QC PLOTS
	CURRENT	HISTORY
Bias level, RON, structure, bad pixels
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.

2008-05-24: new GIRAFFE CCD "Carreras" operational (replacing "Bruce"), find documentation for the old and the new CCD here.
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

2011-01-11: description of fast read mode added

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 the image flats.

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'.

	BIAS frame, 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.
	BIAS frame, new CCD. The new CCD has cleaner cosmetics, there is no bad column. The gradients in X and Y are much smaller.

Find other detector parameters documented here:

Box 1 shows the mean BIAS level measured across the whole CCD, given in ADU.

QC1 parameters

Trending

The median bias level is plotted in box 1 of the trending plot.

History

There is a trending plot covering the full history of contamination (here). The mean bias has slowly decreased over the years.

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 parameters

Trending

Box 2 of the trending plot shows the RON of single raw BIAS frames, box 3 the RON of master bias frames.

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.

The GIRAFFE BIAS frames contain some structure which is monitored here.

QC1 parameters

Trending

Box 4 and 5 of the trending plot show the structure of the BIAS, derived from collapses of columns (structure in X direction, left) and rows (Y direction, right).

		Structure plots. The structure in X direction is derived in the master bias, collapsed along the rows (box 4). The structure in Y is obtained along the columns (box 5). The collapses are shown below.
Old CCD:	New CCD, normal read mode :	Collapsed master bias. While the master bias (both for the old and the new CCD) has virtually no structure in X direction (along the rows), it is quite structured vertically (along the columns). Old CCD: Roughly the first 1000 rows increase from a level about 4 ADU below average to the average level. The step is due to the bad columns around column 420 starting at about row 1460. New CCD, normal read mode: the increase is much smoother and has an amplitude of less than 2 ADU. There is no bad column.
	New CCD, fast read mode:	New CCD, fast read mode: the structure looks very similar, but not identical, to the normal read mode.

The number of bad pixels in GIRAFFE BIAS frames is monitored here. Note that the pipeline recipe delivers proper values only since 2008, for the new CCD.

QC1 parameters

Trending

Box 6 of the trending plot show the number of bad pixels which is usually between 0 and 200 in the new CCD.