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Chang'e 3 landing tomorrow 13:40 UT, earlier than previously reported

Posted by Emily Lakdawalla

13-12-2013 11:20 CST

Topics: mission status, Chang'E program

According to numerous Chinese news reports, Chang'e 3's landing on the Moon is now scheduled to begin at 21:40 Beijing time on December 14, which is 13:40 UT or 05:40 PT. That's about two hours earlier than previously stated. Once deceleration begins, the whole process will take about 750 seconds. Here is a Xinhua news site in English that may contain news updates about the landing. It is possible that this CCTV website will contain a news feed. Chinese television coverage will begin at 11:00 UT. I am not sure that I will be able to cover this event live; I'm not feeling well and need the sleep! But if I do I will be watching for English language CCTV coverage here.

Some other bits of useful information:

Also, this interesting tidbit about plans for Lunar Reconnaissance Orbiter observations, from a comment on a previous Chang'e post: "LRO will be attempting to collect spectrographic data from the LAMP instrument as close to the landing time as possible, primarily to see the rocket plume and the dust kicked up from the landing. The camera will image the lander some time after the landing, but even at the spectacular resolution of the LRO Camera, there probably won't be much more than a blur to see."

In a previous post I included this infographic on the mission. Some very helpful commenters have translated its contents, and I'm including those translations below.

Chang'e 3 infographic
Chang'e 3 infographic

The long text at top:

  • Transfer segment: Chang'e 1: GTO to phasing orbit to trans-lunar injection (TLI) orbit.
    Chang'e 2: directly to TLI orbit
    Chang'e 3: over a ton heavier than Chang'e 2, directly to TLI orbit.
  • Lunar braking: Chang'e 3 is equipped with a newly-designed variable-thrust rocket engine to directly transfer the payload from trans-lunar injection orbit to the circular lunar orbit. In contrast, Chang'e 1 and 2 were transferred from trans-lunar injection orbit, to elliptical lunar orbit, then to the circular lunar orbit. This was due to limited fuel availability.
  • Soft landing: After 4 days in circular lunar orbit, Chang'e 3 will transfer to an elliptical lunar orbit with the perilune point at 15 kilometers and the aposelene point at 100 kilometers. Chang'e 3 will begin its descent at 15 kilometers at around 11:22PM-11:35PM 12/14/2013, [15:22-15:35 UT, 07:22-07:35 PT -- note these times are no longer correct]. The descent engine will be ignited at 15 kilometers to decelerate, above 2 kilometers it'll have pointed its main engine downward, below 2 kilometers it'll be slowly descending. At 100 meters the payload will be hovering without receiving control from Beijing. It'll utilize its camera and computer to identify the surface, and automatically select a plain to land on. At 4 meters the descent engine will turn off, and the payload will land with a free fall.
  • Exploring the Moon: after the soft landing, first the lander will charge and initialize the rover; then the rover will start the communication link with Earth control, unlock the locking mechanism, and move to the transfer mechanism (ladder). Then the rover will control the transfer mechanism to descend to the surface of the moon, and drive itself away from the lander. Yutu (jade rabbit, the pet of the lunar princess in Chinese folklore) will be separated from the lander at 4:38-6:21 12/15/2013 [20:38-22:38 UT, 12:38-14:38 PT -- not sure if these times will also shift earlier by about two hours]. The descent will only be around 2 meters but the entire process will take around 2 hours. Nine hours after the separation, the lander and the rover will capture some photographs of each other using the equipped cameras. Both are painted with the national flag, therefore, a color photo of the Chinese national flag on the moon can be captured.

The numbered series of diagrams:

  1. Begin active deceleration at an altitude of 15 kilometers (which is the periapsis altitude).
  2. Turn to landing attitude at an altitude of 2 kilometers. (Descending vertically from here?)
  3. At an altitude of 100 meters, stop and hover; use cameras to autonomously detect hazards and find a flat place to land.
  4. Descend from 100 meters to 4 meters using thrusters.
  5. Free-fall from an altitude of 4 meters to the surface.
  6. After soft landing, release the rover.

The diagram at right showing activities once on the ground:

  • Deploy solar panels
  • Establish communications
  • Unlock rover
  • Deploy rover mast and panels
  • Create panorama for rover navigation
  • Move to surface (about 350 minutes)
  • Do local exploration (about 30 minutes)
See other posts from December 2013


Or read more blog entries about: mission status, Chang'E program


jim oberg: 12/13/2013 11:33 CST

I'm optimistic for success, because from what I've seen of the enormously impressive Chinese effort to study other people's space experience [they seem to extract more usable information from American space failures than America itself has], the early US and USSR failures should for all intents and purposes count as 'China failures' too, in so far as they benefit from those experiences. The Chinese space team has repeatedly shown an uncanny ability to learn from other people's mistakes, in space technology. It's not magic, and I think they have enormous challenges in running a big program under the top-down all-wisdom-flows-from-the-mandarins philosophy enunciated in their periodic 'white papers'. But for a well defined technological challenge whose environment -- the lunar surface -- they understand far better than did either NASA or the Soviets in the 1960s, I find reasons to expect success. Just as I do, to a somewhat lesser extent, for a few Google Lunar X-Prize contenders.

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