Retired Nasa satellite to crash back to Earth on Wednesday

Most of the spacecraft expected to burn up but some parts could survive re-entry into atmosphere

A view of Earth from a satellite. Photo: Nasa

A retired Nasa satellite is set to crash to Earth tomorrow after nearly 21 years of orbiting the planet.

The US space agency said it expected some parts of the spacecraft to survive a fiery re-entry into the Earth's atmosphere tomorrow.

The Reuven Ramaty High Energy Solar Spectroscopic Imager (Rhessi) spacecraft blasted off into space in 2002 to help scientists learn more about how powerful bursts of energy from the Sun are created.

"The Department of Defence predicted the 660-pound spacecraft will re-enter the atmosphere at approximately 9:30pm EDT on Wednesday, April 19 with an uncertainty of plus or minus 16 hours," Nasa said in a statement on Monday.

"Nasa expects most of the spacecraft to burn up as it travels through the atmosphere but some components are expected to survive re-entry."

The space agency said the chances of harm coming to anyone on Earth was low, at about one in 2,467.

Nasa did not reveal the trajectory of the spacecraft nor over which country or ocean the spacecraft would appear.

Rhessi was decommissioned in 2018 and has since continued to circle the Earth in a low orbit.

Defunct satellites are usually moved to the "graveyard orbit", an area about 320km farther from the farthest active satellites orbiting Earth that space agencies and companies often use for retired spacecraft.

Ones that break up over time create debris that stays in space for many years, while others head back towards the Earth and burn up in its atmosphere.

Larger parts of spacecraft, including rocket debris, can survive the re-entry.

A report by the European Space Agency last year said it had recorded more than 30,000 pieces of space debris.

"The amount of space debris in orbit continues to rise," the report said.

"While we may be more responsible with what we launch today, our current efforts are not enough.

"If we don’t significantly change the way we use launch, fly and dispose of space objects, an 'extrapolation' of our current behaviour into the future shows how the number of catastrophic in-space collisions could rise."

Debris in space can create danger for astronauts and spacecraft, and with more companies looking to launch satellite constellations, experts are worried about a crowded low-Earth orbit and a sharp rise in the levels of junk.

Manoeuvres to the International Space Station (ISS) are regularly made these days to avoid space junk.

Anti-satellite testing — the use of military-grade technology to destroy spacecraft — is also dangerous and can create thousands of pieces of debris.

In November 2021, Russia destroyed the Cosmos 1408 satellite with a missile, creating more than 1,500 pieces of orbital debris, which generated hundreds of thousands of smaller pieces.

Days later, astronauts aboard the ISS had to seek emergency shelter from the debris.

China has also been criticised over how it discards rocket remnants.

Last year, pieces of a Chinese rocket made an uncontrolled re-entry into the atmosphere and fell into the Pacific.

The events caused concern across the world, notably in Europe, where airspace over several airports in Spain was closed as a precaution.

Authorities temporarily closed the airspace over parts of Barcelona, Tarragona, Reus and Ibiza.

Last year, debris from a SpaceX Dragon spacecraft fell on a sheep farm in rural Australia.

The European Space Agency is working on technology that could be used to help other spacecraft deorbit safely.

Debris from Chinese rocket falls back to Earth - in pictures