China’s Chang’e-3 and Jade Rabbit duo land on the Moon

by Rui C. Barbosa

China’s Chang’e-3 and the lunar rover Yutu (Jade Rabbit) have landed on the lunar surface at 1:11 pm UTC on Saturday. The duo were launched by a Long March 3B on December 1, which was followed by a nominal flight into lunar orbit and subsequently China’s first soft landing on the Moon.

China’s Mission to the Moon:

The Chinese duo have enjoyed a trouble-free flight towards the Moon, with the spacecraft entering a reported 210.3 x 389109.2 km x 28.5 deg orbit during the week.

As many as three orbital corrections were understood to be required, with the first taking place at 07:50 UTC on December 2, followed by a second at 08:20 UTC on December 3.

While the Chinese didn’t report information about the second burn, it is understood a third was not required.

Z8After entering a 100 km lunar orbit on December 6, Chang’e-3 began to prepare its systems for the most important phase of the mission – the landing. On December 10, the probe executed a burn of its main engine to lower its altitude above the lunar surface.

Upon entering lunar orbit, Chang’e-3 underwent six stages of deceleration to descend from 15 km above to the lunar surface using a variable thrust engine.

During the descent the attitude of the probe was controlled using 28 small thrusters.

Z99Following deceleration, the vehicle quickly adjusted its attitude, approaching the lunar surface. During this phase the instruments analyzed the planned descent area.

The main engine automatically shutdown at an altitude of four meters, allowing the rover to free fall on the surface.

The landing sequence was executed perfectly, resulting in the vehicle selecting its preferred landing spot almost immediately, even landing without delay, technically 30 minutes ahead of schedule.

After the soft landing, Chang’e-3 charged and initialized the Yutu rover that soon began to communicate with mission control. After communications were established, Yutu unlocked the docking mechanism and then drove to the ladder transfer mechanism.

Z88The transfer mechanism then descended to the surface of the moon, and moved away from Chang’e-3.

Some nine hours after the separation, the Chang’e-3 and Yutu began to capture some photographs of each other using the onboard cameras.

The lander is equipped with a radioisotope thermoelectric generator (RTG) to power the lunar operations during the three-month mission. The energy will be used to power the scientific payload of seven instruments and cameras.

The Chang’e-3 lander also carries four instruments: the MastCam, the Descent Camera, the Lunar-based Ultraviolet Telescope (LUT) and the Extreme Ultraviolet Imager (EUV).

*Click here for additional specifics in the instrumentation*

Z3Yutu is equipped with a solar panel to power the vehicle during the lunar day on a three month mission. During this time, Yutu will explore a three square kilometer area, travelling a maximum distance of 10 km from the landing point.

The rover will be capable of real time video transmission, while it will be able to dig and perform simple analysis of soil samples. For the real time video transmissions Yutu will use the PanCam. These cameras will provide stereo images in high-resolution and will eventually give three-dimensional imaging for the scientists on Earth.

It total, the Yuti rover carries four instruments: the PanCam; the Ground Penetration Radar (GPR); the VIS/NIR Imaging Spectrometer (VNIS); and the Alpha Particle X-Ray Spectrometer (APXS).

Z11Located on the top mast of Yutu, the PanCam will acquire 3D imagery of the lunar surface for surveying the terrain, geological features and structures, and craters inside the target region. It will also monitor the operational state of the lander.

Lying inside the rover, the Ground Penetration Radar will measure lunar soil depth and structural distribution of soil, magma, lava tubes and sub-surface rock layers.

This was the first lunar landing since Luna-24 launched on August 9, 1976. That mission touched down on the surface of the moon on August 18 of that year, ahead of a soil retrieving mission that returned to Earth six days later.

(Images via China’s CCTV).

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