Chinese Tiangong to Reenter Atmosphere in a Month

[Yazata]

Put on your hardhats, it will leave a mark if it falls on your head. It weighs 8 1/2 tons and is losing altitude at 6 km a week from air resistance.

Hard to predict exactly when or where it will fall or how much of it will make it back to the surface. But models suggest it's most likely to hit at 42.7 degrees north and south latitudes. In North America that's southern Oregon, Detroit/Windsor or upstate NY. In Europe it's northern Spain, Tuscany or Bulgaria. In Asia it's northern China, Vladivostok or Japan's island of Hokkaido. In South America it's southern Chile or Patagonia. It just grazes Hobart Tasmania and is near Christchurch NZ. It could also fall anywhere between those lines, but the extremes are the most likely.

(Jonathan McDowell calculates that it has a 99.9% chance of not hitting New Zealand, so keep calm and carry on, Kiwis.)

[Image: DXtgzx1V4AAhghE.jpg]

http://www.skyandtelescope.com/observing...-re-entry/

https://twitter.com/planet4589?ref_src=t...r%5Eauthor

Here it is with a Soyuz-like Chinese Shenzhou capsule mated to it.

[Image: DXtg9kgVAAEZ6Tk.jpg]

[C C]

Xi Jinping might have his fingers crossed for luck that a surviving good chunk of this national property lands in the ocean somewhere, so that China can construe it as a reason to claim and build an artificial island on the spot.

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[Yazata]

Jonathan McDowell writes:

"As tiangong descends, confusion remains widespread about what we can predict about its reentry. Remember that a 1 hour error in our guessed reentry time corresponds to an 27000 km (17000 mile) error in the reentry position. And currently our estimate has a 2 week uncertainty."

https://twitter.com/planet4589?ref_src=t...r%5Eauthor

[Yazata]

Here's the Chinese Manned Space Program's English-language Tiangong 1 page:

http://en.cmse.gov.cn/col/col1763/index.html

Latest estimates have it falling between March 30 (next Friday) and April 3 (a week from this coming Tuesday). Nobody can predict exactly where, since it's travelling at about 17,000 mph (orbital velocity) so even an hour's uncertainty in time of entry means a 17,000 mile uncertainty in position. At the moment it's a 5-day window. (120 hours x 17,000 miles) Most of the Earth is covered by water, so my guess is that it will probably fall in the ocean somewhere and everybody will be wondering where. Of course it (or at least large parts of it) could come through your roof too.

[Image: ESA1-800x492.jpg]

[C C]

Nothing much applicable here, but other times I shouldn't be lightly skeptical about information dispensed by CMS anymore than I would be by NASA. But the CCP's pervasive reach throughout Chinese media makes it a tad difficult.

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[Yazata]

Here is (by far) the best webpage that I've seen on Tiangong 1's reentry. It's from the Aerospace Corporation.

http://www.aerospace.org/cords/reentry-p...1-reentry/

They point out that this is by no means the largest man-made object to reenter the atmosphere. That honor goes to Russia's old Mir space station at 120,000 kg. What's creating excitement about this one is that Tiangong 1 has been out of control since 2016. Mir was deorbited in 2001 in a controlled fashion so as to ensure that it would fall safely into the sea. Nobody knows where this one will come down.

According to this graphic, Tiangong is currently above the northern Pacific and seems headed directly for Portland Oregon. But since it probably won't fall until the end of the week or early next week, I guess that the rain-soaked mud-weasels will dodge a bullet.

http://www.aerospace.org/CORDSuploads/Ti...yboard.png

[Syne]

According to this graphic, Tiangong is currently above the northern Pacific and seems headed directly for Portland Oregon. But since it probably won't fall until the end of the week or early next week, I guess that the rain-soaked mud-weasels will dodge a bullet.

Drats! MR could have made hay over that "sighting" for weeks.

[Yazata]

Nothing much applicable here, but other times I shouldn't be lightly skeptical about information dispensed by CMS anymore than I would be by NASA. But the CCP's pervasive reach throughout Chinese media makes it a tad difficult.

The English-language version of the Chinese Tiangong webpage sure doesn't have much to say. Just a report that it is at a particular altitude each day (always descending) and a statement that there were "no anomalies". (Apart from the damn thing crashing in a week and they've lost control of it.)

I expect that the Chinese leadership finds this embarrassing and doesn't want too much said. If anyone wants to know anything more about it, they need to read the commentary from outside China. (Much of which is probably invisible to internet users inside China because of the party's "Great Firewall of China".)

In a way I think that they are missing an opportunity. People all around the world are interested in this and many of us have learned more about the Chinese manned space program in in the last few days than we knew in the years previous. I don't sense that anyone is blaming China for losing telemetry contact with Tiangong. It's just one of those unfortunate things. Space is inherently risky.

The Chinese should use the opportunity that being the focus of world attention gives them.

[Yazata]

For those who don't know (I was one of them) 'Tiangong' means 'Heavenly Palace'.

As of now, the reentry time window has shrunk to 07:15 UTC (essentially Greenwich Mean Time) on April 1, 2018 (Easter Sunday!) plus or minus 20 hours.

I believe that Pacific Daylight Time (where I am) is UTC minus 7 hours. So this thing should be falling right after midnight Saturday, give or take almost a day. Saturday or Sunday.

http://www.aerospace.org/cords/reentry-p...1-reentry/

[Yazata]

Now it's 10:30 UTC on April first (Easter!) plus or minus 16 hours.