The status of the RHESSI detectors is always changing. If you are trying to determine the best detectors to use for a particular event, please take a look at these separate-detector plots available on Browser:

  • Minute-by-minute spectrum plots (click Time-Based Quicklook, magnifier, and Per-min.det. spectra)
  • Spectrograms for each orbit (click Time-Based Quicklook, magnifier, and Spectrograms)
  • Flare peak time spectrum plots (click Flare-Based Quicklook, magnifier, and Peak det. spectra)

An explanation of how to use those plots is in the RHESSI Science Nugget 'Which detectors can I use to analyze this flare?'

For more specific guidance, please contact a RHESSI expert (e.g. Brian Dennis, Richard Schwartz, Albert Shih).

23 February - 29 April 2016 - Fifth RHESSI Anneal. After over 14 years of successful operation, RHESSI completed its fifth detector anneal. From February 23, 02:19 UTC to April 29, 03:48 UTC, the detectors were heated up to repair accumulated radiation damage and then cooled back down to operating temperatures. During that time, no science observations were made. RHESSI is again obtaining science data, but with a reduced number of operating detectors (usually 2 out of 9) in order to maintain optimal detector temperatures. See the RHESSI has resumed operations Nugget and the RHESSI 5th Anneal Nugget for more information.

26 June - 13 August 2014 - Fourth RHESSI Anneal.  During the anneal, RHESSI's germanium detectors are heated up from their operating temperature of ~115 K to ~100 deg C (373 K), held at that temperature for ten days, and then cooled back down.  The detectors degrade steadily over time due to radiation damage from charged particles, and heating up the germanium restores lost sensitivity and resolution. During the anneal, RHESSI does not collect X-ray or gamma-ray data.

After this fourth anneal, five of the nine detectors (1, 3, 6, 8, and 9) have electronically separate front and rear segments, and the other four detectors are currently operating unsegmented and have thresholds of ~20 keV.  Thus, hard X-ray (>~20 keV) observations have the nominal angular resolution (~2 arcsec) and spectral resolution (~1 keV), but soft X-ray (~3-20 keV) observations have a reduction in image quality.

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. Do not use this detector for imaging or spectroscopy below 10 keV until after the next anneal (28 August 2006 to 27 November 2007).

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