NASA solar satellite burns up over the Sahara desert

Goodbye RHESSI, thanks for all the data

NASA's defunct RHESSI solar flare satellite plummeted into Earth's atmosphere and disintegrated over the Sahara desert this week, the Department of Defense confirmed. 

Launched in February, 2002, the Reuven Ramaty High Energy Solar Spectroscopic Image (RHESSI) probe spent 16 years studying the rush of highly-energetic particles ejected from the Sun during intense outbursts.

The spacecraft was decommissioned in 2018 but continued to orbit until returning to Earth on Wednesday. The 660-pound (299kg) chunk of space junk re-entered the atmosphere on April 19 at 2021 EDT (April 20, 0021 UTC) and broke up over the Sahara Desert.

RHESSI arrived at about 21.3 degrees north latitude and 26 degrees east longitude, according to the DoD. NASA said the spacecraft mostly burnt up as it plunged through the atmosphere, although some components could have survived to be scattered somewhere over the Saharan desert. 

Named in honor of Reuven Ramaty, a longtime NASA researcher and renowned solar physics scientist, the spacecraft was the first observatory capable of performing imaging spectroscopy of energetic electrons emitted in solar flares. The images allowed scientists to trace where these particles were coming from and what energies they were being accelerated to. 

"Before RHESSI, no gamma-ray images nor high-energy X-ray images had been taken of solar flares," NASA explained.

The mission was initially planned for two years and performed better than expected – RHESSI observed the Sun longer than its 11-year solar cycle. Mission control turned off its detectors on April 12, 2018 after engineers failed to establish communications with the aging satellite and ceased all telemetry transmissions about three months later. 

Data collected by the spacecraft provided scientists with clues on how the Sun generated coronal mass ejections. These powerful bursts release energy equivalent to billions of megatons of TNT – they can frazzle satellites and disrupt communications here on Earth. 

RHESSI has recorded over 100,000 solar flares.

"Over the years, RHESSI documented the huge range in solar flare size, from tiny nanoflares to massive superflares tens of thousands of times bigger and more explosive. 

"RHESSI made discoveries not related to flares, such as improving measurements of the Sun's shape, and showing that terrestrial gamma-ray flashes – bursts of gamma rays emitted from high in Earth's atmosphere over lightning storms – are more common than previously thought," NASA concluded. ®