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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 o

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%?

iSnow 6y ago
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.
junon 6y ago
You're right; do some analysis yourself and tell us your findings ASAP please :)
- marshmallow_12 6y ago
  very funny. My sums should take me just a couple of hours...
- iSnow 6y ago
  Snarky replies aren't really helpful as an answer to a question - even if it was in loaded form.
  - junon 6y ago
    It wasn't snark. This is how peer review works.
kilotaras 6y ago
Because the difference between collision and safely pass is less than 0.01% on the scale they model it.
brandmeyer 6y ago
Friction is difficult to model and is the dominant source of uncertainty.
Rebelgecko 6y ago
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.
mikewarot 6y ago
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.

iSnow 6y ago

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.

junon 6y ago

You're right; do some analysis yourself and tell us your findings ASAP please :)

marshmallow_12 6y ago
very funny. My sums should take me just a couple of hours...
iSnow 6y ago
Snarky replies aren't really helpful as an answer to a question - even if it was in loaded form.
- junon 6y ago
  It wasn't snark. This is how peer review works.

kilotaras 6y ago

Because the difference between collision and safely pass is less than 0.01% on the scale they model it.

brandmeyer 6y ago

Friction is difficult to model and is the dominant source of uncertainty.

Rebelgecko 6y ago

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.

mikewarot 6y ago

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.