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article imageESA probe and SpaceX satellite avoid a 'near-collision'

By Karen Graham     Sep 4, 2019 in Technology
The European Space Agency fired the thrusters on its Aeolus satellite Monday to avoid a potential collision with a SpaceX Starlink satellite. Now it turns out SpaceX just didn't see the message that it might need to move out of the way.
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.”
However, 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 "Aeolus" satellite  shown in a digital representation  will be placed at an altitude o...
The "Aeolus" satellite, shown in a digital representation, will be placed at an altitude of 320 kilometres (200 miles) above the Earth
Handout, ESA/AFP
So, while the ESA emailed SpaceX about the collision probability increasing - SpaceX said the company missed an update from the US Air Force. "But a bug in our on-call paging system prevented the Starlink operator from seeing the follow-on correspondence on this probability increase," SpaceX said, adding that had the message been seen, it would have co-ordinated with the ESA to determine who should give way.
SpaceX says it is investigating the issue and plans to implement "corrective actions," reports CBC Canada. It is all well and good that ESA was alert to all possibilities involving the near-collision and was able to successfully perform the evasive maneuver.
"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 tweeted via its ESA Operations account.
View of the 60 Starlink satellites from the May 24  2019 launch
View of the 60 Starlink satellites from the May 24, 2019 launch
SpaceX - Starlink Mission
"The maneuver took place about 1/2 an orbit before the potential collision. Not long after the collision was expected, Aeolus called home, as usual, to send back its science data -- proving the maneuver was successful and a collision was indeed avoided."
It's getting crowded up there
The near-collision brings to light several problems and concerns that need to be addressed at the international level. One of the biggest concerns is the lack of any firm traffic rules in orbit.
"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," said Krag. The ESA is proposing an automated system to monitor and deal with collision risks.
SpaceX said it is equipping its satellites with automated and manual collision avoidance capabilities, according to the Elon Musk. The company also shares position and velocity forecasts, among other data, with the U.S. Air Force and other satellite operators. A spokesperson said SpaceX is “among the first to voluntarily share ephemeris tracking data with other satellite operators and the public at”
CNet reports that in 2018, the ESA had to perform 28 avoidance maneuvers, so this problem isn't exactly a new one. But this statement is clarified by ESA. It is “very rare to perform collision avoidance maneuvers with active satellites,” according to an ESA tweet, as the “vast majority of ESA avoidance maneuvers are the result of dead satellites or fragments from previous collisions.”
It could be said that the ESA used this near-collision event, which did, indeed, take place - to raise global awareness about the burgeoning issue of space traffic management. The space agency also used this event to point out it is preparing to streamline the collision detection process with artificial intelligence.
Automated systems, the ESA noted, “are becoming necessary to protect our space infrastructure.” This will be a step in the right direction because we certainly don't need any additional debris floating around over the planet.
More about Esa, Spacex, Aeolus satellite, Starlink 44 satellite, nearcollision
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