An uncontrolled satellite will plunge through Earth’s atmosphere on Wednesday after almost 30 years in orbit.
The pioneering European satellite, known as ERS-2, is expected to break up into pieces on re-entry, the majority of which will burn up. The satellite will have a “natural” re-entry, tumbling through the atmosphere, meaning that the precise timing and location are difficult to predict.
In its most recent forecast, the European Space Agency predicted the satellite would re-enter the Earth’s atmosphere at 3.49pm on Wednesday. At this point, the satellite is expected to be over the Pacific Ocean, but an uncertainty window of more than three hours means it could be at a different point in its orbit when it starts to burn up.
When it was launched in 1995, ERS-2 “was the most sophisticated Earth-observation spacecraft ever developed and launched by Europe”, according to the ESA, and revolutionised our understanding of the climate crisis.
“It provided us with new insights on our planet, the chemistry of our atmosphere, the behaviour of our oceans, and the effects of humankind’s activity on our environment,” said Mirko Albani, the head of the ESA’s heritage space programme.
The satellite was retired in 2011 and the ESA decided to “deorbit” it to reduce the chance of a collision with another probe.
Photos of the satellite plummeting towards the atmosphere were released by the ESA on Monday. The images were taken between 14 January and 3 February, when ERS-2 was still at an altitude of more than 300km (186 miles).
It has been falling by more than 10km (6 miles) a day, with the speed of its descent increasing rapidly. When it reaches around 80km, it will start to break and then burn up. The exact timing is uncertain due to unpredictable atmospheric conditions, which can increase or decrease drag on the satellite. It is also not known which direction the tumbling satellite is facing, which also influences its trajectory.
The vast majority of the satellite will burn up, and any pieces that survive will be spread out somewhat randomly over a ground track on average hundreds of kilometres long and tens of kilometres wide.
“The risks associated with satellite re-entries are very low,” the ESA said.
“It’s worth highlighting that none of the elements that might re-enter the atmosphere are radioactive or toxic,” said Albani.
Dr James Blake, from the Centre for Space Domain Awareness at the University of Warwick, said: “There are now thousands of active and defunct satellites orbiting the Earth and ERS-2 is the latest to undertake the return leg of its journey as it re-enters the Earth’s atmosphere.
“This is a fate that awaits uncontrolled satellites and debris that can no longer counteract the drag forces exerted by the Earth’s atmosphere – indeed, operators are encouraged to speed up the re-entry of their defunct satellites to keep space clear for future missions.”
