and QC parameters are available, but they are not trended anywhere because of their very random and rare acquisition.
A set of 5 BIAS frames is measured daily as part of the routine calibration
and health check plan. The BIAS level, the read noise and the structure are monitored.
Other CCD parameters are monitored using the darks and
Since October 2010, the fast readout mode is offered in addition to
the normal readout mode. Its trending plots are set up the same way as the ones for
normal read mode, find them under 'bias_Fast'.
old CCD. There is an upward gradient of the order of several ADU which is monitored
by the STRUCTY parameter. The bright vertical feature is a bad column.
new CCD. The new CCD has cleaner cosmetics, there is no bad column. The gradients
in X and Y are much smaller.
The read noise (RON) is measured as rms in a single raw frame
and in the master bias frame, using in both cases a small central window 100x100
pixels wide. The RON of the master bias frame is about a factor sqrt(N) lower than
the raw file RON, where N typically is 5. RON is given in electrons, calculated from
the ADU value using the nominal transformation factor (CONAD = 1/gain) 2.25
e-/ADU. (The measured CONAD values are close to that value, check out here.)
QC1 database: table, name
measures rms in a single raw frame (the first one), using
a small central window 100x100 pixels wide; clip outliers below 100 and above
same, for the master bias frame
Box 2 of the trending
plot shows the RON of single raw BIAS frames, box 3 the RON of master
RON plots. Box 2 shows the RON of
single raw BIAS frames, box 3 the RON of master bias frames, typically constructed
from 5 input raw frames.