QC PLOTS
	LAST	HISTORY
median level (master)
read-out noise (raw)
read-out noise (master)
fixed pattern (raw)
structure (raw)
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.

This page refers to the two CCDs installed since March 27, 2007. Data from the previous CCD can be found here. Parameters are measured and trended for each CCD and the 2 standard CCD modes:
- high gain, 100Kp/s, binning 2x2
- low gain, 200Kp/s, binning 2x2
There are also some measurements for unbinned data (binning 1x1) and fast readout mode (low gain, 625Kp/s, binning 2x2) in the QC1 database.

QC1 parameters

• median level of master bias (QC1 database table fors1_bias_2CCD, column median_master)
  This is the median level of all pixels in the master bias.
• median level of first raw bias (QC1 database table fors1_bias_2CCD, column median_raw)
  This is the median level of all pixels in the first raw bias.

History

Until 2008-03-31 the old pipeline was used, with which the medain levels were derived as follows:

• median level of master bias (QC1 database table fors1_bias_2CCD, column median_master)
  This is the median level of the master bias measured in a 1600x400 pixel window. The window is chosen to cover in both CCDs the regions that can be exposed. The short y dimension is due to the large vignetting of Chip 2.
• median level of first raw bias (QC1 database table fors1_bias_2CCD, column median_raw)
  This is the median level of the first raw bias measured in a 1600x400 pixel window. The window is chosen to cover in both CCDs the regions that can be exposed. The short y dimension is due to the large vignetting of Chip 2.

The read-out noise is measured in the master (noise_master) and in the raw (RON_r) frames. The difference between values in raw files and master files controls the efficiency of the master creation process.

QC1 parameters

• read-out noise of raw bias (QC1 database table fors1_bias_2CCD, column RON_r )
  The difference between the first and second raw bias is computed. The standard deviation of the pixel values in the difference image, divided by √2, is taken as the read-out noise of the raw bias.
• read-out noise of master bias (QC1 database table fors1_bias_2CCD, column noise_master )
  The deviation of pixel values from the median level is determined, excluding deviations by more than 3·RON_exp to avoid deviations not due to the read-out noise. This value is then taken as the read-out noise of the master bias.

History

RON_exp depends on the number of frames and the averaging method. The pipeline used until 2008-03-31 used a simple average, whereas the new pipeline does a min-max rejection of the highest and lowest pixel. Therefore it uses 3 instead of 5 frames for the averaging and therefore the noise of the master bias is higher than with the old pipeline.

QC1 parameters

• fixed pattern of raw bias (QC1 database table fors1_bias_2CCD, column FP_r)
  The difference between the first raw bias and the second raw bias (in ADU) shifted by 10x10 pixels, is computed. This is the combination of fixed pattern and read-out noise (scaled by √2). The population standard deviation of this difference is computed and divided by √2. The read-out noise is then quadratically subtracted from the total noise and the result is taken as fixed pattern.

QC1 parameters

• structure of first raw bias (QC1 database table fors1_bias_2CCD, column struct_r)
  The population standard deviation of the pixel values of the first input raw bias is computed. This is the combination of structure, fixed pattern, and read-out noise. The read-out noise and the fixed pattern contributions are then quadratically subtracted, leaving the large scale variations.