It's Kessler Season again

Who has "maybe GPS, phones, weather and military satellites all go away by next week" on their 2020 bingo card?

Leo Labs:

We are monitoring a very high risk conjunction between two large defunct objects in LEO. Multiple data points show miss distance <25m and Pc between 1% and 20%. Combined mass of both objects is ~2,800kg.

Object 1: 19826
Object 2: 36123
TCA: Oct 16 00:56UTC
Event altitude: 991km


Predicted close approach Thu/Fri night between a retired Parus navigation satellite (Kosmos-2004), launched in 1989, and the ChangZheng-4C Y4 third stage rocket launched in 2009.

Update: Another swing and a miss. Our long national nightmare is not yet over.

Previously, previously.

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16 Responses:

  1. Jeff Scott says:

    I had "Meteor strike or close call (nearer than moon)" so I was on the right track. And apparently they'll be a fly by on Nov 2. I did not have "Michigan Militia kidnaps Governor." I did score with "RGB Dies," so yay team?

  2. Nick Lamb says:

    GPS is MEO so this is like you hear there was a tiger got loose from a zoo in New York and you worry about your niece in Denver.

    Lots of the communications stuff is up in GEO, which is like you heard about that New York tiger and you worry about the people of France.

    Kessler syndrome is bad, but it's not Hollywood or the average mediocre SF novel where the author needed an excuse why nobody can go to space in the 22nd century or whatever.

    • margaret says:

      the CZ object is a rocket body, not the primary satellite itself.

      COSMOS 2004
      Perigee: 977.1 km, Apogee: 1,019.8 km

      CZ-4C R/B
      Perigee: 976.9 km, Apogee: 1,210.5 km

      it's possible the niece and the tiger are both due in the same borough at the same time.

      • Nick Lamb says:

        I think you haven't really understood anything I wrote, so I'll try taking it a bit more slowly.

        Jamie Zawinski, our host, describes this scenario as "maybe GPS, phones, weather and military satellites all go away by next week". Satellites orbit the planet in space. Space is really big. A famous dead guy once said that "You just won't believe how vastly, hugely, mind-bogglingly big it is" and that seems to be more true than I'd prefer.

        In particular even though COSMOS 2004 is a satellite, and the various GNSS (most famously GPS) systems also use satellites, and your satellite TV uses satellites these satellites aren't just "in space" vaguely near one another as might be convenient for say a Hollywood movie starring Sandra Bullock. Instead their orbits are very distant from each other.

        We give these orbits names, and what matters here is that we split off three very different groups with superficially similar names. LEO (Low Earth Orbit) is stuff that's really hurtling around the planet, relatively nearby, up to about 1 million meters away from us. COSMOS 2004 is down there. MEO (Medium Earth Orbit) is about 20 million meters away, this is where people put GNSS birds. GEO (Geo-synchronous Earth Orbit) is even further away, and this is where any satellites that "seem" like they aren't moving relative to you actually are, which includes many communication satellites.

        So even if this retired satellite and a used rocket collide "unleashing the tiger" in LEO (New York in my metaphor) a GPS satellite up in MEO is at negligible risk, like the niece in Denver. Does that make it OK to loose tigers in New York? No, seems like a bad idea. Kessler syndrome is a real thing, if I was, say, Elon Musk, I would be concerned about one of my shiny LEO space Internet birds getting struck by debris and about the general anti-LEO sentiment likely to arise if this happens. But Kessler syndrome is not magic, it won't suddenly make GPS and various other satellite systems "go away by next week" because space is really big.

        • margaret says:

          if your original point was that no collision was possible you are wrong. if it was that no kessler syndrome is likely then you pointed out the obvious quite poorly, but thanks for the mansplain.

      • Gordon says:

        I think he was trying to point out that this is all going on in LEO while most comms (with the notable exception of starlink et al) and gps is safely up in MEO and GEO out of harms way. Although trashing LEO would still be very not good.

    • Sounds like you're assuming 'What happens in LEO stays in LEO." But what if the debris from this hits something in an elliptical orbit?

      • Nick Lamb says:

        Humans are bad at statistics. But I'm pretty sure I have the right end of this one.

        538 estimates Donald J Trump has a 13% chance to actually win a fairly conducted 2020 US presidential election at time of writing. This makes him an underdog, but not to a point where it'd be actually crazy to think he might win [If you are currently arguing about Kessler syndrome with some random person on the Internet and haven't yet voted for Biden even though you're eligible to do so, this is your prompt]. If you believe in Luck, and you insist that 2020 is just the sort of year when Trump gets re-elected, I couldn't point to anything obviously wrong with that thinking.

        In contrast it's technically possible that Jo Jorgensen wins that election but 538 doesn't bother trying to come up with an estimate for how likely because it's dwarfed by the myriad unexpected surprises that throw everything off. A coup for example seems more likely like a Jorgensen win.

        Kessler syndrome makes sense because LEO is relatively small and relatively crowded, the energies are similar enough to be plausible, lots of statistically plausible scenarios result in another collision, and another, forming the cascade.

        In contrast, "what if?" scenarios for satellite debris collisions that amount to an aimed shot but with Mother Nature behind the scope obviously are "possible" but only like a Jorgensen presidency is possible. They're too unlikely to be worth estimating. The effort I expended writing this far exceeds what makes any sense in terms of the probability of such an unlikely event.

      • tfb says:

        I'm not sure how much stuff there is with orbits which are that elliptical. There must be reasons to put satellites in such orbits but I can't think of them.

        • Ru says:

          There's some military use for highly eccentric orbits... look up Molniya. You might also find some spent booster stages in them too, though I think people try to avoid that. Such orbits aren't commonly used, and the orbits used for military purposes are highly inclined so they wouldn't be very good at conveying crud out to GEO following a collision though the high relative velocities would make for an impressive bang.

        • Philip Guenther says:

          Elliptical orbits with periods that are rational fractions of the sidereal day will have ground-tracks that appear to "dwell" over consistent locations. Take a look at the wikipedia page for Tundra Orbit for example, where it's noted that Sirius Satellite Radio used such orbits from 2000-2016.

    • Ru says:

      Depends on how big the bangs end up being, and what things with highly eccentric trajectories are out there waiting to get hit. If you can produce a big enough cloud of debris then the odds of you hitting something in a more eccentric orbit go up, and that lofts debris higher (and lower) which can hit yet more stuff, etc etc. It might not all go by next week but it might be gone by this time next year, sort of thing.

      Not like an escaped tiger, so much as the outbreak of an exciting new disease...

  3. Looks like we dodged two large high-speed bullets - first post-pass radar check shows no new objects.

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