Chang'e 3

Chang’e 3 is the third robotic lunar probe mission of the China Lunar Exploration Programme (CLEP). Scheduled to be launched in December 2013, the probe will soft-land on the Moon surface and deploy an unmanned Lunar Rover to explore the areas surrounding the landing spot. The mission is heded by the State Administration of Science, Technology and Industry for National Defence (SASTIND) and the primary contractor for the probe is the China Academy of Space Technology (CAST) of the China Aerospace Science & Technology Corporation (SASC).

The Spacecraft

Chang’e 3 lunar probe consists of two modules: the Service Module and the Lunar Landing Vehicle (着陆器), with a total mass of 3,700~3,800kg. The spacecraft will be launched onboard the CZ-3B rocket from the Xichang Satellite Launch Centre, and will be controlled by the ground via the X-band very long baseline interferometry (VLBI) system upgraded with 64m and 35m diameter antennas.

The spacecraft will be firstly parked into a 100X100km lunar orbit. After separating from the Service Module, the Lunar Landing Vehicle will descend to a 100X15km, 45° inclined elliptic orbit. When reaching the 15km perigee, the vehicle will ignite its variable thrusters to reduce its velocity, so that it slowly descends to 100m above the Moon surface. The vehicle will hover at this altitude, moving horizontally under its own guidance to avoid obstacles, and then slowly descend to 4m above the ground, at which point its engine will shut down for a free-fall onto the lunar surface.

Five locations have been considered for the landing spot of Chang'e 3, including Sinus Iridum, Mare Nectaris, Mare Humorum, Kepler crater, and Aristillus crater. Among these Sinus Iridum is the first choice for the Chang'e 3 mission. High-definition images of the area has been captured by the Chang'e 2 lunar orbiter launched in 2010.

The Lunar Landing Vehicle is China’s first nuclear-powered spacecraft, equipped with a radioisotope thermoelectric generator (RTG) in order to support its operations during long Moon-nights. The vehicle has a total mass of 1,200kg, and a designed operational life of 12 lunar months. Once successfully landing on the Moon, the vehicle will deploy a six-wheeled Lunar Rover to explore the surrounding areas.

Lunar Rover

The Automatic Lunar Surface Exploring Vehicle (自动月面巡视器), or more commonly known as "Lunar Rover" (月球车), is a solar-powered, wheeled robotic vehicle that can propel itself across the lunar surface after landing. The first lunar rover, designed and built by the China Academy of Space Technology (CAST), will land on the Moon in 2012~13 onboard the Chang’e 3 lunar exploration spacecraft.

The six-wheeled lunar rover has a designed life of 90 lunar days, and can explore an area of 3 square kilometres, with a maximum travelling distance of 10km. It has a total mass of 120kg, and can carry up to 20kg payload.

The vehicle is capable of autonomously navigating around, avoiding obstacles, selecting the most optimised routes and locations for exploration activities. Onboard equipment includes a radar for detecting the structure beneath the Moon surface and an optical telescope. The onboard camera can capture images of the lunar surface. A mechanical collector designed by the Hong Kong Polytechnic University allows the vehicle to collect lunar soil samples for analysis.

The vehicle can transmit image and data back to the Earth in real-time. All equipments are capable of operating normally at -180°C during the Moon-night.

The Launch Vehicle

Chang'e 3 will be launched atop an enhanced variant of the CZ-3B launch vehicle from the Xichang Satellite Launch Centre. The launch vehicle featured six improvements specifically tailored for the mission. They include a dual laser-inertial / GPS guidance system which allows much improved orbit insertion accuracy, increased launch windows, and an 1,300 kg increase in its payload capacity.

Chang'e 3 Mission Timeline

November 2009 - The concept design of the Chang’e 3 probe was approved by SASTIND and CAS. The programme entered the prototype development stage.

November 2011 - The simulated hovering and soft-landing of the lunar landing vehicle and the field test of the lunar rover succeeded.

March 2012 - The prototype development of Chang'e 3 had been completed and the development of the flying example commenced. This key milestone of the programme came 10 months later than the original target date.