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Chinese rover powers up devices in pioneering moon mission

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Re: Chinese rover powers up devices in pioneering moon mission

#11

Post by justicezyx »

JohnJamesRambo wrote: post #9
SubiculumCode wrote: post #3

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 prin…

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.

That actually would be cool!

Re: Chinese rover powers up devices in pioneering moon mission

#12

Post by JumpCrisscross »

emilfihlman wrote: post #10
JumpCrisscross wrote: post #6

Earlier quoted context omitted.

> 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.)

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 engineer…

> 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

Re: Chinese rover powers up devices in pioneering moon mission

#13

Post by Baeocystin »

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.

Re: Chinese rover powers up devices in pioneering moon mission

#14

Post by TeMPOraL »

JumpCrisscross wrote: post #12
emilfihlman wrote: post #10

Earlier quoted context omitted.

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 engineer…

> 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 fu…

> Spaceflight is expensive. Every watt for a better camera means a watt away from scientific equipment. Power on such missions is micromanaged by necessity.

Also every watt that you can add to the system without taking it away from something else is another watt you need to radiate away after it's done its job. Thermal management is paramount in space missions.

Re: Chinese rover powers up devices in pioneering moon mission

#16

Post by snops »

Baeocystin wrote: post #13

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 wou…

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

Re: Chinese rover powers up devices in pioneering moon mission

#18

Post by superkuh »

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.

Re: Chinese rover powers up devices in pioneering moon mission

#19

Post by craz8 »

snops wrote: post #16
Baeocystin wrote: post #13

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 wou…

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…

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

Re: Chinese rover powers up devices in pioneering moon mission

#20

Post by Theodores »

newnewpdro wrote: post #17

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

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.

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