China's Space Program News Thread

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plawolf

plawolf

Lieutenant General
t2contra said:
China's Chang'e-3 makes successful Moon landing

By Brian Dodson

December 14, 2013

Following 12 minutes of precise maneuvering which began in lunar orbit, China's Chang'e-3 lunar lander, with the Yu Tu (Jade Rabbit) lunar rover onboard, successfully landed on the Moon's surface at 13:11 UT Saturday night. At this point, Chang'e-3's solar panels were opened to begin charging the rover's batteries for its first drive about the lunar surface, which is expected to begin about seven hours after landing.

Chang'e-3 began its descent from the lowest part of its orbit, some 15 km (9 miles) above the Moon's surface. During its descent to an altitude of 2 km (1.2 mi), deceleration reduced the 1.71 km/s (1.06 mi/s) orbital velocity of the Chang'e-3 to zero. At 2 km altitude, the automatic landing sequence cut in, setting Chang'e-3 on course for its landing in Sinus Iridum (Sea of Rainbows) without further control from Earth.

At an altitude of 100 meters (330 ft), the Chang'e-3 began to hover over the surface, building a map of ground conditions and landing obstacles. Hovering was planned to last up to 100 seconds, but actually only took about 20 seconds.

A brief pause was taken at an altitude of 30 meters to further refine the approach. Once the landing site was chosen autonomously, Chang'e-3 slows edged down to an altitude of 4 meters, at which point the rocket was cut off, and the lander fell the rest of the way, landing on the surface with impact-absorbing legs.

China Central Television has now reported that the lander has deployed its solar panels, and has established X-band telemetry with Earth. The Jade Rabbit rover is being charged and initialized before it will be unlocked from its storage configuration during the flight. The rover will then establish its own separate data link with Earth, deploy its mast and panels, and moves onto its unloader, which lowers YuTu to the lunar surface, a process that will take several hours. At this point both the lander and rover will take panoramic images of their immediate surroundings before the rover begins local exploration.

Congratulations, China! It is about time someone went back to the Moon, and you did it in style. This video shows the soft landing from orbit to ground.
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Amazing news, but why wasn't the batteries fully charged when Yutu was launched?
 
plawolf

plawolf

Lieutenant General
vesicles said:
Moon dirt is different from the earth dirt. Moon dirt is much more reflective, thus causing objects to be much brighter on the moon even though there is little light.
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Lack of an atmosphere means no light is reflected or absorbed before it hits the lunar surface compared to earth, making everything seem brighter.
 
Quickie

Quickie

Colonel
vesicles said:
Moon dirt is different from the earth dirt. Moon dirt is much more reflective, thus causing objects to be much brighter on the moon even though there is little light.
Click to expand...

The moon's surface has about the same albedo, 0.04 to 0.12, as asphalt. i.e. very low reflectivity. Sunlight reaching the moon surface is much more intense than that on earth because the moon don't have an atmosphere to reflect the sun's radiation. The lack of diffuse lights due to the lack of atmosphere means that everything on the moon looks to be in high contrast. Notice how bright the Yutu rover is, compared to the moon surface.
 
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chuck731

Banned Idiot
vesicles said:
Moon dirt is different from the earth dirt. Moon dirt is much more reflective, thus causing objects to be much brighter on the moon even though there is little light.
Click to expand...

Uh, no. Moon dirt on average is only a little more reflective than coal dust. If you ever walked on a fresh basalt lava flow on earth, like you would find in Hawaii or Iceland, you would be walking on something about as dark as most if the lunar lowlands on the near side, where Yutu landed.

Moon overall is quite a low albedo object. It may look bright in dark sky, when everything around it is nearly black, but the moon is in direct sunlight. But if you have an object of ordinary reflectivity, say similar to photographic gray card, or similar to reflectivity of the earth seen from space, next to the moon under the same sunlight, the moon would look very dark indeed by comparison, practically like a black bolling ball.

This is why the Yutu rover looks washed out in the photo. In order to make the lunar surface appear brighter than black gray, cameras with ordinary dynamic range will have to greatly overexpose objects with light paint and bare gold foil reflectivity.
 
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