An old NASA satellite is about to crash into Earth

RHESSI, a former NASA space observatory, will be thrown into the Earth’s atmosphere. The crash of this retired satellite is expected to occur on the night of April 19-20, 2023, around the same time as a solar eclipse.

A NASA satellite is about to crash into the Earth’s atmosphere. On April 17, 2023, the American space agency announced that its RHESSI (Reuven Ramaty High Energy Solar Spectroscopic Imager) satellite, once intended for the observation of solar flares, would crash on our planet. The impact must take place on the night of Wednesday 19 to Thursday 20 April.

This final crash does not mark the end of RHESSI’s mission, as the satellite has already been retired for years. Its mission, which began on February 5, 2002, ended on August 16, 2018. After 16 years of activity, NASA preferred to decommission its satellite, which ended up encountering communication problems.

Does the crash of RHESSI on Earth represent a risk?

According to indications from NASA, RHESSI should enter the atmosphere around 3 a.m. (Paris time) on April 20 – with an uncertainty of more or less 16 hours, compared to this announced time. The observatory’s return of about 300 kg into the atmosphere will be closely monitored by NASA, as well as the United States Department of Defense.

According to the space agency, the satellite should be almost destroyed upon contact with the atmosphere, “but some components should survive re-entry. The risk of anyone on Earth being harmed is low — about 1 in 2,467“. There is therefore no reasonable cause for concern.

Representation of RHESSI in space. // Source: NASA

What have astronomers learned from the RHESSI satellite?

The solar observatory, positioned in low Earth orbit, bows out with a fine track record. RHESSI had been able to study a complete solar cycle (11 years) and recorded more than 100,000 X-ray events. The satellite made images of the photons emitted during solar flares. Upon learning of the satellite’s upcoming crash, scientists remembered their work based on its data.

It was an immense privilege to be part of the science team for this mission at the start of my postdoctoral career at NASA’s Goddard [Space Flight Center],” commented on Twitter Ryan Milligan, professor of astrophysics at Queen’s University. of Belfast (Ireland). “An astonishing mission, which taught us so much about solar flares, [coronal] mass ejections, particle acceleration”, also underlines astrophysicist Peter Thomas Gallagher, director of the Dunsink Observatory (Ireland), who worked on the instruments of RHESSI at its launch.

Coincidentally, the RHESSI crash could occur around the same time as an astronomical phenomenon involving the Sun, which the observatory has helped so much to understand. A solar eclipse is announced on the night of April 19 to 20. The phenomenon will be particularly visible in Australia. The moment of the RHESSI crash is predicted only 2 hours before the total eclipse ( without taking into account the margin of more or less 16 hours). “Imagine, a burning spacecraft transiting in front of the visible solar corona,” dreamed a solar physicist, Ryan French, of the National Solar Observatory (New Mexico) on Twitter.


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