RHESSI has been successfully operating for over 14 years, and it is once again time to rejuvenate the detectors through an 'anneal' procedure. The detectors degrade steadily over time due to radiation damage from charged particles, and heating up the germanium restores lost sensitivity and resolution. This is the fifth detector anneal (see the list of all anneal dates).

This anneal started February 23 at 02:19 UTC and is estimated to take about two months. The detectors will be heated from their operating temperature of ~130 K to ~343 K, held at that temperature for ten days, and then cooled back down. During the anneal, RHESSI can not make X-ray or gamma-ray observations. (See the RHESSI 5th Anneal Nugget for more information.)




The Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) is a NASA Small Explorer Mission, launched on February 5, 2002.

RHESSI's primary mission is to explore the basic physics of particle acceleration and explosive energy release in solar flares.  This is achieved through imaging spectroscopy in X-rays and gamma-rays with fine angular and energy resolution to reveal the locations and spectra of the accelerated electrons and ions and of the hottest plasma.

Solar flares and their associated coronal mass ejections are of great scientific interest since they are so little understood. They present severe challenges to explain how the energy equivalent of billions of megatons of TNT is released in the solar atmosphere on time scales of minutes, and how so many electrons, protons and heavier ions are accelerated to such high energies. These super-energetic solar eruptive events are the most extreme drivers of space weather and present significant dangers in space and on Earth.



What is a solar flare?
How does RHESSI work?
What are the scientific objectives?
How does RHESSI make images?
RHESSI Spectroscopy