Here's the text without having to execute arbitrary code from twitter.
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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
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
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.
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.
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.
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.
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")
> 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/
> 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.
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.
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.
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.
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...
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?
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.
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.
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.
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.
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.
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:
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)
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.
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?
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).
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%?
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.
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.
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.
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.
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.
We don't know yet. Satellites (especially defunct) don't have active live tracking like ships. Satellite sites show them based on calculated trajectories.
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.
> 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.
97 comments
[ 2.6 ms ] story [ 108 ms ] thread---
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=...
Should I find a bunker?
https://web.archive.org/web/*/<URL>
like https://web.archive.org/*/20210409153520/https://twitter.com...
https://web.archive.org/*/https://twitter.com/EU_SST/status/...
Ok, I'll bite, what's this about? What "arbitrary" code is being executed when you visit Twitter?
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.
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/
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.
https://nitter.eu/EU_SST/status/1380120766071635968
Also, it's 17:41 UTC now... the events of this post should be occuring now. Or not occuring.
Mine isn't publicly accessible so never gets throttled.
https://news.ycombinator.com/newsguidelines.html
[Er… commit = comment… TGIF, leaving it in for fun ;D]
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.
176.552°O
(north-east Russia)
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...
One algorithm that is sometimes used: https://link.springer.com/article/10.1007/BF03546397
https://twitter.com/LeoLabs_Space/status/1380549507390259203
https://platform.leolabs.space/visualization
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.
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)
Fortunately, years of Kerbal Space Program means the apo/peri prefixes are pretty solidly ingrained.
…well I guess the "center of vision" is the center of the orbit ellipse… ;D
(just trying to salvage the mnemonic aid for myself)
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.
https://twitter.com/EU_SST/status/1380443036862316545/photo/...
Active sats often do small collision avoidance maneuvers.
https://www.n2yo.com/?s=12443|10820
https://time.gov/
https://news.ycombinator.com/item?id=22272966
https://time.is/
https://time.is/UTC
Radar resolution of civil orgs might also be a limit.
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.
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.
https://www.n2yo.com/?s=12443|10820
(Link further in thread.)
Edit: as of 2021-04-09T20:21:00Z EUSST thinks they missed. https://twitter.com/EU_SST/status/1380601898164744199
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?
> 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.