NASA says 660-pound defunct satellite to crash back to Earth - when and where it could happen

A defunct 660-pound satellite is expected to crash back to Earth and pose a potential risk of harm. According to NASA, the now-retired satellite, known as RHESSI, will make an “uncontrolled re-entry” through Earth’s atmosphere at 9.30pm EDT on Wednesday, April 19 - 2.30am BST on Thursday, April 20.

The RHESSI, short for Reuven Ramaty High Energy Solar Spectroscopic Imager, was launched by NASA in February 2002 to observe solar flares and coronal mass ejections from its low-Earth orbit.

However, due to “communications difficulties”, the satellite was decommissioned in August 2018, according to the agency’s Goddard Space Flight Center in Greenbelt Maryland. The US Department of Defense said although it is expected to crash back to Earth at this hour, there’s still an uncertainty of 16 hours in either direction.

Despite the potential risk of harm, NASA anticipates that most of the satellite will burn up as it travels through the atmosphere. However, the agency claims that “some components are expected to survive. NASA said the probability of the falling satellite causing harm is ‘low’ at about one in 2,467.

According to Space.com, the RHESSI satellite studied solar flares and coronal mass ejections using its single science instrument, an imaging spectrometer that recorded X-rays and gamma rays.

NASA officials wrote in Monday’s update: "During its mission tenure, RHESSI recorded more than 100,000 X-ray events, allowing scientists to study the energetic particles in solar flares. The imager helped researchers determine the particles’ frequency, location and movement, which helped them understand where the particles were being accelerated."

RHESSI will be far from the biggest hunk of space junk to fall to Earth uncontrolled when it comes down. Last November, for instance, the 23-ton (21 metric tons) core stage of a Chinese Long March 5B rocket came crashing back to Earth about five days after it launched the third and final module for the nation’s Tiangong space station.

There are no details on where and when exactly it could land yet as NASA and the US Department of Defense continue to monitor the situation.