Chinese Lunar Probe Lands Successfully

China's Chang'e 3 moon probe made its intended landing earlier today, setting down softly in the moon's Sinus Iridum, as reported by Reuters. From the article: "The Chang'e 3, a probe named after a lunar goddess in traditional Chinese mythology, is carrying the solar-powered Yutu, or Jade Rabbit buggy, which will dig and conduct geological surveys. ... China Central Television (CCTV) broadcast images of the probe's location on Saturday and a computer generated image of the probe on the surface of the moon on its website. The probe and the rover are expected to photograph each other tomorrow. ... The Bay of Rainbows was selected because it has yet to be studied, has ample sunlight and is convenient for remote communications with Earth, Xinhua said. The rover will be remotely controlled by Chinese control centers with support from a network of tracking and transmission stations around the world operated by the European Space Agency (ESA)."

Comments

First

[Dan East]

In case anyone cares, the first soft moon landing was on January 31, 1966 by the Soviet lander Lana-9. It still boggles my mind how they were able to achieve that without anything remotely resembling a modern computing device.

Re:First

[fisted]

Sorry to break it to you but they did have turing-complete machines in '66, which do more than ``remotely resemble'' modern computing devices, as the fundamental principles didn't change.

Re:First

[Trepidity]

Nitpick: the name is Luna-9.

The first landing of any kind (a crash landing), was the Soviet Luna-2 in 1959. The U.S. then sent a series of crash-impact spacecraft in the early 1960s, the Ranger series, whose goal was to take photos during the final descent, along with testing out systems. Five of the nine Ranger missions successfully impacted the moon, and three of them managed to send back photos.

Then as you note, Luna-9 was the first non-crash landing, in 1966.

Re:First

[Dan East]

Are you saying that Luna-9 was controlled by a Turing-complete computer? From what I can discover it only had a programmable timing device, which would trigger a fixed list of tasks after variable delays. Stuff like shutting off the main engines was done by a physical switch that detected when the lander was just above the surface. I stand by my comment that it was not controlled by anything remotely resembling a modern computer.

Re:First

[Trepidity]

Two of them actually did miss, and are now orbiting the sun in deep space. The other two didn't get far enough to miss.

Ranger 1 and 2 were botched launches, which barely made it into space into unstable low-earth orbits, from which they burned up on reentry shortly thereafter.

Ranger 3 did in fact miss the moon. It successfully launched to high-earth orbit, and then successfully boosted out of high-earth orbit towards the moon. But not quite towards the moon enough. It missed the moon by 22,000 miles and flew past it into deep space.

Ranger 4 was the first successful mission. And then Ranger 5 missed again, this time by a much smaller amount, only 450 miles. The exit from high-earth orbit towards the moon appears to have been reasonably good this time, and any minor trajectory errors were supposed to be fixed in a mid-course corrective burn. But the craft lost power after exiting earth orbit, so was unable to make the mid-course correction, causing it to miss.

More info in the usual place.

Re:First

[DerekLyons]

Luna 9 did not have a computer. It was all careful launch timing and Newtonian mechanics to ensure it got where it needed to be and deployed what it needed to precisely when it needed to. The closest thing it had to a computer was a clock that made these things happen at precise intervals.

A certain amount of luck was involved too... a couple of feet more per second error, and that timer (pre-programmed on the ground before flight) could have been hopelessly out of sync with what was actually happening.
 

If the whole thing weighed 220 lbs., where would you even fit a meaningful 1966 computer?

SLBM guidance computers of the era weighed in at around forty to sixty pounds. Gemini's onboard guidance computer tipped the scales at a hair under sixty pounds. The Apollo guidance computer (directly descend from an SLBM system) weighed seventy pounds.
 
Not that they had one, or the Soviets were that advanced of course, but not all meaningful computers available in the sixties were room sized behemoths weighing tons.

Re:They have the money to do this

[ArbitraryName]

China has no debt? Really? China is no paragon of fiscal virtue, they're barreling down the road to financial ruin unless they do some significant restructuring.

Re:If the mission failed ...

[gerddie]

If the mission failed, would they admit it, or release some photos anyway? (Could they get away with it?)

No, because ESA helps during the whole mission.

Re:Kicking up the lundar dust

[AJWM]

Dust? Seriously?

This is high vacuum we're talking about. Lunar dust is just tiny rocks, they get kicked up and immediately fall back to the surface. It's not as though the dust is going to float for days (or even minutes) in the (virtually non-existent) lunar atmosphere. (Sure sign of badly written SF or shot-in-a-studio movie footage: dust on the real Moon doesn't cloud, it sprays then drops.)

Sure, the exhaust plume gases will stick around for a bit. That will give LADEE something to help calibrate its instruments against, since presumably the reaction products are known.

Re: Kicking up the lundar dust

[AJWM]

While the Outer Space Treaty has some things to say about it (the Moon Treaty was never ratified, or even signed by many of the players), historically the rules of precedence for establishing claim over new lands has been:
1. First to spot it.
2. First to plant a flag on it (which historically implied setting foot)
3. First to set up a base or fort on it
4. First to establish a settlement (ie, permanent habitation) on it.

With "right of ownership" proceeding in the above order. Robotic flag planting as we've had since the mid 1960's might be step 1.5, which is where China is at. USA was at 3 for a brief time in 1969-72 (since the later Apollo missions had surface stays of several days) although disclaimed it with the "we came in peace for all mankind" verbiage on the landing plaques.

If/when China establishes a manned base on the Moon, is there going to be anyone in a position to argue about it (beyond stern words at the UN and threats to remove "Most Favored Nation" trading status) if they claim ownership?

Re:If the mission failed ...

[ihtoit]

(...Could other governments or amateurs with telescopes see for themselves?)

No, because the probe is just too damn small.

None of them can see it. The probe (or to borrow another local example, the Apollo 11 flag) is far too small to be seen with any telescope on Earth, or even the Hubble space telescope (which is in low Earth orbit).

The Lunar Reconnaissance Orbiter (orbiting the Moon) took pictures of the Apollo 11 landing site, however. It showed a long shadow cast by the lower lander stage, but not the stage itself - again, it's just too small.

You can approximate the angular size of an object by dividing its width by its distance from the telescope:

A galaxy might be around 100,000 light years in diameter. At a distance of ten billion light years, it would have an angular size of:
(100,000 light years) / (10,000,000,000 light years) = 0.00001 radians. HST can (and has) taken images containing *millions* of these galaxies.

Now we do the same for a flag on the Moon, generously estimated as 1 metre in width:
(1 metre) / (384,400,000 meters) = 0.0000000026 radians

Well, look at that. Seeing the flag requires about 3800 times the resolving power needed to see the galaxy. Who would have guessed?

This is something that *cannot* be done optically. The wavelength of visible light is just too long. By about 3800 times the wavelength needed. Now we're in high-energy cosmic ray (X-Ray in the Gigawatts) range.