The Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), a decommissioned NASA spacecraft used to study solar flares and coronal mass ejections, is expected to make an uncontrolled descent to Earth in the coming days, according to experts. The RHESSI satellite weighs just 600 pounds (270 kilograms), and most of its mass is expected to turn into vapour and ash during the crash. However, some parts of the spacecraft are predicted to survive the fall. The US military estimates that RHESSI will reenter Earth’s atmosphere on Wednesday around 9:30 pm EDT, plus or minus 16 hours.
While the chances of danger to humans are low, with odds of approximately 1 in 2,467, the descent of RHESSI serves as a reminder that Earth’s orbit is becoming increasingly congested and perilous. Currently, over 30,000 pieces of orbital debris are monitored by global space surveillance networks, but many additional pieces are too small to track. According to the European Space Agency, there are approximately 1 million objects that are 0.4 inches to 4 inches (1 to 10 centimetres) wide orbiting our planet at present. Additionally, there are approximately 130 million pieces between 0.04 inches (1 millimetre) and 0.4 inches, which could cause significant damage if they hit a crewed spacecraft or satellite.
In low Earth orbit, where many crafts fly, objects move at roughly 17,500 mph (28,160 kph). Collisions in space generate additional space debris, which could result in further collisions in the future. In the event of a Kessler Syndrome cascade, our ability to explore and utilize space could be seriously impaired.
RHESSI was launched to low Earth orbit via a Pegasus XL rocket in February 2002 to examine solar flares and coronal mass ejections using its single science instrument, an imaging spectrometer that recorded X-rays and gamma rays. During its mission tenure, RHESSI recorded more than 100,000 X-ray events, allowing scientists to study the energetic particles in solar flares.
When RHESSI comes crashing down, it will not be the largest piece of space debris to fall to Earth uncontrollably. In November, for example, the 23-ton (21 metric tons) core stage of a Chinese Long March 5B rocket fell back to Earth about five days after it launched the third and final module for the country’s Tiangong space station. All four Long March 5B missions to date have involved uncontrolled reentries of the massive core stage.
NASA and the Department of Defense will continue to monitor RHESSI’s reentry and update predictions. The location of where it will hit Earth was not disclosed amid uncertainty. Nonetheless, the likelihood of harm to anyone on Earth is low, and experts consider this event as a warning of the potential dangers of space debris and the need to address the growing issue of space congestion.
