XRT HOWTO --- Monitor and Report on CCD Spot Creation

N.Narukage & M.Weber; 2008-Aug-15
Edited P. Grigis; 2010-Nov-09


This is an important point: The J-side (especially Shimojo-san and Narukage-san) currently have responsibility for officially monitoring and reporting the spot status after each bakeout. This HOWTO is provided for the following reasons:


CCD bakeouts are performed every 3 to 4 weeks to mitigate the accumulation of the contamination layer. There is a concern about the formation of spots on the CCD, so we have a monitoring policy. A set of "quadrant" images are taken immediately after every bakeout, and this data is used to produce a spot map. The new spot map is compared against the previous map to determine if any new spots are formed. There is some imprecision in this method, so there is a small, symmetric distribution of pixels that show the apparent addition and subtraction of spots. This analysis is quantified and distributed to the "xrt_co" email list in a report. It is usually reviewed and discussed at the subsequent XRT-CO weekly telecon.

This HOWTO explains how to run the spot analysis software so that you can generate the report. You can use this example of a report as your template.


  1. Determine the start (starttm) and stop time (stoptm) around the quadrant data.

  2. Login to xrtco@xrtco.Note: you need to have X-display connection enabled for the IDL program to work. Login to xrtco with the "ssh -Y" option.

  3. cd ~xrtco/lib/narukage/spot_check

  4. Edit the quadrant.txt file.

  5. Start sswidl.

  6. IDL> xrt_spot_check, bakeoutID, /outf [, ec_index=nn]

    What will happen:

  7. Assess whether new spots have been formed. If the percentages of white and black pixels in the difference image are symmetric and small, then you may conclude that no new spots have formed.

  8. Prepare the Spot Check Report.

  9. Send the Report file to the "xrt_co" email list. Include a summary statement of your assessment whether new spots have been formed.

  10. Be prepared to discuss this result on email and at the next XRT Weekly telecon.