Tiangong-1 Re-entry

[ProtoJeb21]

Impact is expected to be at about 8:30 pm EST, give or take 1.7 hours (so somewhere between 6:48 pm and 10:12 pm EST). If it enters over New England, I should be seeing it VERY soon.

[cubinator]

5 minutes ago, ProtoJeb21 said:

Impact is expected to be at about 8:30 pm EST, give or take 1.7 hours (so somewhere between 6:48 pm and 10:12 pm EST). If it enters over New England, I should be seeing it VERY soon.

Which New England in the southern hemisphere are you in? It will never pass over North America again unless it makes it all the way through the night.

[cubinator]

From the telemetry it looks like it's got about one orbit left. Take one last look if you're in the right part of the world!

[Ultimate Steve]

I would have been able to see it this morning if I had gotten up early enough (and it wasn't cloudy).

If anyone here is in South America, look up in about 80 minutes.

[Brotoro]

I hope somebody gets photos or video.

[cubinator]

Satflare is overloaded right now  

Hard to say what's happening/happened

[Confused Scientist]

Satflare is back up. Tiangong-1 is currently 133.5 km high and passing over the Ivory Coast.

[Confused Scientist]

EDIT: CNN CONFIRMS TIANGONG-1 DOWN OVER SOUTH PACIFIC

https://www.cnn.com/2018/04/01/asia/tiangong-1-china-space-lab-falls-intl/index.html?adkey=bn

 

My work here is done. But first, Wikipedia has already documented the reentry. (Check the grey sidebar.) https://en.wikipedia.org/wiki/Tiangong-1#Re-entry

Edited April 2, 2018 by Confused Scientist

[MaxwellsDemon]

Aerospace.org was showing it going down some (considerable) distance off the Chilean coast.  Nobody disturbed but some fish, presumably.

[DAL59]

1 minute ago, MaxwellsDemon said:

Aerospace.org was showing it going down some (considerable) distance off the Chilean coast.  Nobody disturbed but some fish, presumably.

So much for ultimate russian roulette.

[PakledHostage]

11 hours ago, LordFerret said:

And then there's all those other cycles. We know nothing. We just think we do.

So it came down within 3 minutes of the predicted time. Maybe we do know a thing or two about space weather?...

[GoSlash27]

My livefeed must be way behind the times. I've got it off the coast of Papua New Guinea. 139.3 km, still doing orbital velocity by my numbers

Edited April 2, 2018 by GoSlash27

[tater]

The predicted time has been narrowing each time they run the data (as one would expect).

It's like my nav system in the car. It starts out saying it might take 73 minutes to get to X in Santa Fe. As it realizes that I am exceeding posted speed limits, the ETA changes, get stuck in construction, then the ETA starts slipping again, and so forth. By the time I am a few minutes away, it has corrected so that I'm... a few minutes away. My total travel time might be substantially different than the 73 minutes it claimed in my driveway, even though the last estimate was accurate within 30 seconds.

[Confused Scientist]

More CNN: https://www.cnn.com/2018/04/01/asia/tiangong-1-china-space-lab-falls-intl/index.html

[Wrench Head]

Here is a question. How could they not have a Idea of the location, but if it was an asteroid they could track its POI? At least they say they can.

[artwhaley]

12 minutes ago, Wrench Head said:

Here is a question. How could they not have a Idea of the location, but if it was an asteroid they could track its POI? At least they say they can.

 

An asteroid is on a simple ballistic trajectory.   It's easy to do the math on how long that's going to take.   This orbit was ALMOST reentering for days...  just barely being degraded by a tiny bit constantly.  In addition, the atmosphere 'swells and shrinks' depending on the sun's activity...  this difference in the density of  the upper atmosphere makes almost no difference when an asteroid barrels through it in a few seconds... but when a space station stays in that zone for days...   the small differences add up to large changes in the amount of drag applied.  And if you don't know exactly WHEN it will finally bring it down, you have no idea where!

For an in game demonstration...  compare deorbiting by setting your periapsis to the ground versus deorbiting by setting your periapsis to 68Km.   In that second example...  how many orbits will it take to come down?   Some.  Quite a few.   Every time it gets lower and slower I can give you a better guess.   That's what this was like.  But with the addition of space weather.

Edited April 2, 2018 by artwhaley

[PakledHostage]

49 minutes ago, tater said:

[snip]

Thanks for clearing that up...

The criticism that "we know nothing" was made this morning, presumably in response to this morning's re-entry predictions, so pointing out that the re-entry occurred within 3 minutes of this morning's predicted time is also valid.

Edited April 2, 2018 by PakledHostage

[Wrench Head]

@ artwhaley Yes ty for the reply That made me rethink and I see now the issues.

[YNM]

Reentry of a very-low orbiting objects are harder to predict, because the atmosphere is a very tenuous yet continuous layer up there. We don't have good models of it (nor it's feasible to have one - you'd need constant monitoring everywhere). For objects from deep space however, it's as good as the discontinuous models used in KSP planets.

[LordFerret]

13 hours ago, PakledHostage said:

Please take your climate change denial elsewhere...

Why should I? What makes your belief / opinion any more valid? No room for skepticism? I wasn't aware it was 'settled science'. And since when is it ok for you to make personal attacks on me in this light?

 

And as far as the reentry goes, up until the last verified moments all manner of speculation abound.

[YNM]

1 minute ago, LordFerret said:

Why should I ?

The forum says so, indirectly. Unless the mods are a bit lax.

[DerekL1963]

3 hours ago, PakledHostage said:

The criticism that "we know nothing" was made this morning, presumably in response to this morning's re-entry predictions, so pointing out that the re-entry occurred within 3 minutes of this morning's predicted time is also valid.

Which predicted re-entry time?  I saw at least three...  The ESA prediction, the Aerospace Corporation prediction, and the STRATCOM's prediction.  And whose morning?  The three never did entirely converge, though they got close in the last few hours.
 

4 hours ago, PakledHostage said:

Maybe we do know a thing or two about space weather?...

As recently as a month ago it was predicted to come down sometime during a window as much as a week and a half long.  By the time they could start narrowing it down to a day, it started sliding gradually to the right as space weather was actually a little calmer than predicted.  By the time they could narrow it down to an hour plus or minus a couple of hours (I.E. within the last twenty four hours) it was low enough that space weather was no longer particularly relevant.

So no, that it re-entered within 3 minutes of the center of a predicted error window says nothing about our knowledge of space weather.

[mikegarrison]

The original prediction was that it would re-enter several months ago. So I wouldn't worry too much about whether the predictions of last week were right on the minute or not.

[Serpens Solidus]

I found this:

Spoiler

 

EDIT: nvm, it was just stupid journalism: https://twitter.com/LexFazio/status/980617594884575233

 

Edited April 2, 2018 by Serpens Solidus
>:(

[MaxwellsDemon]

For general reference:

 

Science:  "The climate is changing."   (presents evidence)

Politics:  "So-and-so is the reason the climate is changing/not changing/etc."  (endless arguments)

 

That climate changes over time is an observed fact and is not political.   The whys, wherefores, and do-we-do-anything-about-it? is the political part.

 

This has been a public service announcement.