8 ms·

Some disagreement from 18SPCS. https://twitter.com/Skitt0608/status/1316922236515848195 https://twitter.com/Skitt0608/status/1316922236515848195

• Waterluvian 6y ago
  What an awfully unprofessional tweet.
  • jagger27 6y ago
    What’s so bad about it? The thumbs up emoji or the Medium plug?
    • Waterluvian 6y ago
      They’re rather rude and the “that’s why Dad loves me more” attitude. Just my opinion.
• bewaretheirs 6y ago
  Also: "There was an extremely low risk. This is the second time this year LeoLabs went on their own to declare an emergency and spin everyone up. Our crews had to increase radar coverage and write up multiple reports to the highest leadership for a non-event. " https://forum.nasaspaceflight.com/index.php?topic=52100.msg2142997#msg2142997 https://forum.nasaspaceflight.com/index.php?topic=52100.msg2...
  • robocat 6y ago
    “Experts at The Aerospace Corporation calculated much lower odds of collision: just 1 in 23 billion as of Thursday morning, with the objects projected to miss each other by about 70 meters (230 feet).” There is some pretty fancy high precision measurements going on to be able to predict orbits of space junk that accurately.
    • jagger27 6y ago
      Isn’t a 70 metre miss still effectively “a blond one” in terms of defunct satellites? LeoLabs’ only crime here seems to be that their model or measurements were a bit too fuzzy.
      • londons_explore 6y ago
        Big constellations will regularly miss eachother by similar margins... Since you want all the satellites to orbit with the exact same period, they all end up at the same altitude, which means lots of chances for a collision.
    • zaroth 6y ago
      I agree. Hard to believe those odds are credible even 24 hours out from the event at the velocity these objects were traveling. 1 in 23 billion are fantastically long odds - roughly 8 sigma. What would the confidence intervals on direction, speed, and drag measurements have to be to put the possibility of a collision during an expected 70 meter flyby at relative velocity of 50,000 kph that far out? How exactly predictable even is drag at that altitude on space junk which probably doesn’t have attitude control? For example, I think LeoLabs 1 sigma confidence interval was +/- 18 meters, but they had calculated them crossing at 25 meters apart.
      • colechristensen 6y ago
        You basically just keep observing the orbiting object and add data to refine the orbital parameters. Orbital mechanics is very nonintuitive, there is very little drag at that altitude, and the speed doesn’t really have any influence on how precise you can be. With very few perturbations the object-in-motion-stays-in-motion becomes a powerful tool because you can use the fact that nothing changes to get crazy high precision by spreading your measurements over time.
      • dmurray 6y ago
        From your numbers, you'd need to be about twice as good as LeoLabs. A one sigma CI of +/- 9 metres and a predicted separation of 70 metres leads to almost exactly your 8 sigma event (I got 6.5 sigma, but whatever). So if you think LeoLabs' numbers were credible for an outfit with 30 people, what's hard to believe about the US military being able to track satellites twice as accurately?
• aaron695 6y ago
  Crashes that we normally care about and intuitively understand happen in one dimensional space. (roads) Two dimensions, not so much. Examples outside of shipping lanes or being close to shore (~ one dimension still) would be interesting. Three dimensions, not really heard of. Even when you hear about a "Airship tether severs Cessna wing, killing three" that's back to two dimensional space and I suspect not totally random.
  • jtwaleson 6y ago
    Well, there was the 2009 satellite collision over Siberia. The problem with space debris is that it is uncontrollable and that movement isn't dampened as it is within the atmosphere.
  • coolspot 6y ago
    Not sure how roads are one-dimensional. If that was the case, then collision always happens when two points are on the same distance from beginning of the road. But I somehow manage to make it from A to B on a highway together with other cars. Roads are two-dimensional for collision calculations. Air is three-dimensional: you can be at the same latitude and longitude, but separated by elevation.
  • MauranKilom 6y ago
    Quoting from elsethread: > Since you want all the satellites to orbit with the exact same period, they all end up at the same altitude