The European Space Agency confirmed that it was forced to maneuver one of its Earth science satellites in order to avoid a potential collision with a SpaceX Starlink satellite. The satellite in question, identified as Starlink 44 is one of 60 launched in May aboard a Falcon 9.
Confirmation of the maneuver performed by the Aeolus satellite was shared in a series of tweets from the ESA Operations account on September 2. “Experts in our #SpaceDebris team calculated the risk of collision between these two active satellites, determining the safest option for #Aeolus would be to increase its altitude and pass over the @SpaceX satellite,” the agency stated in one such tweet.
ESA officials did not publish details of exactly how close the two satellites would have passed. However, data from the Center for Space Standards & Innovation, which maintains the Satellite Orbital Conjunction Reports Assessing Threatening Encounters in Space (SOCRATES), indicated that the two satellites would have passed within four kilometers of one another.
Despite the relatively close approach, SOCRATES calculated the probability of a collision was less than one in one million. This small a chance of collision would not ordinarily warrant an avoidance maneuver. More accurate orbital paths from the operator may, however, have indicated something SOCRATES, which uses publicly available orbital data could not.
Yesterday’s avoidance maneuver was not the first by an ESA satellite, with the agency’s satellites routinely commanded to avoid space junk and dead satellites. The agency has, however, confirmed that yesterday’s maneuver was one of the very rare occasions it was forced to avoid an active satellite. This has brought into question whether mega constellations like the SpaceX Starlink project can be maintained safely.