The International Space Station had to be pushed away from its orbit to avoid a potentially catastrophic collision with a satellite fragment.
The piece of space debris threatening the station, about the size of a human palm, is a product of the notorious 2009 collision between the defunct Russian satellite Kosmos-2251 and a functional telecommunication satellite owned by US company Iridium.
Hurtling through space at 28,800km/h, even a relatively small fragment could cause considerable damage to the $150bn orbital outpost.
The European Space Agency (Esa) said this was the first time the 109m-long and 73m-wide station had to be moved with such urgency after computer models calculated the piece of space debris would pass within 4km from the station – a margin too small to be relied on.
Esa’s Automated Transfer Vehicle Georges Lemaître, which has been docking at the station since August, was used to move the 450-ton structure, firing its thrusters to provide a boost of 1.8km/h. Commanded by a ground-based control team, Georges Lemaître pushed the station 1km away to increase the distance from the space junk’s projected trajectory.
It’s been the first time a vehicle from the ATV family has been used to perform a last minute avoidance manoeuvre. Out of the five ATVs Esa has built and launched since 2008, only the final two – Albert Einstein and Georges Lemaître – were designed to carry out such action.
Previously, only Russia’s Progress resupply vehicle was capable of moving the station.
Emergency manoeuvres allowing operators to adjust the space station’s orbit to avoid objects spotted less than 24 hours in advance were only approved in 2012. Before 2012, astronauts would have just prepared for evacuation and waited for the outcome of the situation.
Georges Lemaître, which delivered more than 6.6 tonnes of cargo to the ISS this August, will stay attached to the station's Zvezda module until February when it will be sent back toward the Earth packed with garbage to burn in the Earth’s atmosphere.
During its re-entry, the vehicle will demonstrate a new de-orbiting procedure designed to allow safe decommissioning of the ISS itself after the end of its operational life in the 2020s.
Esa won’t build further ATVs after Georges Lemaître but will use the technology developed over the programme’s lifetime to build systems for Nasa’s interplanetary Orion space capsule.