Monday, May 11, 2015

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.

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