After 24 years of diligently studying Earth’s magnetic field, a satellite will nearly burn up during a “targeted” re-entry into the atmosphere over the Pacific Ocean on Sunday, a first for the European Space Agency as it strives to reduce space debris.
Since its launch in 2000, the SALSA satellite has helped shed light on the magnetosphere, a powerful magnetic shield that protects Earth from solar winds — and without which the planet would be unfit for life.
According to ESA, SALSA’s homecoming will mark the first “targeted” reentry for a satellite, meaning it will return to Earth at a specific time and place but will not be controlled while reentering the atmosphere.
Teams on the ground have already performed several steps with the 550-kilogram (1,200-pound) satellite to ensure it burns up over a remote and uninhabited region of the South Pacific off the coast of Chile.
This unique re-entry is made possible thanks to SALSA’s unusual elliptical orbit. During one orbit around the planet, which takes two and a half days, the satellite strays as far as 130,000 kilometers (80,000 miles), coming as close as just a few hundred kilometers.
Bruno Sousa, head of ESA’s Inner Solar System Mission Operations Unit, said it was significant that SALSA came within about 110 kilometres during its final two orbits.
“Immediately after this, in the next orbit, it will descend to an altitude of 80 kilometres, which is the region within the atmosphere in space where it is most likely to be completely captured and burn up,” he said at a press conference.
When a satellite begins to enter the atmosphere, about 100 kilometres above sea level, the intense friction with atmospheric particles – and the heat generated by it – begins to disintegrate them.
But some pieces could still find their way back to Earth.
Fear of ‘cascading’ garbage into space
ESA hopes to be able to detect where SALSA, which is about the size of a small car, re-enters within a few hundred metres of the atmosphere.
Because the satellite is so old, it doesn’t have any new technology — such as recording devices — making this part difficult to detect.
An aircraft will fly at an altitude of 10 kilometres to watch the satellite burn up – and keep an eye on its falling debris, which is expected to be just 10 percent of its original mass.
SALSA is one of four satellites that are part of ESA’s Cluster mission, which is now coming to an end. The other three satellites are set to meet the same fate in 2025 and 2026.
ESA hopes these re-entries will help determine what kinds of materials don’t burn up in the atmosphere, so that “in the future we can build satellites that can completely vaporize through this process,” Sousa said.
Scientists are warning about space debris, the debris left behind by the huge number of dead satellites and other missions that continue to orbit our planet.
Last year, ESA signed a “zero debris” charter for its missions through 2030.
According to Benjamin Bastida Virgili, ESA’s space debris systems engineer, there are two main threats from space debris.
“For one thing, in orbit, you run the risk that your operational satellite could collide with a piece of space debris, and that would cause a cascading impact and generate more debris, posing a threat to other missions,” he said.
The second is when old debris re-enters the atmosphere, which happens almost daily, when pieces of dead satellites or rocket parts fall back to Earth.
Bastida Virgili stressed that designing satellites that burn up completely in the atmosphere would mean “there would be no risk to the population.”
But there’s no need to worry. According to the ESA, the chance of a piece of space debris hurting someone on the ground is less than one in a hundred billion.
This is 65,000 times less likely than being struck by lightning.
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