The European Space Agency was forced to perform a “collision avoidance maneuver” to prevent its Aeolus spacecraft from potentially smashing into one of Elon Musk’s Starlink satellites, in what is quickly becoming an all-too-common occurrence. According to SpaceX, it never received the expected alert that a collision was possible.
ESA pumped out a series of tweets yesterday describing the incident, in which the Aeolus satellite “fired its thrusters, moving it off a collision course with a @SpaceX satellite in their #Starlink constellation” on Monday morning. Launched in August 2018, the Aeolus Earth science satellite monitors the planet’s wind from space, allowing for better weather predictions and climate modeling.
Experts in the ESA’s Space Debris Team “calculated the risk of collision between these two active satellites,” determining that the safest option for Aeolus was to increase its height and have it pass over the SpaceX satellite, according to an ESA tweet. It marked the first time the ESA had to perform “a collision avoidance manoeuvre’ to protect one of its satellites from colliding with a ‘mega constellation,’” noted the space agency.
But as the ESA tweeted yesterday, as “the number of satellites in orbit increases, due to ‘mega constellations’ such as #Starlink comprising hundreds or even thousands of satellites, today’s ‘manual’ collision avoidance process will become impossible…”
An ESA graphic identified the culprit as being Starlink 44. The maneuver was done a half-Earth-orbit before Aeolus’ closest approach to the Starlink satellite. Jeff Foust from SpaceNews provides more insight into the incident:
Holger Krag, director of ESA’s Space Safety Programme Office, said in a Sept. 3 email that the agency’s conjunction assessment team noticed the potential close approach about five days in advance, using data provided by the U.S. Air Force’s 18th Space Control Squadron. “We have informed SpaceX and they acknowledged,” he said. “Over the days the collision probability exceeded the decision threshold and we started the maneuver preparation and shared our plans with SpaceX. The decision to maneuver was then made the day before.”
The odds of a collision were calculated at 1 in 1,000, which was high enough to warrant the maneuver. ESA scientists assessed the threat using data gathered by the U.S. Air Force, along with the “operators’ own knowledge of spacecraft positions,” according to SpaceNews.
In a statement emailed to Gizmodo, a SpaceX spokesperson said the Starlink team “last exchanged an email with the Aeolus operations team on August 28, when the probability of collision was only in the [1 in 50,000 range], well below the [1 in 10,000] industry standard threshold and 75 times lower than the final estimate.”
Once the U.S. Air Force’s updates showed that the probability had increased to more than 1 in 10,000, “a bug in our on-call paging system prevented the Starlink operator from seeing the follow on correspondence on this probability increase,” according to the spokesperson, who said “SpaceX is still investigating the issue and will implement corrective actions…. had the Starlink operator seen the correspondence, we would have coordinated with ESA to determine best approach with their continuing with their maneuver or our performing a maneuver.”
Yikes. This incident reveals the flimsy and primitive state of space traffic management, in which a failed communication led to ESA having to act unilaterally on the issue.
Well done, Elon Musk, incompetence does it again.