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  China's Chang'e 4: Questions and comments

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Author Topic:   China's Chang'e 4: Questions and comments
Robert Pearlman
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posted 12-07-2018 06:15 AM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
Please use this topic to discuss China's Chang'e 4 mission to send a probe and rover to make the first-ever landing on the far side of the moon.

Robert Pearlman
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posted 12-07-2018 06:18 AM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
Launch of the Long March 3B rocket with the Chang'e 4 lander and rover is expected between 1:15 and 1:34 p.m. EST (18:15 to 18:34 GMT) on Friday (Dec. 7). Per Andrew Jones writing for gbtimes:
Unfortunately it looks unlikely that China will be providing live coverage of the launch, in which case the first official news after liftoff may only come once the spacecraft have successfully entered lunar transfer orbit.
If all goes to plan, the lander and rover are expected to touch down within the South Pole-Aitken Basin on our about Jan. 3, 2019, after a five-day trip to the moon and three weeks spent in lunar orbit.

Robert Pearlman
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posted 12-07-2018 06:07 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
The Chang'e 4 mission lifted off Friday (Dec. 7) at 1:23 p.m. EST (1823 GMT or 2:23 a.m. Beijing time on Dec. 8) on a Long March 3B rocket from the Xichang Satellite Launch Center in southwest China.

Grounded!
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posted 12-07-2018 06:19 PM     Click Here to See the Profile for Grounded!   Click Here to Email Grounded!     Edit/Delete Message   Reply w/Quote
The lander and rover kind of remind me of the Apollo years.

Blackarrow
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posted 12-07-2018 08:26 PM     Click Here to See the Profile for Blackarrow     Edit/Delete Message   Reply w/Quote
I assume Dr Schmitt will be watching with interest.

Philip
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posted 01-03-2019 03:14 AM     Click Here to See the Profile for Philip   Click Here to Email Philip     Edit/Delete Message   Reply w/Quote
A Chinese robotic probe carrying a small, multi-wheeled rover has become the first spacecraft in history to land on the far side of the moon.
Great to see China's successful efforts to explore Earth's natural satellite. Can't wait to see Taikonauts on the moon in my lifetime!

denali414
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posted 01-03-2019 06:55 AM     Click Here to See the Profile for denali414   Click Here to Email denali414     Edit/Delete Message   Reply w/Quote
Great achievement for China!. Really heading into a second "golden age of space exploration" with all that is going on with USA, China, Russia, ESA and the commercial companies like SpaceX, Boeing, Virgin, etc.

Solarplexus
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posted 01-03-2019 07:55 AM     Click Here to See the Profile for Solarplexus     Edit/Delete Message   Reply w/Quote
Congratulation. Maybe we get a female Taikonaut as the first woman on another planet.

Jurg Bolli
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posted 01-03-2019 08:27 AM     Click Here to See the Profile for Jurg Bolli   Click Here to Email Jurg Bolli     Edit/Delete Message   Reply w/Quote
This is a great achievement, congratulations.

Robert Pearlman
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posted 01-03-2019 09:26 AM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
The Change'4 rover, now officially named Yutu 2 ("Jade Rabbit 2"), has rolled off the lander onto the surface of the moon.

David C
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posted 01-03-2019 11:31 AM     Click Here to See the Profile for David C     Edit/Delete Message   Reply w/Quote
Well done China.

Scott
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posted 01-03-2019 12:00 PM     Click Here to See the Profile for Scott   Click Here to Email Scott     Edit/Delete Message   Reply w/Quote
The first surface images from the far side of the Moon. Wow. Truly amazing technical accomplishment.

Robert Pearlman
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posted 01-04-2019 09:46 AM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
From CGTN:
"What's next for the rover is to take a picture of the front side of the lander, after that, it will go to its planned area and start a series of scientific exploration projects in the Von Karman crater," said Zhang Yuhua, deputy chief commander and designer for the Chang'e-4 lunar mission.

The Jade Rabbit-2 will survey the lunar terrain during the Moon's daytime which lasts until January 12. After that, a 14-day-long Moon night is expected to come.

Per the China National Space Administration, rover activities are being halted through Jan. 10 to avoid overheating ("a noon break").

Blackarrow
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posted 01-04-2019 10:47 AM     Click Here to See the Profile for Blackarrow     Edit/Delete Message   Reply w/Quote
A great achievement, but I can't help thinking back 48 years to Lunokhod 1. Did the Russians ever consider a far-side Lunokhod with a relay satellite?

Robert Pearlman
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posted 01-04-2019 01:14 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
From Asif Siddiqi's "Challenge to Apollo":
One of [Chief Designer at the Lavochkin Design Bureau Georgi] Babakin's final dreams had been to recover soil samples from the far side of the Moon. Work on such a project had, in fact, begun in 1970 during his lifetime. The plan consisted of an orbiter and a lander — the former to serve as a communications satellite between the latter and Earth. The mission was evidently scheduled for launch sometime in 1972, but after Babakin's death, the idea gradually fell to the wayside, partially because of the high level of technical complexity.

Blackarrow
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posted 01-04-2019 08:32 PM     Click Here to See the Profile for Blackarrow     Edit/Delete Message   Reply w/Quote
So that would have been more of a Luna 16-type mission than a Lunokhod.

It's not the only plan that didn't come to fruition until much later. I distinctly remember a TV news report in (probably) the late 1970s telling me how NASA planned to collect a sample from an asteroid and return it to Earth. I thought at the time that the plan seemed over-ambitious. Forty years (or so) later, we are watching as preparations are made for OSIRIS-REx to bring a sample of asteroid Bennu back to Earth.

All things come to him who waits...

Blackarrow
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posted 01-09-2019 07:53 AM     Click Here to See the Profile for Blackarrow     Edit/Delete Message   Reply w/Quote
"What's next for the rover is to take a picture of the front side of the lander...
Should we be surprised that no picture (or at least none that I can find) of the lander has been published yet? The mission plan clearly intended for the image to be taken before Yutu 2's mid-day "siesta."

Robert Pearlman
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posted 01-09-2019 09:20 AM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
Per Chinese media reports, the photo of the lander is planned for after Yutu 2's nap.

Robert Pearlman
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posted 01-10-2019 09:47 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
China's Chang'e 4 lander took panoramic photos on the lunar surface:

Robert Pearlman
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posted 01-11-2019 09:13 AM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
The Chang'e 4 lander and Yutu 2 rover on the surface of the moon:

Real time footage of the Change'e 4 lander's descent to the surface:

Blackarrow
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posted 01-11-2019 11:27 AM     Click Here to See the Profile for Blackarrow     Edit/Delete Message   Reply w/Quote
Fascinating.

Kite
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posted 01-11-2019 01:18 PM     Click Here to See the Profile for Kite     Edit/Delete Message   Reply w/Quote
Certainly is. Takes one back to the manned landings.

Rick Mulheirn
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posted 01-11-2019 01:40 PM     Click Here to See the Profile for Rick Mulheirn   Click Here to Email Rick Mulheirn     Edit/Delete Message   Reply w/Quote
The images of the lunar surface show in general a very familiar appearance. No crater under the lander despite footage clearly showing the impact of the descent engine on the regolith. Theses images serve only to remind folks that Man did land on the moon 50 years ago.

Robert Pearlman
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posted 01-12-2019 10:16 AM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
NASA/Arizona State University release
Chang'e 4 Lander Coordinates

Chang'e 4 safely set down on the plains of Von Kármán crater last week (3 January 2019). Soon thereafter a color image of the immediate surroundings was relayed back to the Earth from the farside!

Above: Following the Chang'e 4 descent frames (CNSA/CLEP) to the surface makes it easy to find the exact landing spot in a NAC image, which was taken before the landing. Note that the NAC image is rotated so north is down to match the Chang'e 4 frames. NAC M1298916428LR. (NASA/GSFC/Arizona State University)

The prominent crater (about 25 meter diameter) in front of the lander can be seen just below and to the left of the bottom arrow (below).

Above: The Chang'e 4 spacecraft set down between the two arrows at 45.457 degrees South, 177.589 degrees East, plus or minus 20 meters. Full resolution (80 cm pixel scale) NAC image M1298916428LR, acquired on 8 December 2018 (before the landing), note that image is rotated 180 degrees relative to the opening images, north is up. Image width is 880 meters. (NASA/GSFC/Arizona State University)

Explore more of the area around the landing site; same image as above, but more of it (80 cm pixels) here.

Robert Pearlman
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posted 01-12-2019 10:21 AM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
And from Jonathan McDowell on Twitter:
Here is where Chang'e-4 landed, on a map of the farside:

And a closeup with crater names:

Robert Pearlman
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posted 01-15-2019 09:37 AM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
Cotton seeds inside a mini biosphere on the Chang'e 4 lander have sprouted.
Chinese media state that the experiment contains six species: cotton, rapeseed, potato, arabidopsis, fruit fly and yeast, with Xinhua reporting that no signs of growth have been found among the species other than cotton.

Xie Gengxin, chief designer of the biological experiment payload for the Chang'e-4 mission, told CCTV that, "There are animal, plants and microorganisms in this payload, creating a micro-ecosystem in a closed environment. We guide the sunlight to the inside of the tin, which is much stronger than that on the Earth. We will study their photosynthesis under strong sunlight and compare it with the experiment on the Earth."

Xie added that the experiment is taking place in the low gravity and high radiation lunar environment.

Blackarrow
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posted 02-02-2019 08:22 AM     Click Here to See the Profile for Blackarrow     Edit/Delete Message   Reply w/Quote
It's good to see that both lander and rover "woke up" last Wednesday after lunar farside dawn. Apparently they encountered lower temperatures (minus 190 deg. C) than expected.

Robert Pearlman
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posted 02-02-2019 11:07 AM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
From Andrew Jones (via Twitter, via Weibo):
Here's a new image of the Chang'e 4 lander taken by Yutu 2 rover. One of the three 5-metre booms for the low frequency radio astronomy instrument can be clearly seen rising vertically from the lander.

Looks like the image was taken at the point at which Yutu 2 spent the first lunar night, based on this map of Yutu-2 route relative to the lander. The LFS instrument is also not entirely dissimilar to the low-frequency astronomy NCLE on the Queqiao relay satellite.

Robert Pearlman
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posted 02-06-2019 01:02 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
NASA/Arizona State University release
First Look: Chang'e 4

On 3 January 2019 the Chinese spacecraft Chang'e 4 safely landed on the floor of Von Kármán crater (186 kilometer diameter, 116 miles). Four weeks later (30 January 2019), as LRO approached the crater from the east, it rolled 70 degrees to the west to snap this spectacular view looking across the floor towards the west wall.

Because LRO was 330 kilometers (205 miles) to the east of the landing site, the Chang'e 4 lander is only about two pixels across (bright spot between the two arrows), and the small rover is not detectable. The massive mountain range in the background is the west wall of Von Kármán crater, rising more than 3000 meters (9850 feet) above the floor.

Above: Arrows indicate position of Chang'e 4 lander on the floor of Von Kármán crater. The sharp crater behind and to the left of the landing site is 3900 meters across (12,800 feet) and 600 meters (1970 feet) deep. Image was shrunk by more than a factor of ten (full resolutiuon available here). (NASA/GSFC/Arizona State University)

Above: Area around lander enlarged by a factor of two relative to the native pixel scale (see zoomify below), bright speck between two arrows is the lander. The large crater in the center (just right and below arrows) is about 440 meters (1440 feet) across. (NASA/GSFC/Arizona State University)

Robert Pearlman
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posted 02-08-2019 04:59 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
NASA/Arizona State University release
Chang'e 4 Rover Comes into View

On 30 January LROC acquired a spectacular limb shot centered on the Chang'e 4 landing site, looking across the floor of Von Kármán crater. At the time, LRO was more than 200 kilometers from the landing site so Chang'e 4 was only a few pixels across and the rover was not discernable. The following day LRO was closer to the site and again slewed (59 degrees this time) to capture another view.

This time the small Yutu-2 rover shows up (two pixels) just north of the lander. Also, shadows cast by the lander and rover are now visible.

Above: The Chang'e 4 rover is now visible to LROC! Just beyond the tip of the right arrow is the rover and the lander is to the right of the tip of the left arrow. The image appears blocky because it is enlarged 4x to make it easier to see the two vehicles. North is to the upper right. (NASA/GSFC/Arizona State University)

At some time after the formation of Von Kármán crater, the crater floor was covered by eruptions of basaltic lava, similar to the eruptions in Hawaii last summer. Chang'e 4 will collect compositional measurements of these farside basaltic rocks, and lunar scientists are anxiously awaiting these results. Do volcanic rocks on the farside differ from the basalts collected from the nearside? We will have to wait and see!

A striking aspect of the floor of Von Kármán crater is the number and variety of impact craters. There is a high density of craters because the surface is more than 3 billion years old! During those 3 billion years, so many small craters (<200 meters (660 feet) in diameter) formed that when a new one forms, the total number of craters does not increase. This seemingly counterintuitive situation occurs because each new crater erases, on average, one older crater of comparable size, a state known as "equilibrium" to crater counting geologists. For surfaces this old (in equilibrium), only larger craters (>1000 meters (3280 feet) diameter), which are not in equilibrium, continue to increase in density and can be used to estimate the age of the surface.

Note also all of the small craters that have formed on top of larger ones. Smaller impacts wear down and degrade larger craters over time. You can easily see a wide variety of crater degradation states, ranging from sharp and crisp (new) to highly degraded (old). As result of all of these impacts (small and large), the surface of the Moon consists of a very fine powder known as regolith, in which the Apollo astronauts made their distinct boot prints. Explore the variety of craters across the floor of Von Kármán crater in the full NAC image.

Above: Chang'e 4 lander (near tip of left arrow) and rover (near tip of right arrow) nestled among craters on the floor of Von Kármán crater. Image is 1700 meters (5580 feet) wide across the center. (NASA/GSFC/Arizona State University)

Robert Pearlman
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posted 02-15-2019 08:52 AM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
International Astronomical Union (IAU) release
IAU Names Landing Site of Chinese Chang'e-4 Probe on Far Side of Moon

Five sites on the far side of the Moon now have official names, including Chang'e-4's landing site. The names have significance in Chinese culture, reflecting the background of the probe's team.

The IAU Working Group for Planetary System Nomenclature has approved the name Statio Tianhe for the landing site where the Chinese spacecraft Chang'e-4 touched down on 3 January this year, in the first-ever landing on the far side of the Moon. The name Tianhe originates from the ancient Chinese name for the Milky Way, which was the sky river that separated Niulang and Zhinyu in the folk tale "The Cowherd and the Weaver Girl."

Four other names for features near the landing site have also been approved. In keeping with the theme of the above-mentioned folk tale, three small craters that form a triangle around the landing site have been named Zhinyu, Hegu, and Tianjin, which correspond to characters in the tale. They are also names of ancient Chinese constellations from the time of the Han dynasty. The fifth approved name is Mons Tai, assigned to the central peak of the crater Von Kármán, in which the landing occurred. Mons Tai is named for Mount Tai, a mountain in Shandong, China, and is about 46 km to the northwest of the Chang'e-4 landing site.

SkyMan1958
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posted 02-15-2019 05:59 PM     Click Here to See the Profile for SkyMan1958   Click Here to Email SkyMan1958     Edit/Delete Message   Reply w/Quote
It's amazing to me how quickly the Chinese were able to get the IAU to name the features, given how long it took the IAU to accept some, but even now not all, of the names the Apollo astronauts used for the approaches to their landing sites, and at the sites themselves.

The cynic in me wonders if the non-acceptance of Apollo names was a function of anti-American sentiment, or the quick acceptance of the Chinese names was perhaps speeded along by the greasing of some palms under the table by a Chinese government that is more accepting of the ways of the world.

Robert Pearlman
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posted 02-15-2019 06:06 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
Apollo was a different era. There were reportedly objections raised by the Soviet Union over some of the Apollo names.

SkyMan1958
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posted 02-15-2019 08:33 PM     Click Here to See the Profile for SkyMan1958   Click Here to Email SkyMan1958     Edit/Delete Message   Reply w/Quote
Just for interests sake, do you know if the US in the early 1960's had questioned the naming of assorted lunar features on the far side of the Moon? Obviously the biggest features were all given Russian/Soviet names as they were the first to image the far side.

Clearly the US when Mariner 4 and succeeding Mariners flew by Mars (not to mention Mariner 9 orbiting Mars), gave fairly "universal" names to the imaged features.

Robert Pearlman
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posted 02-15-2019 09:41 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
I don't know the details, but Wikipedia notes the Soviet-assigned names weren't universally accepted:
As many prominent landscape features of the far side were discovered by Soviet space probes, Soviet scientists selected names for them. This caused some controversy, and the International Astronomical Union, leaving many of those names intact, later assumed the role of naming lunar features on this hemisphere.

Headshot
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posted 02-16-2019 01:31 PM     Click Here to See the Profile for Headshot   Click Here to Email Headshot     Edit/Delete Message   Reply w/Quote
The evolution of applying names to lunar features, in a consistent manner, is long and torturous at best; even without taking nationalistic pressures into account. Appropriate conventions were not formalized and accepted by the IAU until long after Apollo stopped flying. By far the best account is given in Mapping and Naming the Moon by Ewen A. Whitaker.

Robert Pearlman
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posted 03-06-2019 12:09 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
China’s Yutu-2 rover is continuing to make tracks on the lunar far side and has returned new images of rocks in its path inside Von Kármán crater, while the lander and rover continue with their science objectives, Andrew Jones reports for The Planetary Society.
Yutu-2 awakened for lunar day 3 of the mission at 02:51 UTC on 28 February, with the lander following later the same day at 23:52. A few days later, the rover stood down for its ‘noon nap’ to avoid heating issues from a high solar incidence angle, at 10:25 UTC on March 3. It will resume its activities early on 10 March, before entering a sleep state around 02:00 UTC on 13 March, when the Sun is low in the sky over Von Kármán crater in preparation for the lunar nighttime.

According to a release by the China Lunar Exploration Program (CLEP) on 4 March, Yutu-2 has so far travelled 127 meters, adding 7 meters to the total of 120 meters driven on lunar days 1 (44.185 m) and 2 (75.815 m).

The apparent relatively low distance is believed to be due to Yutu-2 taking time to image nearby rocks and features in the regolith.

All times are CT (US)

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