Defunct NASA spacecraft returns to Earth after 21 years

This week, almost 21 years after it was launched, a NASA satellite that monitored solar flares and aided scientists in understanding the sun's intense blasts of energy will crash to Earth.

According to NASA, the retired Reuven Ramaty High Energy Sun Spectroscopic Imager (RHESSI) spacecraft will reenter Earth's atmosphere on Wednesday at at 9:30 p.m. ET. RHESSI was launched in 2002 and was decommissioned in 2018.

The 660-pound spacecraft is likely to burn up in its entirety as it passes through the atmosphere, although some parts should survive reentry, according to the agency. According to NASA, the likelihood that anybody on Earth would suffer harm as a result of RHESSI's return is quite low—about 1 in 2,467.

The imaging spectrometer on board the spacecraft captured X-rays and gamma rays from the sun. According to NASA, the spacecraft took pictures of high-energy electrons from its prior vantage point in low-Earth orbit, which transport a significant portion of the energy generated in solar flares.

Prior to RHESSI, no gamma-ray or high-energy X-ray photos of solar flares had been captured, and information from the spacecraft shed light on the phenomenon and its accompanying coronal mass ejections.

These solar eruptions can have an impact on Earth, including the interruption of electrical infrastructure, by releasing the energy equivalent of billions of megatons of TNT into the sun's atmosphere in a matter of minutes.

The enormous size variation of solar flares, from microscopic nanoflares to colossal superflares that were tens of thousands of times bigger and more explosive, has been extensively observed by RHESSI throughout the years.

NASA said that it will watch the satellite's fall into Earth's atmosphere jointly with the Department of Defense.