Officials at the European Space Agency (ESA) said the manoeuvre did not affect the operations of the Aeolus satellite, which was launched in August 2018 to measure global wind speeds and directions to improve weather forecasts.
Klaus Merz of ESA’s space debris office said the incident highlighted the need to improve coordination among satellite operators as Earth’s orbit becomes increasingly crowded despite an absence of traffic rules.
The agency said it was alerted some time ago by the US department of defence about a possible collision risk between Aeolus and Starlink 44, leading it to reach out to SpaceX.
The ESA said it “was informed that no manoeuvre was planned for the Starlink satellite before the close approach”.
Mr Merz said: “There was no indication it could not manoeuvre.”
ESA engineers lifted Aeolus into a higher orbit, a move that would have been necessary anyway at some point to counteract the pull of Earth’s gravity, meaning little additional fuel was expended.
While the risk of collision was only about one in a thousand, the ESA did not want to take any risks.
A crash could have sprayed thousands of pieces of debris across a wide area, greatly increasing the chances of further collisions between satellites and clouds of space junk, Mr Merz said.
While satellites have to dodge each other from time to time, “it is really the first time that we had to do it with one of these big (satellite) constellations”, said Mr Merz.
Starlink 44, which was launched in May, is part of a so-called mega constellation of thousands of satellites with which SpaceX plans to provide internet services around the globe.
It is unclear why SpaceX did not offer to move out of Aeolus’ way. The California-based company did not immediately respond to a request for comment.
Mr Merz said the ESA would have appreciated closer communication with SpaceX, but noted that at least its engineers knew which course Starlink 44 was on.
He added: “In the end the key information we needed was there.”