Washington: Reuven Ramatti High Energy Solar Spectroscopic Imager (RHESSI), a retired NASA satellite, is expected to re-enter Earth’s atmosphere on Wednesday, nearly 21 years after its launch. The US space agency said that there is no danger to humans. Launched in 2002, RHESSI observes solar flares and coronal mass ejections from its low-Earth orbit, helping scientists understand the physics underlying how such powerful bursts of energy are created. NASA retired it in 2018 after 16 years due to communication difficulties.
The US Department of Defense, which is monitoring the satellite, expects the 660-pound spacecraft to re-enter the atmosphere on Wednesday around 9:30 a.m. EDT (7 a.m. IST), but the timing may vary.
While NASA expects most of the spacecraft to burn up as it travels through the atmosphere, some components are expected to survive re-entry.
“The risk of harm to anyone on Earth is small — about one in 2,467,” the agency said in a statement.
The spacecraft launched aboard an Orbital Sciences Corporation Pegasus XL rocket with a mission to image high-energy electrons, which carry a large portion of the energy released in solar flares.
It achieved this with its only instrument, an imaging spectrometer, which recorded X-rays and gamma rays from the Sun. Prior to RHESSI, neither gamma-ray images nor high-energy X-ray images had been taken of solar flares.
Data from RHESSI provided important clues about solar flares and their associated coronal mass ejections. These events release energy equivalent to billions of megatons of TNT into the solar atmosphere within minutes and can have effects on Earth, including disruption of electrical systems. Understanding them has proved challenging.
During its mission life, RHESSI recorded more than 100,000 X-ray events, allowing scientists to study energetic particles in solar flares.
The imager helped the researchers determine the frequency, location and speed of the particles, which helped them understand where the particles were accelerating.
Over the years, RHESSI documented a vast range in size from tiny nanoflares to large superflares, thousands of times larger and more explosive solar flares. RHESSI also made discoveries that are not related to flares, such as improving measurements of the Sun’s size, and showing that terrestrial gamma-ray flares – bursts of gamma rays emitted from high in Earth’s atmosphere on lightning storms – are more common than previously thought.