One month left for Tiangong-1 [UPDATED]

Note: a daily updated post with reentry estimates for Tiangong-1 is here.

image (c) Alain Figer, used with permission

The beautiful image above (used with kind permission) was made by Alain Figer and shows the Chinese Space Station TIANGONG-1 over the French Alps on 27 November 2017.

Tiangong ("Heavenly Palace") 1 was launched on 29 Sept 2011. It was the first Chinese Space Station and was visited by Taikonauts twice, first by the crew of Shenzou 9 in June 2012 and then by the crew of Shenzou 10 in June 2013: six Taikonauts in total.

All eyes are currently on this Chinese Space Station, as it is about to re-enter. Since the station was shutdown in 2016, it has steadily come down, especially so the past year and months. Its orbital altitude has currently descended below 250 km (it currently is ~240 km, with apogee at 251 km and perigee at 229 km on 2018 March 13):

click diagram to enlarge

click diagram to enlarge

Using SatAna and SatEvo, and under the assumption that the re-entry will be completely uncontrolled, I currently estimate it to re-enter one month from now, somewhere between April 7 and April 21  April 1 and April 12.

EDIT:  daily updated re-entry predictions are in a dedicated post here

The station has an orbital inclination of 42.8 degrees, and hence can come down anywhere between 42.8 N and 42.8 S. The map below shows the area that is at risk:

click map to enlarge

Note that newspaper accounts (e.g. this one) that single out a particular area as being at particular risk, are nonsense: At this stage, a month before re-entry, it is impossible to pinpoint a region. That will only be possible during the hours just before actual re-entry (and even then...).

The station has a mass of about 8500 kg and measures 3.35 x 10.4 meter. It is hence a large and heavy object, which is why this re-entry is of concern. It is likely that parts will survive the re-entry and reach Earth surface intact.

Land masses inside the risk zone include southern Eurasia, Australia, Africa, South and Middle America and the United States. It is however most likely that the re-entry will be over an ocean.

As can be seen from the map above, my own country, the Netherlands, is well outside the risk zone.

I will follow the orbital evolution and re-entry predictions for Tiangong-1 on this blog as they evolve.

Tiangong-1 image on 18 July 2017 by Alexandre Amorim from Brazil
this is a stack of 4 separate images
(image (c) Alexandre Amorim, used with permission)

NOTE: new reentry estimates, updated daily, are consolidated in this new blog post.

Chinese CZ-11 rocket stage impacts Myanmar Jade quarry (updated)

On November 9 at 23:42 UT (November 10 in local time), China launched a Long March 11 (CZ-11) rocket from Jiuquan on a south-bound trajectory, lofting the XPNAV satellite into orbit.

The object (image from the Myanmar Times)

Shortly after this, an object came crashing out of the sky in Myanmar, impacting in a Jade quarry near Hmaw His Zar village near Hpakant in Kachin Province. Photographs of the object can be seen in the news stories here and  here. The image in the first link is the best in terms of showing shape and size.

The object is reportedly ~4 meter long and ~1.5 meter wide (reports differ slightly). In one of the images, it is clear that it is different in diameter at both ends, the shape being that of a barrel with a tapering segment on it.

Size and shape conforms to (what I assume is) the second stage of the CZ-11 (edit: might in fact be the 3rd stage), which is about ~4 meters long and about 2 meter diameter at one side, tapering to about 1.4 meter diameter at the other side. A drawing of the rocket's elements is here and another, perhaps more accurate rendering is here (the drawings differ somewhat, hence my confusion on whether this is the 2nd or 3rd stage. From the second rendering, it looks to be the 3rd rather than the 2nd stage).

Click map to enlarge

As can be seen in the map above, last Wednesday's Chinese launch trajectory lines up well with the reported location of the impact in Myanmar.  So it almost certainly is the 2nd (3rd?) stage of the CZ-11 rocket used for this launch.

[edit 12 Nov 2016: to be clear, the line on the map is a projection of the orbital plane of the XPNAV satellite at the moment of launch, as a proxy for the launch trajectory. You can see it lines up with both the Jiuquan launch location and the location where the object came down in Myanmar].


UPDATE: Jeffrey Lewis ("The Arms Control Wonk") pointed me to this Chinese CNTV footage about the recent launch that shows various parts of the CZ-11 rocket. From 0:35 onwards, one of the stages shown visually clearly is a match for the Myanmar objects:



Here are a few stills from the footage, compared to one of the images of the Myanmar object. The red semi-transparent boxes indicate which stage matches in terms of shape and details such as the round hole halfway the hull:

click to enlarge

(editted 12 Nov: added images and text, noted the 2nd/3rd stage potential confusion)

Tracking distant space debris: more Chang'e 2 r/b observations

In my previous post I related how on May 7 a distant piece of Space junk was briefly mistaken for a Near Earth Asteroid. It concerned 2010-050B, the upper stage of the Long March 3C rocket that launched the Chinese Lunar mission Chang'e 2 in October 2010. This upper stage is moving in a trans-Lunar orbit, with apogee up to almost two Lunar distances away from Earth. The rocket stage is 12.4 by 3 meters large.

Yesterday May 10, I obtained new images of the object, using the 0.61-m Cassegrain telescope of Sierra Stars Observatory in California, USA. Above is an animated GIF of the images. My resulting astrometric data are here.

The object was near mag. +15.3, at a distance of almost 518 800 km at that time. For a comparison: the distance to earth of the moon varies between about 356 400 and 406 700 km. It is quite cool to image space junk at this large a distance!

Click image to enlarge

Using my May 10 observations combined with the May 7 observations by the Catalina Sky Survey (MPC 703) and Peter Starr in Warrumbungle (MPC Q65), I compute the following orbit for the object:

Orbital elements: 2010-050B Chang'e 2 r/b

Perigee 2015 May 22.689019 +/- 0.00747 TT 
= 16:32:11 (JD 2457165.189019) 
Epoch 2015 May 7.0 TT = JDT 2457149.5       Find_Orb 

M 198.75910 +/- 0.037        
n 10.27730942 +/- 0.00562

a 452220.817 +/- 165 km    Peri. 151.22410 +/- 0.028 
e 0.2197903 +/- 0.000308   Node 226.29285 +/- 0.00006
i 41.13389 +/- 0.00028 
  
q 352827.032 +/- 267 km    Q 551614.602 +/-  68 km       
P 35.03 d        H 28.1 

From 23 observations 2015 May 7-10; mean residual 0".307.

In TLE form:

Chang'e 2 r/b                                 352827 x 551615 km 
1 00000U         15127.00000000  .00000000  00000-0 00000-0 0 09
2 00000 41.1326 226.5090 2163618 150.9650 199.0248 0.02835833 01

For those people with access to a  sufficiently large instrument that want to try it themselves: efemerids for the object can be obtained here.

I plan to include this object in my periodic observations of distant satellites.