Chang'e-3 lunar probe and rover, CZ-3B - Xichang, December 2013

[Steven Pietrobon]

Using Lunar orbit rendezvous (LOR) greatly increases the mass returned to Earth, a few hundred grams for the Russian Luna sample return missions compared to two kg for LOR. This is because you do not need to carry the 1 km/s of return propellant from Lunar orbit all the way down and back up again (a 4 km/s penalty).

Using Lunar orbit for the return also allows return from any point on the Moon. If using a single burn direct ascent like the Luna missions, you are restricted to certain areas of the Moon, I believe to be in the Eastern hemisphere.

[Phillip Clark]

Using Lunar orbit rendezvous (LOR) greatly increases the mass returned to Earth, a few hundred grams for the Russian Luna sample return missions compared to two kg for LOR. This is because you do not need to carry the 1 km/s of return propellant from Lunar orbit all the way down and back up again (a 4 km/s penalty).
Using Lunar orbit for the return also allows return from any point on the Moon. If using a single burn direct ascent like the Luna missions, you are restricted to certain areas of the Moon, I believe to be in the Eastern hemisphere.

My understand is that the restriction on the Luna 15 et al sample-return mission landing site longitude was because the ascent stage did not have a pitchover capability - the implication being that with this capability you could land elsewhere on the Moon.

I would have thought that including a separate Earth-return stage in selenocentric orbit would decrease the mass of the lunar sample being brought back because of the extra equipment required for the automatic rendezvous and docking - plus the additional stage structure itself.

[vill]

I thought, that doing lunar orbit automatic docking in sample return missions could mean also technology test, which can be greatly needed for manned missions. Don't know exactly why , but for me may be useful for precise testing of spacecraft and landing before actual human flight, or for orbital maneuvers without human presence like for constructing orbital station.

[Phillip Clark]

I thought, that doing lunar orbit automatic docking in sample return missions could mean also technology test, which can be greatly needed for manned missions. Don't know exactly why , but for me may be useful for precise testing of spacecraft and landing before actual human flight, or for orbital maneuvers without human presence like for constructing orbital station.

Docking tests with crews can be done in LEO, which is why I linked this approach to possibly technology-testing for a Mars mission.

But I still don't see why they would want to complicate and already-complex mission which only the Soviet Union has previously accomplished.

[vill]

Docking tests with crews can be done in LEO, which is why I linked this approach to possibly technology-testing for a Mars mission.

But I still don't see why they would want to complicate and already-complex mission which only the Soviet Union has previously accomplished.

Yes, this make sense. But if any docking on the lunar orbit is needed - and can be done without astronauts, it could be more cost effective. It depends on Chinese lunar architecture in first years I think.  For example adding new module to existing lunar orbital station, cargo flights to orbital station... I am not sure if this is real, even for first years after manned lunar landing. Later automatic dockings could be important...

So, if sample return mission is about testing docking technology too, it could mean, the Chinese lunar program plans to use it from the beginning (LOS in a few years after first manned flights?)

It depends on how difficult is to make automatic dockings in orbits further from earth for them; if it is largely more complicated they barely intend it just for robotic lunar exploration purposes and if possibly decreases lunar sample weight that could make worse scientific results than Soviet approach.

[Phillip Clark]

I have just been reviewing all of the animations of the Chang'e 3 mssion which I can find online - mainly at YouTube - and all of these depict a direct return from the lunar surface, like the Luna sample-return missions.

So, was the Chinese article wrong in what it said about a rendezvous in selenocentric orbit or have the Chinese decided the re-design and complicate the mission profile in the last three years or so?

[HappyMartian]

I have just been reviewing all of the animations of the Chang'e 3 mssion which I can find online - mainly at YouTube - and all of these depict a direct return from the lunar surface, like the Luna sample-return missions.

So, was the Chinese article wrong in what it said about a rendezvous in selenocentric orbit or have the Chinese decided the re-design and complicate the mission profile in the last three years or so?

"After Chang’e-3, Chang’e-4 will be launched. Together, they will complete the task of landing on the moon in the second phase of China’s lunar exploration program. According to Xinhua News, Chang’e-5 will be launched in 2017 and will send back samples of moon rock to earth for analysis from a depth of two meters."

From: Chang’e-3: China To Launch First Moon Rover In 2013  By By Srinivas Laxman   March 7, 2012   At: http://www.asianscientist.com/


"The provisional mission sequence stipulates that after launch, a four-module spacecraft will enter the lunar orbit. Thereafter, two modules will touch down on the moon’s surface. One of the modules will collect the soil samples and transfer them to the ascending module which will lift off from the lunar surface."

And, "After taking off from the moon, it will dock with the orbiting module. Once this process is completed, the lunar samples will be transferred to another module which will bring it back to earth."

From: China’s Unmanned Moon Mission To Bring Back Lunar Soil To Earth By Srinivas Laxman   March 21, 2012   At: http://www.asianscientist.com/topnews/china-unmanned-moon-mission-to-bring-back-lunar-soil-2012/


 

[Phillip Clark]

Since the Chinese originally announced Chang'e-1, Chang'e-2 and Chang'e-3 as being the lunar orbit, lunar landing/rover and sample return missions respectively, there is plenty of room for confusion since Chang'e 3 will be the first rover mission!

Maybe we should think of the original designators as being Phase 1, Phase 2 and Phase 3 respectively, with the flown Chang'e 1 and 2 being the Phase 1 missions and Chang'e 3 (and Chang'e 4? - even Chang'e 5??) being Phase 2 missions.

[snowhole]

Since the Chinese originally announced Chang'e-1, Chang'e-2 and Chang'e-3 as being the lunar orbit, lunar landing/rover and sample return missions respectively, there is plenty of room for confusion since Chang'e 3 will be the first rover mission!

Maybe we should think of the original designators as being Phase 1, Phase 2 and Phase 3 respectively, with the flown Chang'e 1 and 2 being the Phase 1 missions and Chang'e 3 (and Chang'e 4? - even Chang'e 5??) being Phase 2 missions.

Well the current Chang'e 2 was originally planned as a spare for Chang'e 1. Although Chang'e 1 was successful, they went ahead and let the spare fly as well and she became Chang'e 2 (taking the name originally designated for the rover). Maybe that's the logic behind the confusion.

[BUAA]

Since the Chinese originally announced Chang'e-1, Chang'e-2 and Chang'e-3 as being the lunar orbit, lunar landing/rover and sample return missions respectively, there is plenty of room for confusion since Chang'e 3 will be the first rover mission!

Maybe we should think of the original designators as being Phase 1, Phase 2 and Phase 3 respectively, with the flown Chang'e 1 and 2 being the Phase 1 missions and Chang'e 3 (and Chang'e 4? - even Chang'e 5??) being Phase 2 missions.

You're right that it is phase-1, 2 and 3 being orbiting, landing, and sampling returning respectively.

Each phase has two identical spacecraft built, one being the flying example and the other backup.

With Chang'e 1 successfully orbiting the Moon, there was actually no need to launch Chang'e 2. However, the programme decided to launch it nevertheless, and called it a "Phase-II" mission, a pathfinder for the subsequent Chang'e 3 lunar landing mission.

There was also media report about the first mission in the third-phase being Chang'e 5. So again Chang'e 4 is a back-up spacecraft. I would't be surprised if the mission also goes ahead.

[plutogno]

I think you are confusing phases of the program with missions. Phase 1 was the orbiter, phase 2 the lander and phase 3 the sample return, but the Chinese never stated that there would be a single mission for each phase. In fact, I remember a paper published even before Chang'e 1 was launched where they discussed flying TWO orbiters... now if I could remember where I saw that...

[plutogno]

the flight of 1 or 2 orbiters as the first phase of the Chang'e project was mentioned as early as 2004 in this abstract of a presentation to that year's ILEWG meeting
http://www.spaceagepub.com/pdfs/Ouyang.pdf

[Galactic Penguin SST]

Well I've reviewed the presentation by Ouyang Ziyuan at the China Academy of Science in June, and it has a list of instruments to be carried on board the lander and the rover. Three of the instruments are definitely worth mentioning:

1. The lander will carry an optical telescope (probably not that big, around a dozen cm in diameter) that would conduct the first ever astronomical observation from the lunar surface (well, the later Apollo J-class CSM came rather close....). This telescope will operate in the near UV region, and will target close binary stars, active galactic nuclei, short-period variable stars etc.

2. Also on the lander is a far UV region camera that will observe the 30.4 nanometer band radiation from the Earth's ionosphere, another first in lunar exploration. This will monitor the effect of space weather, solar activity, Earth's geomagnetic field and particle streams on the Earth's ionosphere.

3. The rover will carry a radar on it's bottom side, allowing for the first direct observation of the structure and depth of lunar soil down to 30 meters deep and the lunar crust structure down to a depth several hundred meters.

Other instruments include:

Lander: 3 x panoramic cameras, 1 x descent camera, 1 x extensible lunar soil probe, 1 x lander engineering package, 1 x lander data controller

Rover: 2 x panoramic cameras, 2 x navigation and engineering camera sets, 1 x alpha particle X-ray spectrometer, 1 x infrared spectrometer, 1 x lander engineering package, 1 x lander data controller.

The lander phase is rather conventional, but it includes a 100 second hovering phase for the lander to take photos of the landing area and find a flat spot for landing.

Sources:

Video of the presentation: http://www.cas.cn/zt/hyzt/16thysdh/zb/ (CE-3 part starts at 208 minutes)

http://www.9ifly.cn/forum.php?mod=redirect&goto=findpost&ptid=451&pid=166465

Meanwhile, the engineering model of CE-3 was transported to XSLC in June for practices of the launch campaign, still on target for launch next year. This is one of the reasons why no launches were scheduled from Xichang last month.

(source: http://www.9ifly.cn/forum.php?mod=redirect&goto=findpost&pid=210070&ptid=451)

[Phillip Clark]

On Apollo 16 an U-V telescope was set up on the lunar surface. to do a survery while the crew were wandering around.

[Dalhousie]

One of the Lunokhods carried a french telescope as well. 

The Lunokhods also reported quite bright skies, suggesting suspended dust, it is important for missions like Chang'e 3 to determine how good the lunar surface is for telescopic observations.

The geological backage sounds great - GPR, XRS, penetrometer.  I am really looking forward to these.