Chang’e-3: Chinese lunar rover heading to the Moon

by Rui C. Barbosa

The Chinese have begun their most ambitious lunar mission to date, following the successful launch their Long March 3B rocket carrying the Chang’e-3 probe and Yutu lunar rover. Launch was on schedule at 17:30 UTC on Sunday, taking place from the LC2 Launch Complex at the Xichang Satellite Launch Center.

Chinese Moon Mission:

The Chang’e-3 mission is the second phase of China’s lunar program, a program that includes orbiting, landing and sample return ambitions. It is aiming to follow the successes of the Chang’e-1 and Chang’e-2 missions in 2007 and 2010.

The Chang’e-3 mission couples a lander and the rover, advancing China’s exploration ambitions exponentially.

With a launch mass of 3,780 kg, 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 main instrument is the Lunar-based Ultraviolet Telescope. This will be used to observe galaxies and other celestial objects.

Z3The lunar rover, named Yutu, will explore the lunar surface after departing the lander.

Yutu 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.

Yutu will be capable of real time video transmission, while it will be able to to dig and perform simple analysis of soil samples.

It carries a radar unit on its belly that allows for the first direct measurement of the structure and depth of the lunar soil down to a depth of 30 meters. The unit will also investigate the lunar crust structure down to depth of several hundred meters. The rover also sports an alpha particle X-ray spectrometer and an infrared spectrometer.

Z5Upon entering lunar orbit, Chang’e-3 will go through 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 will be controlled using 28 small thrusters.

Following deceleration, the vehicle will quickly adjust its attitude, approaching the lunar surface. During this phase the instruments will analyze the planned descent area. The main engine will be automatically shutdown at an altitude of four meters, allowing the rover to free fall on the surface.

Yutu (Jade Rabbit), the autonomous moon rover that will detach from the lander, will be controlled when necessary by scientists on Earth.

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The rover uses six wheels that are individually powered, using a suspension system very similar to the one used on the NASA MER rovers and also on Curiosity.

Z8Landing is expected on December 14, at a landing site called Sinus Iridium (the Bay of Rainbows), a relic of a huge crater 258 km in diameter.

China’s “Long March to the Moon” began in 1998 when the Commission for Science, Technology and Industry for National Defense (COSTIND) began planning the lunar mission, the tackling major scientific and technological problems.

The lunar orbiter project was formally established in January 2004, with the program named “Project Chang’e”, after a mythical Chinese goddess who flew to the moon.

Z9The first mission, Chang’e-1, was successfully launched on October 24, 2007, entering in lunar orbit on November 7.

Following the transmission of the Chinese song “Ode to the Motherland” and a number of images, the probe impacted the moon on March 1, 2009.

Chang’e-2 was launched aboard a Long March 3C rocket on October 1, 2010.

Arriving October 9 on a circular orbit 100 km over the lunar surface after a 112 hour flight, six engineering objectives and the four scientific missions were completed on April 1, 2011, including surveys of the south and north poles of the moon, taking high-resolution pictures of the chosen landing site for Chang’e-3.

The extended mission saw the probe depart towards a close encounter with the asteroid Toutatis.

Launch vehicle and launch center:

Developed from the Chang Zheng-3A, the Chang Zheng-3B is the most powerful launch vehicle on the Chinese space launch fleet.

The CZ-3B features enlarged launch propellant tanks, improved computer systems, a larger 4.2 meter diameter payload fairing and the addition of four strap-on boosters in the core stage that provide additional help during the first phase of the launch.

The rocket is capable of launching a 11,200 kg satellite to a low Earth orbit or a 5,100 kg cargo to a geosynchronous transfer orbit.

The CZ-3B/E (Enhanced Version) launch vehicle was developed from the CZ-3B, increasing the GTO capacity up to 5,500kg. The CZ-3B/E has nearly the same configurations with CZ-3B bar its enlarged core stage and boosters.

On May 14, 2007, the first flight of CZ-3B/E was performed successfully, accurately sending the NigcomSat-1 into pre-determined orbit. With the GTO launch capability of 5,500kg, CZ-3B/E is dedicated for launching heavy GEO communications satellite.

The Xichang Satellite Launch Centre is situated in the Sichuan Province, south-western China and is the country’s launch site for geosynchronous orbital launches.

Equipped with two launch pads (LC2 and LC3), the centre has a dedicated railway and highway lead directly to the launch site. The Command and Control Centre is located seven kilometers south-west of the launch pad, providing flight and safety control during launch rehearsal and launch. The CZ-3B launch pad is located at 28.25 deg. N – 102.02 deg. E and at an elevation of 1,825 meters.

Other facilities on the Xichang Satellite Launch Centre are the Launch Control Centre, propellant fuelling systems, communications systems for launch command, telephone and data communications for users, and support equipment for meteorological monitoring and forecasting.

The first launch from Xichang took place at 12:25UTC on January 29, 1984, when the CZ-3 Chang Zheng-3 (CZ3-1) was launched the Shiyan Weixing (14670 1984-008A) communications satellite into orbit.

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