1. RHESSI Background Spectra Vs Time

2. Qlook_bck Spectra have 491 energy channels, 1/3 keV resolution from 3 to 100 keV, 1 keV from 100 to 300 keV. Accumulated in 20 second intervals in the 5 minute ranges before and after spacecraft day, for every orbit. No data gaps or particles or SAA allowed, front decimation is corrected for. About 5e5 spectra. Spectra are averaged in 5 degree bins of the longitude of the ascending node of the orbit, and the orbital phase. This is done for the whole mission, or a given time range. Here we used 28 day time intervals from 12-feb- 2002 until 6-mar-2007

3. 15 keV background, det 3f, full mission

4. 15 keV background, Oct-2002

5. 15 keV background, Jan-2007

6. This is the full spectrum averaged for all longitude bins, at phase=150. At 15 keV the increase is about a factor of 10.

7. Rear detector spectrum. Doesn’t show the increase

8. This is the rate at 5,15,25,55 keV as a function of time for the full mission. A bump at the start of 2003, and the increase is steady after mid 2004.

9. Other detectors? Similar patterns.

18. A steady increase in background spectra shows up in the front detectors, seems worse after 2004. Different detectors are affected differently. (Maybe look at HV?) Rear detectors show a decrease in background, most likely due to loss of detector volume.