SpaceX missed a satellite collision warning due to a software bug

This rocket carried 60 Starlink satellites to orbit in May.
This rocket carried 60 Starlink satellites to orbit in May.
Image: AP Photo/John Raoux
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In May, SpaceX launched 60 satellites that promised automatic collision avoidance. Over the weekend, Elon Musk’s space company missed a potential collision warning because buggy software did not relay an alert to a human operator.

Thankfully, no collision occurred, but the incident has inspired more debate about the lack of firm rules governing spacecraft in orbit around the earth, and how a new generation of space companies intends to exploit their absence with thousands of new internet satellites.

All satellite activities depend on cooperation: To understand where spacecraft are, their operators use space surveillance data collected by the US Air Force, as well as sharing tracking information amongst themselves. If a collision seems imminent—and in this case, the industry standard for action is about a 1-in-10,000 chance of conjunction—the operators collaborate and decide which satellite should move.

Last week, space surveillance data revealed that one of SpaceX’s 60 Starlink satellites and the European Space Agency’s Aeolus satellite might intersect. The odds of a collision occurring on Sept. 2 were about 1 in 50,000  when the two organizations first e-mailed about the problem on Aug. 28; according to SpaceX, both agreed not to take any action at that time.

However, the probability of a collision continued to increase, and by Sept. 1 it had fallen to 1 in 1,000. The ESA chose then to maneuver its spacecraft to a higher orbit to ensure that nothing went wrong with the multi-million dollar vehicles. A crash would not only damage and likely destroy both satellite, but also add new debris to orbit that might impact other spacecraft.

But SpaceX had fallen out of the conversation. According to a statement from the company, “a bug in our on-call paging system prevented the Starlink operator from seeing the follow-on correspondence on this probability increase—SpaceX is still investigating the issue and will implement corrective actions.”

“This example shows that in the absence of traffic rules and communication protocols, collision avoidance depends entirely on the pragmatism of the operators involved,” Holger Krag, the ESA’s head of space safety, said in a statement. “Today, this negotiation is done through exchanging emails—an archaic process that is no longer viable as increasing numbers of satellites in space mean more space traffic.”

Ahead of their launch in May, Musk promised his satellites would dodge collisions automatically. SpaceX insisted that its system would automatically relay warnings to its satellites, which would then rely on software to plan independent maneuvers. At the time, other operators were surprised, since dealing with a potential intersection is typically a three-way conversation between the operators and the USAF Combined Space Operations Center.

Now, while humans are apparently part of SpaceX’s control system, it’s not clear when. A SpaceX spokesperson told Quartz that its satellites are designed for fully autonomous collision avoidance, and said that so far the constellation had performed 16 such maneuvers without manual input.

The ESA is using the incident to call for more rules and protocols for space traffic management. But some of its commentary is seen as overblown in the industry; the ESA reported this as the first time it has dodged “a satellite from a large constellation,” but SpaceX’s initial fleet of satellites isn’t yet larger than those operated by established firms. The CEO of one of those companies, Iridium, publicly noted that such satellite maneuvers are routine.

However, calls for new protocols in orbit will only get louder. Greg Wyler, the CEO of OneWeb, another firm aiming to launch thousands of satellites in a communication network, has come out in favor of higher standards. “If we mess it up, if satellites start failing and they start crashing, there’s virtually no way to clean up the mess,” he said in July.