ACIS Total Bias Plots

These plots show the average value in ADU of each node of each CCD when a bias measurement was made.

• 'Plot of Bias without Overclock Subtracted' row shows plots of averages of readout counts of the CCD without overclock subtraction.
• 'Plots of Overclock' row shows plots of overclock values of the CCD.
• 'Plots of Bias with Overclock Subtracted' row shows plots of bias (subtracted overclock) of the CCD.
  • Thirty day moving averages are plotted with a red line
  • Fifth degree polynomial fitting on the moving averages is plotted with light green.
  • The envelope of the data points computed from min and max of moving averages is plotted with blue lines. The fitting was done with 5th degree polynomials.
  • The second panel shows the standard deviations of the moving average. The fitted line is a 5th degree polynomial lines.

The bias level was calculated following.

• Get acisf*bias0.fits is obtained from a database or /dsops/ap/sdp/cache/*/acis/
• Data with timed mode exposure is selected.
• Fits files were divided into 4 quads, then an average of bias level of each quad is computed. No corrections for dead spots, columns etc were included.
  

Memo

• ACIS Bias Trend---Sudden Change of Bias Values

Last Update: 11/23/2009