[HN Gopher] Eu_sst: 20% probability for large satellite collision
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Eu_sst: 20% probability for large satellite collision
Author : AlphaGeekZulu
Score : 130 points
Date : 2021-04-09 15:19 UTC (7 hours ago)
(HTM) web link (twitter.com)
(TXT) w3m dump (twitter.com)
| mikewarot wrote:
| Tangent: I went to find UTC, and they've redesigned time.gov, it
| looks great on my desktop.
|
| https://time.gov/
| salamander014 wrote:
| My personal favorite time/NTP website is
|
| https://time.is/
|
| https://time.is/UTC
| gerikson wrote:
| Love time.is. You can embed JS from them in your own webpages
| for custom clocks.
| capableweb wrote:
| time.is is pretty great! Their calendar is real handy as
| well, especially to see duration between two dates:
| https://time.is/calendar
| Black101 wrote:
| I never realized that there was two time zones in Arizona...
| meowster wrote:
| It happened about a year ago, and I think one of the developers
| commented on HN:
|
| https://news.ycombinator.com/item?id=22272966
| m463 wrote:
| date -d "2021-04-09T17:18:21 UTC"
|
| result: time in your timezone (on linux)
| swsieber wrote:
| So, in about an hour.
| SethTro wrote:
| Leolabs is tracking as well. Their data suggests a slightly lower
| but >2% chance of collision
|
| https://twitter.com/LeoLabs_Space/status/1380549507390259203
| 1-6 wrote:
| _Puts away popcorn_
| ISL wrote:
| That's somewhat more comforting, but alas, hope alone is not a
| strategy.
| joezydeco wrote:
| The Leolabs Visualizer is pretty amazing. I didn't understand
| what the red gates were on the map until I looked inward -
| they're running _their own radar sites_ in different parts of
| the world to track the objects privately. That 's cool.
|
| https://platform.leolabs.space/visualization
| AlphaGeekZulu wrote:
| The two satellites involved are:
|
| OPS 6182 (10820, 1978-042A):
| https://www.n2yo.com/satellite/?s=10820
|
| SL-8 R/B (12443, 1981-041B):
| https://www.n2yo.com/satellite/?s=12443
|
| They are on head-on course. With a probability of about 80
| percent they will miss each other. With a probability of more
| than 20 percent they will impact at a speed of more than 50000
| km/h in an altitude of 780 km.
|
| The two objects are not important (an old Russian rocket piece
| and an old US weather satellite).
|
| But upon impact, the objects will create a large cloud of debris,
| that might collide with more objects, in the worst case in a
| chain reaction.
|
| The danger is not falling debris, but that they will produce more
| damage in their orbit, maybe hitting more essential space
| equipment in the future.
|
| No need to hide in a bunker.
| theginger wrote:
| Did they miss? Both those links show them still there, but I
| suspect they are calculated not real time
| londons_explore wrote:
| They missed
| cassianoleal wrote:
| Excellent explanation, thanks very much!
| [deleted]
| moring wrote:
| Can somebody give a layman explanation why the debris would
| stay in the same orbit? I would expect a lot of energy to go
| into destroying both objects, especially in a head-on
| collision.
| brandmeyer wrote:
| It doesn't. It splatters into many related orbits.
|
| https://twitter.com/EU_SST/status/1380443036862316545/photo/.
| ..
| hn_throwaway_99 wrote:
| Conservation of momentum. All of the teeny little bits of the
| two colliding objects still have the exact same average
| momentum of the two original objects, now there are just
| hundreds of thousands of them flying off in slightly
| different directions. The movie Gravity actually gives a
| fairly good, if overly dramatized, example of what happens
| when objects collide in space.
| eqvinox wrote:
| Put quite simply - the energy _doesn 't_ go into destroying
| objects. There's only a very small amount going into heating
| things up from mechanical deformation [and a bit into
| spinning], but fundamentally, splitting something in a
| million pieces just means you have a million pieces that have
| the same total kinetic energy in orbit.
|
| However, they also _exchange_ kinetic energy & impulse with
| each other, meaning you get a mix of slower and faster
| pieces. This is what the Gabbard diagram shows:
|
| https://twitter.com/EU_SST/status/1380443036862316545
|
| Anything that is sped up in the collision (i.e. "steals"
| energy from another piece) has the same perigee (orbit low
| point) but a higher apogee (orbit high point.) The reverse
| happens to anything slowed down / stolen from. That's why the
| graph looks like open scissors.
|
| Some pieces with lower perigee will friction against earth
| atmosphere and burn up, but the ones with higher apogee
| become a serious problem...
|
| (also, for anyone who can't remember to distinguish apogee &
| perigee: think of your periphery, it's the things _close_ to
| you :D)
| ithkuil wrote:
| My mental crutch is "apotheosis" (the high point of
| something)
| JshWright wrote:
| I think of "peripheral" as being "far from the center of my
| vision".
|
| Fortunately, years of Kerbal Space Program means the
| apo/peri prefixes are pretty solidly ingrained.
| eqvinox wrote:
| Ah crap :/
|
| ...well I guess the "center of vision" is the center of
| the orbit ellipse... ;D
|
| (just trying to salvage the mnemonic aid for myself)
| _0ffh wrote:
| My mental crutch was always Apogee Software. It's more
| intuitive that someone calls their company "High Point
| Software" than "Low Point Software".
| mnw21cam wrote:
| A lot of the debris won't stay in the same orbit. It'll be
| like a mini-explosion, spraying out debris in every
| direction, but then add the existing velocity to that. So
| yes, the debris will be in another orbit. The question is,
| how much of a change occurs.
|
| In the twitter thread, there is a Gabbard diagram that shows
| a prediction of the orbits that the pieces will end up in.
| The satellites currently have a reasonably circular orbit,
| with apogee (highest point) and perigee (lowest point) about
| 800km. After the collision, the apogee is likely to be higher
| and the perigee is likely to be lower, so the orbits won't be
| circular any more.
|
| The way this happens is - if the debris piece is knocked
| directly backwards, then its apogee will be about the same,
| but its perigee will be lower. If it is knocked forwards
| (yes, that can happen), then the apogee will be raised, and
| the perigee will be about the same, and the piece could
| remain in orbit for a long time. If it is knocked up or down,
| then both the perigee will be lowered and the apogee will be
| raised. If the perigee is low enough, then the pieces will
| scrape through the upper levels of the atmosphere, and de-
| orbit eventually.
|
| It looks like the prediction is for the lowest perigee to be
| about 200km. It may take a long time for even those pieces to
| de-orbit.
| stonesweep wrote:
| Does the debris have a degrading orbit and eventually get
| pulled earthward and burn up on entry? Or is that chaff out
| there floating around forever just outside the gravitational
| pull?
| toomuchtodo wrote:
| In the case of these objects, at ~800km, the time for orbital
| decay is often measured in decades.
| londons_explore wrote:
| Try millennia...
| mnw21cam wrote:
| Some of the pieces will have a lower orbit, which might be
| low enough for them to scrape the atmosphere and bring them
| down. Some of the pieces will be placed into a _higher_ orbit
| (although the lowest point won 't be raised).
| terom wrote:
| Missed? https://twitter.com/EU_SST/status/1380601898164744199
|
| > UPDATE: #EUSST's network of sensors has only detected a single
| object or echo at passes over three radars after close approach.
| Most likely, the collision between SL-8 R/B and OPS 6182 did not
| take place. We will continue observing the objects to confirm
| this assessment.
| marshmallow_12 wrote:
| it's 2021 now. They have presumably been tracking the orbits of
| there large objects for years now. Yes this is literally rocket
| science, but this collision is only a few hours away. Why can't
| they do better then a vague 20%?
| mikewarot wrote:
| You have random pieces of objects which may have already been
| impacted, tumbling, being pushed on by the solar wind, faint
| traces of Earth's atmosphere, and being tugged by
| electromagnetic and tidal effects.
|
| These pieces are in orbit at many thousands of miles per hour,
| and have a random radar cross section, depending again, on
| whatever random impacts have already done to them, their
| orientation, composition.
|
| The radar itself to track them must pass through the
| ionosphere, which itself causes variable time delays and phase
| shifts. Smaller objects return signals just above the noise
| after correlation in the receiver, most of them are just at the
| noise floor.
|
| Observations only happen when the objects are in site of the
| tracking ground stations, which only cover a small portion of
| the sky, not including the expected collision volume.
|
| All of that is just what I could recall might effect
| predictions off the top of my head... I'm amazed they can make
| predictions with any level of certainty.
| kilotaras wrote:
| Because the difference between collision and safely pass is
| less than 0.01% on the scale they model it.
| brandmeyer wrote:
| Friction is difficult to model and is the dominant source of
| uncertainty.
| iSnow wrote:
| My guess would be because sats are not perfect spheres but -
| esp in the case of a rocket stage like here - complex objects
| which have non-trivial rotation patterns because the center of
| gravity might be off the visible center. So I doubt they model
| each and every piece of space junk out there to get a super
| detailed prediction - after all, what can you do if you know
| 95% it's going to be a hit between do dead sats vs if you know
| 80%.
|
| Radar resolution of civil orgs might also be a limit.
| Rebelgecko wrote:
| The objects are about 500 miles up in the sky, potentially
| thousands of miles from the sensors looking at them, and
| traveling at 15,000 miles per hour with respect to us. Think
| about how precise your measurements would need to be to
| accurately predict the objects' positions in 24 hours to the
| nearest foot!
|
| And that's the difficulty _with_ the simplifying (and wrong)
| assumption that that outside forces don 't alter the orbit-
| even 2021, we have a lot of room for improvement when it comes
| to predicting many of the other factors that come into play,
| like solar activity and the Earth's climate.
| junon wrote:
| You're right; do some analysis yourself and tell us your
| findings ASAP please :)
| marshmallow_12 wrote:
| very funny. My sums should take me just a couple of hours...
| iSnow wrote:
| Snarky replies aren't really helpful as an answer to a
| question - even if it was in loaded form.
| marshmallow_12 wrote:
| did they hit or miss?
| hinkley wrote:
| You're off by a day. We just passed 24 hours to minimum
| distance.
| yetihehe wrote:
| No, you are off by a day. This event happened, now we're
| waiting for confirmation.
| hinkley wrote:
| Shit, you're right. I actually checked the date on my
| computer before posting. I swear it told me it was the 8th.
| What is happening.
| spzb wrote:
| Glitch in the matrix
| spzb wrote:
| How soon after the event will we find out whether they collided?
| keithwhor wrote:
| For anybody interested, they missed:
|
| https://www.n2yo.com/?s=12443|10820
|
| (Link further in thread.)
| yetihehe wrote:
| We don't know yet. Satellites (especially defunct) don't have
| active live tracking like ships. Satellite sites show them
| based on calculated trajectories.
|
| Edit: as of 2021-04-09T20:21:00Z EUSST thinks they missed.
| https://twitter.com/EU_SST/status/1380601898164744199
| jepler wrote:
| leolabs' next anticipated contact with SL-8 R/B 12443 is at
| 21:06UTC https://platform.leolabs.space/catalog/L5136#next-
| planned-pa...
|
| next anticipated contact with OPS 6182 at 20:00UTC
| https://platform.leolabs.space/catalog/L11618#next-
| planned-p...
|
| So what's that, about 90 minutes from now assuming I've got
| the right info?
| runarberg wrote:
| Are these satellites visible by telescope, can someone in
| e.g. Ankara try to spot SL-8 R/B 12443 as it as it flies
| over there in a few seconds?
| sitkack wrote:
| Is there an automated amateur run satellite tracking
| network? Just tracking points of light at dusk/dawn is an
| easy thing and wouldn't even require pointing, imagers
| could be fixed.
| superkuh wrote:
| Here's the text without having to execute arbitrary code from
| twitter.
|
| ---
|
| Update: according to #EUSST's latest estimates using data from
| its surveillance radars, the close approach between #space
| objects SL-8 R/B & OPS 6182 expected by tomorrow will have a miss
| distance under 10m and a Scaled Probability of Collision over
| 20%! +updates to follow soon
|
| See the below plot for the conjunction plane at Time of Close
| Approach (TCA) #EUSST #spacedebris #space
|
| https://pbs.twimg.com/media/EycvaPZWQAMXjV2?format=png&name=...
|
| Update: #EUSST simulations indicate that the potential collision
| between the two #space objects would generate more than 4 million
| fragments. This plot shows the Delta-V distribution of the whole
| cloud of fragments #spacedebris
|
| https://pbs.twimg.com/media/EyhGxpjXMAE-pmM?format=jpg&name=...
|
| More than 400 of the fragments generated by the potential
| collision would be larger than 20cm. Gabbard diagram shows the
| extent of orbital regimes that these simulated fragments would
| reach. #EUSST continues monitoring the probability of collision.
| Stay tuned for more updates.
|
| https://pbs.twimg.com/media/EyhQ_InWYAI5V5a?format=jpg&name=...
|
| Latest update: according to #EUSST the close approach between
| #space objects SL-8 R/B and OPS 6182 remains stable in geometry
| and in Scaled Probability of Collision. Miss distance would be
| ~21m and Scaled PoC over 20%. This should be the last estimate
| until TCA.
|
| https://pbs.twimg.com/media/EyiBCnsXEAAgrCu?format=jpg&name=...
| m463 wrote:
| you could probably do:
|
| https://web.archive.org/web/*/<URL>
|
| like
| https://web.archive.org/*/20210409153520/https://twitter.com...
| superkuh wrote:
| >The Wayback Machine requires your browser to support
| JavaScript, please email info@archive.org if you have any
| questions about this.
| m463 wrote:
| sorry wrong url munging
|
| https://web.archive.org/*/https://twitter.com/EU_SST/status
| /...
| andrepd wrote:
| Replace `twitter.com` with `nitter.eu`:
|
| https://nitter.eu/EU_SST/status/1380120766071635968
| superkuh wrote:
| I was pretty excited when I found out about nitter. After
| some months I realized that every nitter mirror only stays up
| for a few weeks before it becomes so popular it's throttled
| most of the time (like nitter.net).
|
| Also, it's 17:41 UTC now... the events of this post should be
| occuring now. Or not occuring.
| dpifke wrote:
| It's really easy to run a private instance of your own:
| https://github.com/zedeus/nitter
|
| Mine isn't publicly accessible so never gets throttled.
| barbazoo wrote:
| > Here's the text without having to execute arbitrary code from
| twitter
|
| Ok, I'll bite, what's this about? What "arbitrary" code is
| being executed when you visit Twitter?
| est31 wrote:
| You're running Javascript. It's sandboxed, which is why I
| have it enabled by default, but often the javascript in a
| website is made to spy on you and your behaviour. It's not on
| your side but on the side of the people who made the website.
|
| Personally I'm ok when something like discord breaks as it
| contains real time updates. But twitter just displays a bunch
| of text and pictues in a non real time manner. Even video can
| be played back without any js.
| bagels wrote:
| You can put a video on a page without js, but a lot of your
| customers would have a poor experience.
| yorwba wrote:
| Apparently [?]2.24% of global users are using a browser
| that doesn't fully support HTML5 video:
| https://caniuse.com/video
| fistynuts wrote:
| That's one hell of a lot of people.
| airza wrote:
| That's not _arbitrary_ code in the security sense though.
| It 's the very narrow range of things which are permitted
| to run in a javascript sandbox (more or less "things
| javascript can do in a web browser context, minus the
| extremely small chance someone is trying to drop a JS 0day
| on you using this link")
| mindslight wrote:
| > _That 's not arbitrary code in the security sense
| though_
|
| Yes it is. It's not system level, but it is indeed
| arbitrary code - users have no lasting visibility into
| what it's doing, and little ability to control it.
|
| > _It 's the very narrow range of things which are
| permitted to run in a javascript sandbox_
|
| Browsers have had a pretty naive threat model, up until
| recent Firefox with its new resist fingerprinting
| feature. Seemingly innocuous things like reporting your
| window size are vulnerabilities that are being used to
| track you, because the groups who designed the various
| web APIs had no security mindset besides sandboxing. One
| of the chief browser makers is even an unabashed
| surveillance company! It's going to take a long time to
| close or mitigate all those holes.
| capableweb wrote:
| > That's not arbitrary code in the security sense though
|
| True, you're right.
|
| > It's the very narrow range of things which are
| permitted to run in a javascript sandbox
|
| Well, yes and no. Narrow scope in terms of what other
| programming languages offer, yes. But in terms of
| limiting the amount of information that can leak from the
| user (you and your browser), it's not that narrow. And
| since est31 is making the privacy-argument, I'm guessing
| they are referring to that.
|
| Cover Your Track by EFF showcases how much information is
| actually leaking and what Twitter et al could do with it:
| https://coveryourtracks.eff.org/
| dang wrote:
| Please omit flamebait from your comments here. You started a
| totally off-topic argument about Javascript which got upvoted
| to the top of the thread, gaining mass and choking out
| interesting discussion. Not cool.
|
| https://news.ycombinator.com/newsguidelines.html
| eqvinox wrote:
| While I agree with hiding the parent commit for the
| flamebait, that also hid my on-topic layman's explanation of
| what's happening :(
|
| [Er... commit = comment... TGIF, leaving it in for fun ;D]
| dang wrote:
| Good point. I've detached
| https://news.ycombinator.com/item?id=26752335, which was
| the return to ontopicness.
| cassianoleal wrote:
| Are you able to translate this to layman's terms?
|
| Should I find a bunker?
| nwah1 wrote:
| I assume the fear of this sort of thing is the potential for
| causing Kessler Syndrome.
| soldehierro wrote:
| No, there's not a risk of space debris.
| m12k wrote:
| You don't need to find a bunker, but there's a risk that
| we'll soon have a lot more 'space debris' in orbit. If a
| collision happens, it'll basically turn the colliding
| satellites into scattershot, leading to a higher likelyhood
| of other smaller collisions with other satellites (less
| spectacular but could still disable even more satellite). Not
| sure how likely the latter scenario is, but it could get very
| costly if it did happen.
| Buttons840 wrote:
| Do near misses (hopefully) like this happen without us knowing,
| or do we track almost everything in orbit?
| the_duke wrote:
| The current tracking infrastructure detects pieces down to
| 10cm. All of those are catalogued, get identification numbers,
| and are tracked.
|
| Active sats often do small collision avoidance maneuvers.
| bagels wrote:
| Yes, but more frequently between small anonymous debris pieces
| (due to their quantity)
| AlphaGeekZulu wrote:
| Brace, brace, brace ...
| temp0826 wrote:
| https://en.wikipedia.org/wiki/Kessler_syndrome
| civilian wrote:
| edit: nevermind
| smithza wrote:
| All of those corporations are in the business of development
| and integration of satellites as well as satellite operations
| for commercial, public, and military customers.
| mckirk wrote:
| Worst case: Our planet ends up with Kessler syndrome and nobody
| will launch a satellite for quite a while... But in the bright
| side, I'm fairly sure your stocks wouldn't be alone in tanking
| if that happened.
| artemonster wrote:
| How likely is a massive satellite collapse is to happen in
| nearest future? Are there any educated guesses/estimates?
| londons_explore wrote:
| The thing to look up is "Kessler syndrome".
|
| It appears we have already passed the threshold at some
| altitudes, so a satellite collapse will happen in the future,
| but probably not for hundreds of years.
| the0nyx wrote:
| CRISIS AVERTED
| civilian wrote:
| citation?
| polishdude20 wrote:
| Is it? Or are the current satellite view websites just showing
| predicted paths?
| gmuslera wrote:
| With a bit of luck, Sandra Bullock won't be involved in a
| satellite collision this time.
| hinkley wrote:
| "Houston, I have a bad feeling about this mission."
| yetihehe wrote:
| Anyone knows above where it could happen? I see that it's almost
| 800km above earth, but what about nearest lat/lon?
| AlphaGeekZulu wrote:
| 67.820degN
|
| 176.552degO
|
| (north-east Russia)
| undecisive wrote:
| In summary, a rocket body and an old weather satellite want to
| have a nice big hug. At high speed. Producing a cloud of 4
| million fragments. 400 of which will bigger than 20cm.
|
| Except that they'll probably miss (by about 10m). Probably.
|
| Really interesting how much of this is statistical probabilities,
| and how much we can model about this. Right down to particle
| sizes.
|
| And yet, I still have so many questions. Mostly involving the
| maths from https://what-if.xkcd.com/13/ and whether we could push
| either of them out of the way...
| bagels wrote:
| It would probably take longer than the notice you might get of
| a potential collision (5-7 days)
| scanny wrote:
| I'm curious as to how they get those sizes and quantities! Too
| they have cad models of both objects or are they just taking
| the radar returns and material and making an estimate?
| bagels wrote:
| For well known objects like these, the mass and approximate
| size is known. You can Google them to find values even. The
| positional uncertainty and lack of data about attitude lead
| to modelling the objects as spheres as not so bad a choice.
|
| One algorithm that is sometimes used:
| https://link.springer.com/article/10.1007/BF03546397
| polishdude20 wrote:
| You can watch a map of both here!
|
| https://www.n2yo.com/?s=12443|10820
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(page generated 2021-04-09 23:03 UTC)