A decommissioned NASA spacecraft, the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), is scheduled to reenter Earth’s atmosphere on Wednesday, with a probability of some components impacting the planet’s surface. The majority of the 300-kilogram (660-pound) vehicle is anticipated to disintegrate upon atmospheric entry at high velocity; however, certain sections are expected to endure the descent.
NASA estimates that the risk of injury to individuals on the ground is minimal, with a likelihood of approximately 1 in 2,467. RHESSI is predicted to reenter Earth’s atmosphere around 21:30 ET on Wednesday, April 19, with an uncertainty margin of ±16 hours. NASA and the Department of Defense will persistently track the spacecraft’s trajectory, refining predictions and potentially providing a landing zone as new information becomes available.
RHESSI operated from 2002 to 2018, observing solar flares and coronal mass ejections from its low-Earth orbit, which furthered the understanding of the underlying physics governing these potent energy releases. The spacecraft’s capabilities included imaging high-energy electrons responsible for a significant portion of the energy discharged in solar flares. Utilizing its imaging spectrometer, RHESSI achieved the unprecedented feat of capturing gamma-ray images and high-energy X-ray images of solar flares.
Data collected exposed the remarkable variation in flare sizes, spanning from diminutive nanoflares to colossal superflares, magnitudes greater in size. RHESSI’s contributions were essential to advancing knowledge about solar flares and their associated coronal mass ejections, events that discharge energy equivalent to billions of megatons of TNT into the solar atmosphere within minutes, potentially impacting electrical systems on Earth.
The mission also refined measurements of the Sun’s shape and revealed that terrestrial gamma-ray flashes—gamma-ray bursts emitted high in Earth’s atmosphere above certain thunderstorms—occur more frequently than initially surmised. NASA decommissioned RHESSI in 2018 due to challenges in maintaining communication with the spacecraft. After remaining in low-Earth orbit for five years, RHESSI is now approaching its incandescent demise.
