To RHESSI collaborators:

As we prepare for RHESSI to enter its 11th year of operation, it is once again time to rejuvenate the detectors through an "anneal" procedure. RHESSI's germanium detectors degrade steadily over time due to radiation damage from charged particles, and heating up the germanium restores lost sensitivity and resolution. Starting on January 17 (UT), the detectors will be 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 is anticipated to take about a month. During this time period, RHESSI will be unable to make X-ray and 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