Tiangong-1 is currently predicted to reenter the Earth’s atmosphere around April 1st, 2018 15:15 UTC ± 14 hours.For references, minus 14 hours is 0115 UTC, or Saturday night at 9:15PM EDT, midpoint is 5:15 PM EDT Sunday and the plus 14 hours time is Monday morning at 7:15 EDT. And, no, stating the time to the minute when the uncertainty is 14 hours doesn't make sense to me. With 28 hours of uncertainty, it should be plain to everyone that the buzz earlier in the month about the debris landing in Michigan was impossibly precise, and apparently just an attempt to gather some headlines. It won't be possible to predict where the debris lands until it's known when the orbit breaks down. I'll guess they won't know where the debris will be come down until about 30 minutes before impact.
That Aerospace Corporation webpage includes a video explaining the re-entry and breakup process of the 34 x 11' space station, commonly said to be the size of a "school bus" (as if they're all a standard size everywhere in the world). As atmospheric drag picks up, I'd expect the solar panels to rip off first, which they depict. After that, it's anybody's guess how much burns up and how much makes it to the surface, but some will. It should go without saying that with a total of 374 square feet of profile, some small amount of that which will make it through the atmosphere and that could hit anywhere on the 197 million square miles of the earth, including the ocean, anyone's chances of getting hit are infinitesimally small. The odds make hitting the Powerball look like a sure thing.
Pity about the possibility that it will miss Detroit.ReplyDelete
It would be like the Urban Renewal programs from the old days. I bet if it came down in some parts of Detroit no one could tell.Delete
Be more like "Urban REMOVAL".....ReplyDelete
The night Skylab came back I was at work drinking beer with my boss, and we were on conference call with several of his buddies who still worked for NASA. They weren't sure then until the last few orbits, as it's extremely hard to get accurate drag numbers on such a complex shape.
Is there a good website that is tracking it live?ReplyDelete
what you're looking for?
And it looks like SatView expects it to start re-entry over China, while US StratCom expects it to start a few orbits earlier off the west coast of Chile. Actual impact will, of course, be downrange from either location by roughly 1/2 hour and thousands of miles.Delete
Thanks Mark, I'll check it out.Delete
The very first link I posted, to Aerospace, updates on some interval that isn't specified, but has changed several times since I first looked it up. Instead of 1515 +/- 14 hours that it said when I wrote this, it has turned to 2030 +/ 8 hrs. Before I shutdown last night, it was something like 1915 +/- 9 hrs.Delete
Thanks SiG I didnt catch that link.Delete
"...could hit anywhere on the 197 million square miles of the earth..."
but in reality there is very little chance any of it will land outside the coverage of the 42.772 inclination - aero effects on the falling debris would be the only way for any of it to get there. And for LL, I would far rather that it hit the District of Corruption. Or wherever coproach spawn Hogg happens to be at moment of impact....
I just knew as I was pressing the button that someone would call me out on not reducing the area of the earth to that between the latitude limits. I just think that I'm within a factor of two on the odds and that error is far less than the uncertainty in their predictions.Delete
"And, no, stating the time to the minute when the uncertainty is 14 hours doesn't make sense to me."ReplyDelete
The expectation value of a statistical prediction is a precise number. The uncertainty value of 14 hours should be identified as the 1 sigma – but only if it's a normal probability distribution. It could be Rayleigh, but they don't say.
Statistical theory doesn't lie, but liars use statistical theory. Or something like that. There is no good way to predict the re-entry except at the last moment, when the path can be measured and the drag on the structure estimated by its observed deceleration.
And it ain't "re-entry" that's important anyway. Ain't nuthin' at the re-entry point that cares. It's downrange from there where it gets special. And that's even more difficult to predict than "re-entry". The footprint will undoubtedly extend over a significant area, but the boundaries are defined by mass and drag of the pieces parts as they break up and burn up. Or not...Delete
Of course, REAL bad luck would be to be onboard an airliner in the path and get hit by an unfortunate piece. I wonder if the NTSB would call that "pilot error"???
Heavens Above has it live, too.ReplyDelete
On a related subject there will be SSTV from the ISS Monday and Tuesday. A VHF Scanner and some free software (MMSSTV) is all you need.ReplyDelete
Latest forecast is 00:44 UTC +/- 4 minutes per SatView and US Stratcom. Over the South Atlantic which means the debris field ends up over Africa, the Middle East, the Stans, and possibly China.ReplyDelete
Let's hope Stratcom has it right. Ending up China would be more poetic. Although vast tracks are lightly inhabited.Delete
Important note for other readers following this. That 00:44 +/- 4 minutes is the difference between their stated predictions - one says 0040, the other 0048. They don't bound that with uncertainty limits.Delete
Aerospace Corp says 00:30 UTC ± 1.7 hours.
And at 22:11 UTC, SatView updated their estimate to 00:25 UTC, while the US Stratcom estimate from 21:09 UTC was still 00:48 UTC. Both on 2 April. The SatView debris field would be over Central Africa and the Middle East, while the old US Stratcom estimate would still be over the Middle East, the Stans, and China.Delete
I'm keeping an eye on it. We're well within the -1.7 hours that Aerospace says. It's 2350 UTC as I type.Delete
It would be cool to see it visually, but that ain't happening for the states.
Looks like "official" re-entry was 00:16 GMT. Although they claim it splashed down just off Tahiti, and orbital mechanics sez that had to be the time of impact for whatever piece landed there.ReplyDelete
I've noticed that. I can see it starting reentry over Tahiti closer to 0016, but the numbers just don't add up right now.Delete
Last night, I was trying to keep an eye on news for it, but nobody was doing anything. There were a handful of YouTube Live sessions that were just rebroadcasting the websites I was watching.