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More flags and banners, with the spacecraft and rocket processing teams:pic.twitter.com/1PwQJPaXVT
Conflicting insider sources with another reliable one saying there will be some coverage on launch day: https://m.weibo.cn/status/JuikP1PG7 …
At the launch pad: https://twitter.com/Longmarch13/status/1328528387204292608 …
(rant) Well I was trying to write up a step-by-step walk through of Chang'e 5 from launch to Earth touchdown. Turns out not only I don't have parameters of its science instruments, there's only ONE list of it in a 2017 paper in Chinese! If anyone have them, please let me know.
(rant) There are also many holes in my understanding of the lunar sample transfer process. If someone have good diagrams (especially the sample storage of the ascent stage, plus how samples move from ascent stage to the Earth return capsule), please let me know too.
OK so, since several days of additional waiting from me failed to turn up more recent info, here's my walk through of the mission that, unlike other sample return missions, will be all over in 23 Earth days. And it's HARD. Lots of things can go wrong in a blink.
Firstly, the ride to the Moon. While scoring successes w/ last Dec.'s RTF, the next-gen crew S/C (w/o 2nd stage) in May and sent TW-1 to Mars in July, the Long March 5 is still an inexperienced rocket. With every of its launches flagships, the pressure must be intense every time.pic.twitter.com/sX4LDc80C5
Look at the engines. The YF-77 "Chinese Vulcain" on the core stage scored 3 good flights since the July 2017 failure and lots of teething troubles in testing. The YF-75D on the upper stage (expander cycle & not the CZ-3B's gas generator YF-75) had just *2* good flights!
(on the 1st launch in Nov. 2016 the YF-75D under-performed & required the YZ-2 U/S to correct it). The RP-1 YF-100 has had 5 more launches under LM-6/7, but still it's pretty young. Then there's GNC and other issues etc. The ~30 minutes through S/C sep. will be a long wait.
After separation the whole spacecraft will be on a direct trajectory towards the Moon.
@coastal8049 made some calculations based on prior mission timelines and estimate the LOI will be around 4.5 days after launch, probably ~14:45 UTC on Nov. 28: http://satobs.org/seesat/Nov-2020/0156.html …pic.twitter.com/nPhw3bf9hh
What goes afterward is a bit hazy as I have never saw any detailed description of the mission timeline after this, but the spacecraft should stay in an unknown lunar orbit awaiting the sun to rise at the landing site, then separates from the orbiter and land.pic.twitter.com/VsMd4ORf5f
We still have no idea when it will land - I have seen Nov. 30 mentioned once but early Dec. is possible - but while the Chinese have 2 successful ones already, the 2 failed Moon landings still remind people that GNC is a harsh mistress.pic.twitter.com/KyOdQlpXpi
With the lander probably a bit different from the ones used on Chang'e 3/4, even this part will still be a challenge to nail down. All these parts will apparently be observed by a descent camera like the last 2 landings, though the only official source is from a Chinese paper.pic.twitter.com/4STjkSxoEr
Now the surface operations is rather spotty in terms of public info. It took me quite a long time to nail the scientific instrument suite that would help in the sampling: - Panoramic Camera (PCAM) - Lunar Mineralogical Spectrometer (LMS) - Lunar Regolith Penetrating Radar (LRPR)
The only mention of the PCAM is the paper excerpt below - I'm not even sure where they are located, perhaps it's the rotating platform in the picture on the descent stage. I can't find their technical parameters either... (https://meetingorganizer.copernicus.org/EGU2016/EGU2016-3858.pdf …)pic.twitter.com/xZz5YUUurV
The LMS is apparently a visual/near infrared spectrometer - according to https://meetingorganizer.copernicus.org/EGU2016/EGU2016-5644.pdf … this is similar to the VIS/NIR Imaging Spectrometer (VNIS) on the Chang'e 3 rover w/ some modifications. I can't find where it is (same as PCAM?) or its technical parameters.
The LRPR works at 2 GHz frequency under the bottom of the descent stage and maps the regolith structure beneath it for ease of sampling/drilling analysis. Luckily we do have a detailed paper regarding its principles with photos: https://www.essoar.org/pdfjs/10.1002/essoar.10504784.1 …
As for the most important part, sample retrieval, the landing site near Mons Rumker in Oceanus Procellarum is of new geological importance not seen in previous lunar samples. @elakdawalla has it summarized here:https://www.patreon.com/posts/change-5-lunar-43869582 …
And sorry for the interruption, but a certain insider has reported important timings of the mission! Launch time: 20:25 ~ 21:15 UTC on November 23 Landing time: Probably ~20:30 UTC on November 29 (base on MCC screen shots during final rehearsal) Source https://m.weibo.cn/u/5616492130 pic.twitter.com/f1SnOA8ZeD
Also it appears that after McGregor Texas, Wenchang is also a major habitat of Rocket Cows (TM):pic.twitter.com/GYTWHDV0fr
It seems that I won't have time to finish this overview until half a day later so I'll just leave you with views of the pad from last night and right now: https://twitter.com/Longmarch13/status/1330473033316802562?s=19 …
Someone found this paper on the Lunar Mineralogical Spectrometer (LMS) and it's great! It's fixed to one side of the descent stage and points towards the soil sampling area. https://www.spiedigitallibrary.org/journals/Journal-of-Applied-Remote-Sensing/volume-13/issue-2/027502/----Custom-HTML----Spectrometers/10.1117/1.JRS.13.027502.pdf …
Not much news yet, but the lenses are ready for tonight: https://twitter.com/Longmarch13/status/1330784069962117120 …
Sun currently setting at Wenchang: https://twitter.com/Longmarch13/status/1330818792213995520 …
So back to the mission, Chang'e 5 will combine scooping and drilling to obtain lunar (sub)surface samples, aiming for least 2 kg & w/ capacity for 4. Three-quarters by mass will be via scooping on the surface, with 1/4 from the drill that will reach 2.5 meters deep.
Like the Soviet LSR missions of the 1970s, the deep drilling will provide layered sub-surface samples of the lunar crust. Detailed description of drilling bit and sample sealing can be found at https://ieeexplore.ieee.org/abstract/document/8607979 …. I'm not sure how samples would be put into the ascent stage.pic.twitter.com/T2V1Reh5tf
The other method of sampling will be via a double scoop on the end of the robotic arm, assisted by twin cameras. IIRC some parts of it were designed by a team at Hong Kong Polytechnic University a few km from me, which has worked on Beagle 2 & Chang'e 3.pic.twitter.com/i8RbPPOChq
Getting the sampling working as planned may be more difficult than it seems (ask @NASAInSight's thermal probe or Apollo astronauts etc.), but here comes the hairy part of taking off from the Moon, 1st major launch from a major solar system object since Luna 24 of 1976:pic.twitter.com/lyrV6mbzL6
So after ~2 days of surface operations the ascent stage will have only 1 chance to get to the right rendezvous orbit (15 x 200 km towards the orbiter at 200 km circular per a 2014 paper). Then it has to dock w/ it - never tried robotically that far from Earth.pic.twitter.com/d3f73nYjFR
Those who have read the details of the @NASA/@ESA Mars Sample Return mission plans would probably have a headache on this. Now the Chinese are attempting s/t only slightly easier all by themselves.pic.twitter.com/RJD6CLk0CX
It appears the docking mechanism is some sort of "soft docking" one with claws on the orbiter/return capsule side. The sample container would slide (?) into the return capsule and then automatically sealed. Quite tricky to get that right it seems...pic.twitter.com/HbeGj4C4eh
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