Author Topic: LIVE: TianGong-1 JSLC CZ-2F (T1) launch September 29, 2011, and future events  (Read 508476 times)

Online Olaf

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https://twitter.com/esaoperations/status/976809497015603202
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Updated #Tiangong1 forecast from ESA's Space Debris Office: The current estimated window is ~30 March to ~2 April; this is highly variable http://blogs.esa.int/rocketscience/2018/01/12/tiangong-1-reentry-updates/

Offline eeergo

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Amazing TG-1 radar images from Germany's land-based TIRA radar: https://twitter.com/Fraunhofer_FHR/status/976436268228890624

Quote
Weltweit einzigartige Radarabbildungen von Tiangong-1!
Forscher des Fraunhofer FHR begleiten Wiedereintritt der chinesischen Raumstation Tiangong-1
https://t.co/MKCeACtJzS
« Last Edit: 03/22/2018 01:11 PM by eeergo »
-DaviD-

Offline AStick

My "friend" is looking at 31 Mar- 1 Apr with medium confidence on the 1st.  My other "friend" agrees so plan on an April Fool's party courtesy of the Chinese.  Of course, any solar flare can cause that estimate to shift.

Offline Cristiano

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The reentry interval is now very narrow, only +/-1.3 days:



[original size]

An interesting result could be this:



[original size]

which shows the possible reentry orbital plane.

When compared to the same graph for March 18 simulation, they almost exactly overlap:



[original size]

but the updated graph shows much less spread.
The same locations (from today’s simulation) in two orthographic projections:



[original size]



[original size]

EDIT: Google Earth kmz file (179 kB); don’t use the WEB version, because it’s too slow:
http://cristianopi.altervista.org/Tiangong/TIA1-2018-03-24_MC_GE.kmz
If you don’t see the points, just zoom a bit.
« Last Edit: 03/25/2018 09:42 PM by Cristiano »

Online FutureSpaceTourist

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This is quite a difference:

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China's human spaceflight agency had Tiangong-1 in 208.1 x 224.3 km x 42.65° orbit for March 25. US Space Surveillance Network reported 203 x 222 km x 42.75 degrees.

https://twitter.com/AJ_FI/status/978158201026895872

Online Phillip Clark

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This is quite a difference:
Quote
China's human spaceflight agency had Tiangong-1 in 208.1 x 224.3 km x 42.65° orbit for March 25. US Space Surveillance Network reported 203 x 222 km x 42.75 degrees.
https://twitter.com/AJ_FI/status/978158201026895872

They are using different Earth models for calculating altitudes, etc.
I've always been crazy but it's kept me from going insane - WJ.

Offline Cristiano

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This is quite a difference:

Quote
China's human spaceflight agency had Tiangong-1 in 208.1 x 224.3 km x 42.65° orbit for March 25. US Space Surveillance Network reported 203 x 222 km x 42.75 degrees.

https://twitter.com/AJ_FI/status/978158201026895872

If I do the calculation with the TLE 18084.87551043 (2018-03-25 21:00:44 UTC), I get 208.246 x 224.963 above a sphere with R= 6371 km (the mean Earth radius) and 202.121 x 221.361 above the WGS 84 ellipsoid.

42.65 is the mean inclination wrt the mean equator J2000, while 42.75 is the mean inclination in the TEME reference frame.

Offline Steven Pietrobon

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If I do the calculation with the TLE 18084.87551043 (2018-03-25 21:00:44 UTC), I get 208.246 x 224.963 above a sphere with R= 6371 km (the mean Earth radius) and 202.121 x 221.361 above the WGS 84 ellipsoid.

NASA normally uses the equatorial radius of 6,378,165 m. That was also the reference used by the R.A.E.
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Online lamid

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application
https://www.satellite-calculations.com/TLETracker/SatTracker.htm
tiangong-1 TLE 18084.87551043
Altitude at Perigee   km   
200.87848383724395
Altitude at Apogee   km   
220.86293815869976
Inclination   deg   
42.7436

Offline limen4

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Fraunhofer FHR is now now providing an animation of Tiangong-1 movement based on TIRA radar images.

https://www.fhr.fraunhofer.de/content/dam/fhr/de/images/D_Pressemedien/2018/Fraunhofer_FHR_Tiangong1_20180111_854x480.mp4

Offline Cristiano

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application
https://www.satellite-calculations.com/TLETracker/SatTracker.htm
[...]

I read: "NOTE: This tracker uses a simplified calculation of satellite position which is NOT as accurate as trackers using SDP/SGP models !!". There are dozens of sites and programs for those calculations, why do you use that site?
Also, I read "Inclination ... from TLE", "Right Ascension of Ascending node ... from TLE", ... which means that the values are read directly from TLE, while TLEs must be used only with the intended propagator (SGP4/SDP4).

Offline eeergo

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Fraunhofer FHR is now now providing an animation of Tiangong-1 movement based on TIRA radar images.

https://www.fhr.fraunhofer.de/content/dam/fhr/de/images/D_Pressemedien/2018/Fraunhofer_FHR_Tiangong1_20180111_854x480.mp4

I have swiftly received an answer from Dr Leushacke upon the question I emailed him on how to interpret this rotation:

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As part of our work on Tiangong-1 re-entry we also estimate the actual attitude motion parameters for ESA. At the time the radar movie was produced, the rotation (about a vertical body axis) has been around 1.5 deg/s. Since then it has slightly increased to about 1.9 deg/s.


That is, TG-1 would be completing a rotation every 4 minutes at the time the movie was made (now every ~3m10s), so the movie is sped up by a factor of ~24.
« Last Edit: 03/27/2018 10:05 AM by eeergo »
-DaviD-

Offline Cristiano

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I have swiftly received an answer from Dr Leushacke upon the question I emailed him on how to interpret this rotation:
Quote
As part of our work on Tiangong-1 re-entry we also estimate the actual attitude motion parameters for ESA. At the time the radar movie was produced, the rotation (about a vertical body axis) has been around 1.5 deg/s. Since then it has slightly increased to about 1.9 deg/s.

Has he also given an explanation for that acceleration? Or could anyone give an explanation?

Offline eeergo

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He didn't but in principle it can well be a direct consequence of higher drag.
-DaviD-

Online Phillip Clark

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The BBC has run this story - it doesn't contain anything new though.

http://www.bbc.co.uk/news/world-asia-china-43551144

I cannot understand why so many online stories about the Tiangong decay use a picture of Shenzhou instead of Tiangong.   Presumably the authors don't know anything about the Chinese space programme and therefore do not know the difference between Shenzhou and Tiangong.
I've always been crazy but it's kept me from going insane - WJ.

Offline eeergo

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He didn't but in principle it can well be a direct consequence of higher drag.

Rotation measured a few hours ago to be up to 2.2º/s (a revolution every ~2m45s). New video https://twitter.com/Fraunhofer_FHRe/status/978616595609157635
-DaviD-

Online lamid

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My prediction for Tiangong1
02.04.18 11:05

« Last Edit: 03/27/2018 01:48 PM by lamid »

Online lamid

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There are dozens of sites and programs for those calculations, why do you use that site?
...
I use it a long time ago
Recommend which website would be more appropriate

Offline Cristiano

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Rotation measured a few hours ago to be up to 2.2º/s (a revolution every ~2m45s). New video https://twitter.com/Fraunhofer_FHRe/status/978616595609157635

It seems that the rotation is in the opposite direction; just an optical illusion?

Offline Cristiano

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[...]
Recommend which website would be more appropriate

I can't recommend any particular site, but almost all the sites use the proper propagator to calculate the orbital elements.
« Last Edit: 03/27/2018 02:56 PM by Cristiano »

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