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posted by janrinok on Wednesday September 04 2019, @07:31AM   Printer-friendly

About a week ago, the 18th Space Control Squadron, US Air Force, relayed warning data to the European Space Agency.

The data indicated that there was a non-negligible collision risk between ESA's Aeolus satellite and Starlink44, an active SpaceX satellite, at 11:02 UTC on Monday, 2 September.

As days passed, the probability of collision continued to increase, and by Wednesday, August 28, ESA's Ops team decided to reach out to Starlink to discuss their options. Within a day, the Starlink team informed ESA that they had no plan to take action at that point. By Thursday evening, ESA's probability threshold for conducting an avoidance manoeuvre had been reached, and preparations were made to lift Aeolus 350 meter in orbit. By Sunday evening, chances of a collision had risen to 1 in 1000, and commands were sent to the Aeolus satellite, which triggered a total of 3 thruster burns on Monday morning, half an orbit before the potential collision. About half an hour after the collision prediction time, Aeolus contacted base, and normal measurement operations could continue.

What the SpaceX satellite was doing in ESA's Aeolus orbit is not clear.

ESA has taken the opportunity to point out that, given SpaceX plans to put up 20,000 of those things, handling monitoring and avoidance semi-manually, and by mail, is no longer practical.


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  • (Score: 3, Funny) by deimtee on Wednesday September 04 2019, @09:03AM (4 children)

    by deimtee (3272) on Wednesday September 04 2019, @09:03AM (#889446) Journal

    Collision risk was 1 in 1700
    If burning that much fuel shortened the satellite's life by more than 1/1700th then moving it was the wrong choice.

    --
    If you cough while drinking cheap red wine it really cleans out your sinuses.
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  • (Score: 4, Interesting) by pe1rxq on Wednesday September 04 2019, @09:13AM

    by pe1rxq (844) on Wednesday September 04 2019, @09:13AM (#889449) Homepage

    lifetime is the wrong measure. The amount of useful science data is more interesting for a satellite as this. The longer it is up their there will be more useful data, but the data gathered earlier in its lifetime is in general more valuable.
    So if it gets damaged before it has finished its main mission it is a big loss as it might mean all data is less useful. After the main mission has finished your way of thinking starts makin more sense.

  • (Score: 0) by Anonymous Coward on Wednesday September 04 2019, @09:18AM

    by Anonymous Coward on Wednesday September 04 2019, @09:18AM (#889451)

    Most satellite fuel goes to counteracting atmospheric drag, which takes the form of raising the satellite altitude, which is what this maneuver did. And many satellites wear out or become obsolete before they run out of fuel. So this probably doesn't have any effect on the satellite lifespan at all.

  • (Score: 4, Insightful) by Immerman on Wednesday September 04 2019, @01:53PM (1 child)

    by Immerman (3985) on Wednesday September 04 2019, @01:53PM (#889519)

    That's an extremely selfish and short-sighted perspective.

    It's not only the satellites involved in the initial collision that are at risk - there's also everything else that comes anywhere near the band between their orbits that would get filled with debris from a collision.

    • (Score: 2) by deimtee on Wednesday September 04 2019, @05:15PM

      by deimtee (3272) on Wednesday September 04 2019, @05:15PM (#889591) Journal

      Not really. It's the sort of calculation insurance assessors do. If the (cost of mitigation) is greater than (probability of event * cost of event) then you are better off taking the risk.

      They are both in low circular orbits, 320km. It's extremely unlikely for any debris from a collision to have a higher perigree than the current orbit, and without active station-keeping atmospheric drag would de-orbit most of it. But you're right, a limited Kessler Syndrome should be considered as part of (cost of event).

      --
      If you cough while drinking cheap red wine it really cleans out your sinuses.