Author Topic: LIVE: Chang'e-2 (China's second lunar probe) - Long March 3C - October 1, 2010  (Read 192455 times)

Online plutogno

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Online plutogno

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The video shows that the possible targets for the planned Chinese asteroid fly-by mission are as follows:

according to another forum, the last lines (in red) mention a second exploration phase consisting of a main belt asteroid sample return. can you confirm?

Online plutogno

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another question (sorry, CE2 for me is the Chinese space news of the moment, I'm not interested in SZ9...)
I understood that the Tukmit, Apophis and 1996 FG3 are three possible targets of a dedicated asteroid mission, but Rui's blog http://astropt.org/blog/2012/06/14/change-2-a-caminho-de-toutatis/ suggests that they may be further targets for CE2. so which is right?

Offline yaohua2000

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Re: plutogno
1. Yes.
2. Rui is wrong.

Let me translate the slide in post #238:

Quote
(3) 小行星探测任务
一、首次近地小行星探测任务:
精确确定小行星轨道和相关特性,
评估其撞击地球可能;同时开展
科学探测研究。

探测目标 | 物理参数 | 探测方式 | 探测时间
-----------------------------------------
12711号 (Tukmit, 1991 BB) | 光谱型:X/直径:X/自转周期:X | 飞越探测 | 2018.8
99942号 (Apophis, 2004 MN4) | 光谱型:X/直径:X/自转周期:X | 伴飞探测 | 2020.4 - 2020.9
175706号 (1996 FG3) | 光谱型:X/直径:X/自转周期:X | 伴飞探测 | 2023.8 - 2023.12

二、第二次小行星探测 — 主带小行星采样返回探测

Translation:
Quote
(3) Asteroid exploration mission(s)
1. First time near-Earth asteroids exploration mission(s):
- Precisely determine asteroid orbit and related features,
- Evaluate their possibilities hit the Earth; And perform
- Scientific exploration research

Exploration target | Physical parameters | Exploration method | Exploration time
-----------------------------------------
12711 Tukmit | Spectral type: X / Diameter: X / Rotation period: X | Flyby exploration | August 2018
99942 Apophis | Spectral type: X / Diameter: X / Rotation period: X | Rendezvous exploration | April 2020 – September 2020
175706 (1996 FG3) | Spectral type: X / Diameter: X / Rotation period: X | Rendezvous exploration | August 2023 – December 2023

2. Second time asteroid exploration — Main-belt asteroid sample return exploration

I use "mission(s)" as Chinese language does not have plural words. It can be one probe for all the three asteroids, or three separated probes. Not possible to tell from the slide.
« Last Edit: 06/15/2012 08:09 PM by yaohua2000 »

Online Satori

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Re: plutogno
1. Yes.
2. Rui is wrong.

ah! Thank you for the correction! I thought Cheng'e-2 would be redirected to other targets after Toutatis.

Online plutogno

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while waiting for details and news on the Toutatis mission (note that it's been more than a week since the story was leaked, and Chinese mainstream press has not yet picked it up), I have found an interesting if quite technical paper on Moon-to-L2 navigation
http://info.scichina.com:8083/sciFe/EN/abstract/abstract507363.shtml

Online plutogno

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while everybody is looking at SZ-9 and its expoits, I continue to dig into the Chinese technical literature for hints at the extended mission of CE-2.
Here are two different extended missions that have been studied and non selected:

- A mission to the lagrangian points of the Earth-Moon system
http://tech.scichina.com:8082/sciEe/EN/abstract/abstract505028.shtml
Quote
Trajectory design for the Moon departure libration point mission in full ephemeris model
The lunar probe may still have some remaining fuel after completing its predefined Moon exploration mission and is able to carry out some additional scientific or technological tasks after escaping from the Moon orbit. The Moon departure mission for the lunar probe is the focus of this paper. The possibility of the spacecraft orbiting the Moon to escape the Moon's gravitational pull is analyzed. The trajectory design for the Earth-Moon system libration point mission is studied in a full ephemeris dynamical model, which considers the non-uniform motion of the Moon around the Earth, the gravity of the Sun and planets and the finite thrust of the onboard engine. By applying the Particle Swarm Optimization algorithm, the trajectory design for the transfer from the Moon-centered orbit to the L1 halo orbit, the station-keeping strategies for the Earth-Moon halo orbit and the construction of homoclinic and heteroclinic orbits are investigated. Taking the tracking conditions and engineering constraints into account, two feasible schemes for the Moon departure libration point mission for the lunar probe are presented.

- An asteroid mission from lunar orbit
http://phys.scichina.com:8084/Jwk_sciG_en/EN/abstract/abstract502540.shtml
Quote
Design and optimization of a trajectory for Moon departure Near Earth Asteroid exploration
The lunar probe often has some remaining fuel on completing the predefined Moon exploration mission and may carry out some additional tasks from the Moon orbit using the fuel. The possibility for the lunar probe to escape from the Moon and the Earth is analyzed. Design and optimization of the trajectory from the Moon orbit to the Near Earth Asteroids (NEAs) using the spacecraft’s residual fuel is studied. At first, the semi-major axis, inclinations and the phase relations with the Earth of all the numbered NEAs are investigated to preliminarily select the possible targets. Based on the Sun-centered two-body problem, the launch window and the asteroid candidates are determined by calculating the minimum delta-v for two-impulse rendezvous mission and one-impulse flyby mission, respectively. For a precise designed trajectory, a full ephemeris dynamical model, which includes gravities of the Sun, the planets and the Moon, is adopted by reading the JPL ephemeris. The departure time, arrival time, burning time duration and thrust angles are set as variables to be designed and optimized. The optimization problem is solved via the Particle Swarm Optimization (PSO) algorithm. Moreover, two feasible NEA flyby missions are presented.

as I pointed out in a post to the unmannedspaceflight.com forum, the choice of Toutatis over other near-Earth objects (the latter paper mentions an Apollo and an Aten asteroid, 190491 and 162421) is a clever one. Toutatis has been detected by radar on every Earth flyby since 1992 (encounters repeat at 4-years intervals), and its orbit is thus known to an accuracy probably unique among such small objects. It turns out that its position on 6 January 2013 is known with an uncertainty of just a few kilometers, meaning that even in the absence of a moving-object detection and tracking software (which CE-2 probably does not possess), it should be possible to image and take other measurements of it simply by aiming cameras and spectrometers at the spot in the sky where it is predicted to be.

Online plutogno

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at last the story has been picked up by Chinese news sites!
http://tech.sina.com.cn/d/2012-06-27/14427317706.shtml
nothing new as far as I can tell from the Google translation, beside the first mention of a planned flyby distance of 1000 km. I also find it interesting that they mention a flyby near the end of this year or early next year, as if the date was not yet fixed

Offline yaohua2000

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at last the story has been picked up by Chinese news sites!
http://tech.sina.com.cn/d/2012-06-27/14427317706.shtml
nothing new as far as I can tell from the Google translation, beside the first mention of a planned flyby distance of 1000 km. I also find it interesting that they mention a flyby near the end of this year or early next year, as if the date was not yet fixed

1000 km is a mistake made by the journalist, who actually wanted to write a flyby distance of 1000,0000 km from the Earth. The same journalist also says L2 is 150 km from the Earth, instead of 150,0000 km. Furthermore, the journalist didn't make an interview with Ouyang. Everything was from the same presentation that we already have.

Quote
去年6月9日,“嫦娥二号”再次开始新的旅程,奔向150公里的拉格朗日2点;

欧阳自远介绍,“嫦娥二号”于2012年4月15日受控飞翔距离地球大约1000千米深邃的太阳系空间

“嫦娥二号”搭载的CCD相机如果以1000公里的距离飞越4179号小行星

Very poorly written report indeed.
« Last Edit: 06/28/2012 09:20 AM by yaohua2000 »

Online plutogno

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thanks for your input yaohua2000!
actually, on 6 Jan 2012 Toutatis will be 28.2 million km from Earth, and even on its closest approach to Earth in December it will be no closer than 6.9 million km. I have seen the distance of 1 million km in other reports, but I don't understand what it is supposed to mean...

Offline yaohua2000

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thanks for your input yaohua2000!
actually, on 6 Jan 2012 Toutatis will be 28.2 million km from Earth, and even on its closest approach to Earth in December it will be no closer than 6.9 million km. I have seen the distance of 1 million km in other reports, but I don't understand what it is supposed to mean...

I did some gravitational simulations a few days ago, given the initial location of Chang'e 2 at L2, I can't find a solution with a reasonable delta-v budget to rendezvous with Toutatis on January 6, 2012. The most likely date of a flyby should be in late December.

I am not an expert in this field but it looks like they are trying to follow the interplanetary superhighway concept that proposed by 罗闻宇?

Online plutogno

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I suspect that there will be Moon or Earth flybys involved, like NASA did on the International Cometary Explorer in the 80s...

Offline ChrisC

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FYI, Emily Lakdawalla at the Planetary Society provided a nice link over to this thread in a planetary.org blog post, as the place to get Chang'e-2 updates!
« Last Edit: 07/07/2012 03:10 AM by ChrisC »
NASA TV in HD:  history, FAQ and latest status

Online plutogno

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unfortunately, even after almost a month, there is almost nothing on the mission on the Chinese websites.
Interestingly, someone pointed out on the 9ify forum http://www.9ifly.cn/thread-9843-106-1.html that the mission could be a test of the Chinese deep space network (separated from the lunar tracking network, apparently), which may be true as they could not test it on YH-1 at Mars.
note also that JPL gives 5 January as the flyby date http://echo.jpl.nasa.gov/~lance/radar.small.body.mission.targets.html, but this is probably just a Chinese time zone issue.
BTW, with all the hype on SZ-9 finally subsiding, will Xinhua or any other Chinese news agency finally release some solid details on the mission? please...

Online plutogno

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this seems to have gone unreported: there was a meeting at the Purple Mountain Observatory last January on Chang'e 2 extended mission to asteroids

http://www.cas.cn/hzjl/ydhz/hzdt/201201/t20120113_3427830.shtml

Online plutogno

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there was an interview with Ouyang Ziyuan published in some Chinese news sites today, speaking about Chinese lunar exploration. see for example
http://www.tianshannet.com.cn/edu/content/2012-07/23/content_7052742.htm
nothing really new, except for an anecdote on a gift Apollo 17 pebble that the Chinese removed from its plexiglas case during the 1970s, cut in half and analyzed to verify that it was indeed a Moon rock.
In the same interview Ouyang states that the CE-2 asteroid flyby will take place "in March (3月) next year". I am puzzled...

Online plutogno

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repeated on some sites today: flyby "probably" on 1 March (3月1日) next year

http://news.sina.com.cn/c/2012-07-25/021924837262.shtml

Online plutogno

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re-posted from unmannedspaceflight.com:
at last some hard data on CE-2
http://www.projectpluto.com/pluto/mpecs/cheprobe.htm
the probe appears to be, from optical observations, on an Earth-like 1.022 x 1.035 AU orbit with a period of 381 days and an inclination of 0.24 degrees that will intersect Toutatis' path on 13 December, one day after its closest approach to Earth.

Online plutogno

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a blog article by Bill Gray describing how CE-2 was recovered by terrestrial telescopes, and how the 13 December flyby date was determined
http://www.planetary.org/blogs/20120825-change-2-the-full-story.html
« Last Edit: 08/25/2012 04:30 PM by plutogno »

Online plutogno

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two papers to be presented at this year's IAC:

An Extended Mission of Chang’E-2 From Sun-Earth L2 point to Asteroid: Design and Analysis
http://www.iafastro.net/iac/paper/id/15114/summary.lite/

Low energy trajectory optimization for CE-2’s extended mission after 2012
http://www.iafastro.net/iac/paper/id/15724/summary.lite/