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Chinese rover powers up devices in pioneering moon mission

87 points by dnetesn 8y ago

sloanedavids 8y ago
It’s strange how they celebrate going to the moon and yet most of their citizens still don’t know about https://en.m.wikipedia.org/wiki/1989_Tiananmen_Square_protests https://en.m.wikipedia.org/wiki/1989_Tiananmen_Square_protes...
SubiculumCode 8y ago
Sloandavids [dead] below, has a point. Celebrating the expansion of knowledge favorable to the Chinese government while censoring the knowledge of how that Chinese government crushed a protest (and a man) with military intervention against its own people, and while China is mass incarcerating whole peoples of non-Chinese ethnicity for 'cultural re-education', is well, totally repugnant, barbaric, and contrary to principles that democratic nations uphold.
- JohnJamesRambo 8y ago
  Just wait until they rove over and find our flag we put there that says “Tiananmen Square Happened” and it flashes on all their TVs. We went for the long game on this one.
  - justicezyx 8y ago
    That actually would be cool!
Entangled 8y ago
I've been combing the web for new pics but have found nothing. Anything new?
Havoc 8y ago
What's with the rubbish photo quality? This is 2019 after all and I'm pretty sure the Chinese know a thing or two about manufacturing cameras.
- JumpCrisscross 8y ago
  > What's with the rubbish photo quality?...I'm pretty sure the Chinese know a thing or two about...cameras The Chinese also know a thing or two about power budgets, bandwidth limitations and optimising between function and vanity. Low quality rover photos show they’re optimising for function, not propaganda value. That’s good. (They’re also awesome pictures.)
  - deleted 8y ago
    [deleted]
  - deleted 8y ago
    [deleted]
  - emilfihlman 8y ago
    Just no. The issue is not power budget, bandwidth or optimisation between function and vanity. Moon has plenty of sunlight, the bandwidth on an Earth-Moon link is very good and there's really no difference between vanity and function in terms of implementation here. The real reasons here are a) the Space Grade™ plague, b) radiation hardening and durability and c) limited value in high quality photos. non-web engineering on big total budget but limited per part projects is very, very conservative.
    - JumpCrisscross 8y ago
      > the bandwidth on an Earth-Moon link is very good The rover is on the far side of the moon. It relies on a single relay satellite at the Earth-Moon L2 [1]. This relay satellite had to be installed specifically for this mission. > Moon has plenty of sunlight Spaceflight is expensive. Every watt for a better camera means a watt away from scientific equipment. Power on such missions is micromanaged by necessity. The functional purpose of the camera is in assisting dis-mounting and post-dismounting inspection. It did that. It also sent home good pictures. [1] https://en.m.wikipedia.org/wiki/Chang%27e_4#Components https://en.m.wikipedia.org/wiki/Chang%27e_4#Components
      - 8y ago
Baeocystin 8y ago
Does anyone know why a halo orbit was chosen for the relay sat instead of a regular, lunar orbit?† I know that due to the moon's lumpy gravitational field, there are only a few stable orbits available, but anything orbiting a Lagrangian point is going to require stationkeeping adjustments regardless, right? †I understand that that would put the lander out of contact during that part of the relay-sat orbit, but it would also completely rule out a major source of potential radio interference during observational periods, which strikes me as an even more important consideration. Data can be stored and batched, after all.
- snops 8y ago
  I think orbiting around L2 would ensure the satellite was at a higher angle in the lunar sky for most of the time, and hence the lander can be in contact for longer, as low angles may be blocked by boulders or crater walls etc. The radio to the satellite would normally use high frequencies so you can have a focused beam for power saving, so it needs to be line of sight. You could transmit faster, but this would take more power. In addition, there is a little rover[1]. NASA rovers since Pathfinder have had some automated driving, I imagine the Chinese can easily do the same, but manually steering is still nice and hence the rover is more useful if you can be in "live" contact with it for longer. [1] https://en.wikipedia.org/wiki/Chang%27e_4#Yutu-2_rover https://en.wikipedia.org/wiki/Chang%27e_4#Yutu-2_rover
  - craz8 8y ago
    The article you linked makes it clear why L2 was chosen - this orbit allows continuous communication between Earth and the lander. If the satellite was at L2, this would not be the case, as the moon would be in the way, so it has to be far enough away to see both the lander location and Earth at the same time Also, orbiting the moon would give you coverage much less than half the time, and you’d need to track the satellite across the sky from the lander
jstanley 8y ago
Where's the best place to go to look at more pictures from this?
newnewpdro 8y ago
The lunar surface is more brown in these photos than the ones from Apollo, which is more accurate?
- Theodores 8y ago
  Your comment reminds me of comments made about the colour of Mars. Allegedly it wasn't red enough and looked too much like Arizona so - allegedly - they made it to the expected red colour and kept this up over a series of missions. This does not answer your question, however, 'white balance' is a thing when it comes to space.
  - newnewpdro 8y ago
    That's funny, but this is a little different since I'm comparing it to the Apollo mission photos. The last thing I expected to see was a brownish lunar surface, considering one of the most notable things about the Apollo photos is their B&W appearance except for the lunar lander and american flag colors. https://www.flickr.com/photos/projectapolloarchive/21037481544/in/gallery-flickr-72157659397648815/ https://www.flickr.com/photos/projectapolloarchive/210374815...
superkuh 8y ago
Just to be clear here because all the press releases are intentionally ambiguous about it: the only serious radio astronomy instruments are the Netherlands-China Low Frequency Explorer (NCLE) package on the relay sat in the L2 halo orbit always in line of sight of Earth. Not the lander, not the rover. The relay sat there is the step towards lunar far side radio astronomy but so far that is not actually going on. It's a cool instrument in that it's antenna are stored as a flat roll but extend out as hollow, rigid tubes.
- dane-pgp 8y ago
  The article says: "Harvard University astronomer Avi Loeb noted, however, that the relay satellite needed to send back information from the far side also contaminates the sky." Does that mean the international community needs to agree a protocol to establish periods of radio silence for objects on the far side of the moon, and for lunar orbiting satellites, so as not to interfere with future radio astronomy instruments?
  - superkuh 8y ago
    I don't think it is that serious yet but hopefully in time we will need to create ITU region 4, https://en.wikipedia.org/wiki/ITU_Region https://en.wikipedia.org/wiki/ITU_Region . The link back to Earth is relatively narrow beam width and it's doubtful a simple dish/feed setup has significant sidebands and even then at only a couple frequencies (probably ~7-8 GHz and ~2 GHz).
daniel_iversen 8y ago
That picture with all the brown dirt totally looks like it was taken on a desert here on earth ;)
- newnewpdro 8y ago
  China faked the landing, it's propaganda. (I'm at least half joking)

87 points by dnetesn 8y ago

It’s strange how they celebrate going to the moon and yet most of their citizens still don’t know about https://en.m.wikipedia.org/wiki/1989_Tiananmen_Square_protests https://en.m.wikipedia.org/wiki/1989_Tiananmen_Square_protes...

SubiculumCode 8y ago

Sloandavids [dead] below, has a point. Celebrating the expansion of knowledge favorable to the Chinese government while censoring the knowledge of how that Chinese government crushed a protest (and a man) with military intervention against its own people, and while China is mass incarcerating whole peoples of non-Chinese ethnicity for 'cultural re-education', is well, totally repugnant, barbaric, and contrary to principles that democratic nations uphold.

JohnJamesRambo 8y ago
Just wait until they rove over and find our flag we put there that says “Tiananmen Square Happened” and it flashes on all their TVs. We went for the long game on this one.
- justicezyx 8y ago
  That actually would be cool!

Entangled 8y ago

I've been combing the web for new pics but have found nothing. Anything new?

Havoc 8y ago

What's with the rubbish photo quality? This is 2019 after all and I'm pretty sure the Chinese know a thing or two about manufacturing cameras.

JumpCrisscross 8y ago
> What's with the rubbish photo quality?...I'm pretty sure the Chinese know a thing or two about...cameras The Chinese also know a thing or two about power budgets, bandwidth limitations and optimising between function and vanity. Low quality rover photos show they’re optimising for function, not propaganda value. That’s good. (They’re also awesome pictures.)
- deleted 8y ago
  [deleted]
- deleted 8y ago
  [deleted]
- emilfihlman 8y ago
  Just no. The issue is not power budget, bandwidth or optimisation between function and vanity. Moon has plenty of sunlight, the bandwidth on an Earth-Moon link is very good and there's really no difference between vanity and function in terms of implementation here. The real reasons here are a) the Space Grade™ plague, b) radiation hardening and durability and c) limited value in high quality photos. non-web engineering on big total budget but limited per part projects is very, very conservative.
  - JumpCrisscross 8y ago
    > the bandwidth on an Earth-Moon link is very good The rover is on the far side of the moon. It relies on a single relay satellite at the Earth-Moon L2 [1]. This relay satellite had to be installed specifically for this mission. > Moon has plenty of sunlight Spaceflight is expensive. Every watt for a better camera means a watt away from scientific equipment. Power on such missions is micromanaged by necessity. The functional purpose of the camera is in assisting dis-mounting and post-dismounting inspection. It did that. It also sent home good pictures. [1] https://en.m.wikipedia.org/wiki/Chang%27e_4#Components https://en.m.wikipedia.org/wiki/Chang%27e_4#Components
    - 8y ago

Baeocystin 8y ago

Does anyone know why a halo orbit was chosen for the relay sat instead of a regular, lunar orbit?† I know that due to the moon's lumpy gravitational field, there are only a few stable orbits available, but anything orbiting a Lagrangian point is going to require stationkeeping adjustments regardless, right? †I understand that that would put the lander out of contact during that part of the relay-sat orbit, but it would also completely rule out a major source of potential radio interference during observational periods, which strikes me as an even more important consideration. Data can be stored and batched, after all.

snops 8y ago
I think orbiting around L2 would ensure the satellite was at a higher angle in the lunar sky for most of the time, and hence the lander can be in contact for longer, as low angles may be blocked by boulders or crater walls etc. The radio to the satellite would normally use high frequencies so you can have a focused beam for power saving, so it needs to be line of sight. You could transmit faster, but this would take more power. In addition, there is a little rover[1]. NASA rovers since Pathfinder have had some automated driving, I imagine the Chinese can easily do the same, but manually steering is still nice and hence the rover is more useful if you can be in "live" contact with it for longer. [1] https://en.wikipedia.org/wiki/Chang%27e_4#Yutu-2_rover https://en.wikipedia.org/wiki/Chang%27e_4#Yutu-2_rover
- craz8 8y ago
  The article you linked makes it clear why L2 was chosen - this orbit allows continuous communication between Earth and the lander. If the satellite was at L2, this would not be the case, as the moon would be in the way, so it has to be far enough away to see both the lander location and Earth at the same time Also, orbiting the moon would give you coverage much less than half the time, and you’d need to track the satellite across the sky from the lander

jstanley 8y ago

Where's the best place to go to look at more pictures from this?

newnewpdro 8y ago

The lunar surface is more brown in these photos than the ones from Apollo, which is more accurate?

Theodores 8y ago
Your comment reminds me of comments made about the colour of Mars. Allegedly it wasn't red enough and looked too much like Arizona so - allegedly - they made it to the expected red colour and kept this up over a series of missions. This does not answer your question, however, 'white balance' is a thing when it comes to space.
- newnewpdro 8y ago
  That's funny, but this is a little different since I'm comparing it to the Apollo mission photos. The last thing I expected to see was a brownish lunar surface, considering one of the most notable things about the Apollo photos is their B&W appearance except for the lunar lander and american flag colors. https://www.flickr.com/photos/projectapolloarchive/21037481544/in/gallery-flickr-72157659397648815/ https://www.flickr.com/photos/projectapolloarchive/210374815...

superkuh 8y ago

Just to be clear here because all the press releases are intentionally ambiguous about it: the only serious radio astronomy instruments are the Netherlands-China Low Frequency Explorer (NCLE) package on the relay sat in the L2 halo orbit always in line of sight of Earth. Not the lander, not the rover. The relay sat there is the step towards lunar far side radio astronomy but so far that is not actually going on. It's a cool instrument in that it's antenna are stored as a flat roll but extend out as hollow, rigid tubes.

dane-pgp 8y ago
The article says: "Harvard University astronomer Avi Loeb noted, however, that the relay satellite needed to send back information from the far side also contaminates the sky." Does that mean the international community needs to agree a protocol to establish periods of radio silence for objects on the far side of the moon, and for lunar orbiting satellites, so as not to interfere with future radio astronomy instruments?
- superkuh 8y ago
  I don't think it is that serious yet but hopefully in time we will need to create ITU region 4, https://en.wikipedia.org/wiki/ITU_Region https://en.wikipedia.org/wiki/ITU_Region . The link back to Earth is relatively narrow beam width and it's doubtful a simple dish/feed setup has significant sidebands and even then at only a couple frequencies (probably ~7-8 GHz and ~2 GHz).

daniel_iversen 8y ago

That picture with all the brown dirt totally looks like it was taken on a desert here on earth ;)

newnewpdro 8y ago
China faked the landing, it's propaganda. (I'm at least half joking)