ESA experts have estimated that 1 in 1000 is likely to cause a collision between the two satellites, as reported by Forbes . This is a slim chance, but it was enough for ESA to decide to intervene.
"We informed SpaceX who responded and said they did not plan to take any action," Holger Krag, Head of Space Debris at ESA, told Forbes . SpaceX satellites should have automated collision avoidance systems, but this system is not used and it is not clear why.
Instead, ESA's Aeolus satellite triggers its ejection devices to move away from the area half an orbit before the potential collision occurs. In the future, ESA plans to automate the process of avoiding satellite collisions using AI. For the time being, however, the engineers there make the adjustments manually.
"Very rarely maneuvers are avoided to collide with active satellites," ESA tells Twitter . "Most of the ESA evasion maneuvers are the result of dead satellites or fragments of previous collisions."
For what it's worth, the ESA satellite occupied this particular space region nine months before Starlink arrived. However, there are no laws on space traffic and what regions satellites can occupy. This incident underscores the need for an organized international approach to space traffic.
This is not the first Starlink project dispute. Previously, astronomers complained that launching satellites created problems for telescopes. The solar panels of the satellites made them extra reflective and bright in the sky, though this was reduced after being properly oriented.
SpaceX also lost control of three of its Starlink satellites in the first month after launch. While these few satellites may have burned into the atmosphere, the failure rate has raised concerns about future project extensions. If SpaceX releases the planned 12,000 satellites for the Starlink project, the number of satellites lost could cause problems with space debris.