17 January - 22 February 2012 - Third RHESSI Anneal.  On 22 February, RHESSI resumed collecting solar X-ray and gamma-ray  data, following the successful completion of the "anneal" procedure to rejuvenate the RHESSI detectors from the effects of radiation damage. The detectors were heated up from their operating temperature of ~100 K to ~100 deg C (373 K), held at that temperature for ten days, and then cooled back down.  The entire procedure took five weeks.  Among the result of the anneal:

  • All 9 detectors recovered energy resolution and sensitivity.
  • Detectors #2 and #4 have higher background because they have not divided into two segments.
  • Cryocooler efficiency improved.

16-March - 1 May 2010 - Second RHESSI Anneal.  As of 1 May, RHESSI is fully operational after the second anneal.  This anneal was performed somewhat ahead of schedule, triggered by an anomaly in the RHESSI power system that occurred on 16 March 2010.  The anomaly turned off all nonessential components including the cryocooler needed to keep the germanium detectors at their <100K operating temperature.  Since the detectors were already warming up, the anneal was performed, heating the detectors to 100 degrees C for ten days.  Read more about RHESSI's Anneal Adventure.

5-27 November 2007 -  First RHESSI Anneal.  The RHESSI germanium detectors were annealed starting ~07:00 UT on 5 Nov.  At ~20:00 Ut on 27 Nov, RHESSI resumed taking science data.

28 August 2006 - At 18:07:47 UT the lower-level threshold on detector G8 was raised to around 6 keV to eliminate excessive low-energy noise. After this date, do not use this detector for imaging or spectroscopy below 10 keV.

9-24 June 2006 - From 05:00 UT on 9 June through 22:00 UT on 24 June, RHESSI was pointing off the Sun for Crab Nebula observations. This includes the re-pointing periods on either end. If you are interested in analyzing Crab or solar data in this interval, please contact the instrument team.

RHESSI Major Events, 2002 - 2007

Table of Anneal and Offpoint Times