To RHESSI collaborators:

RHESSI has been successfully operating in space for over 12 years, and it is once again time to rejuvenate the detectors through an "anneal" procedure. RHESSI's germanium detectors will be 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. These detectors have been previously annealed three times, most recently in 2012.

We plan to start the anneal on June 26, and the entire procedure is estimated to take six weeks. During this time period, RHESSI will be unable to make X-ray or gamma-ray observations. If you have any questions about this upcoming anneal, please feel free to contact me.

Albert Shih RHESSI Deputy Mission Scientist

————— Albert Y. Shih Solar Physics Laboratory, Code 671 NASA Goddard Space Flight Center Greenbelt, MD 20771 Office: 301-286-1843