China will launch a sample return mission to the Moon in 2017, officials say, while declaring complete success for the current Chang’e 3 mission to land and deploy a lunar rover.
The next mission, Chang’e 4, will be similar to the current effort, using a backup spacecraft and rover, but will be adapted to prove technologies for the sample-return mission, Chang’e 5, says Wu Zhijian, a spokesman for the State Administration of Science, Technology and Industry for National Defense.
Wu gave no schedule for Chang’e 4, but last year it was slated for 2015.
In 2017 Chang’e 5 will be China’s first space expedition to land on the Moon, collect samples and return them to Earth. Chang’e 6 is designed to do the same, following China’s habit of planning a pair of missions for each stage of its program to explore the Moon, in case of failure.
Stage two, to land and deploy a rover, has succeeded, says Ma Xingrui, chief commander of the lunar program and formerly the president of China Aerospace Science and Technology Corp., which builds most of the equipment for the lunar exploration program.
Chang’e 3 landed at 1:11 p.m. GMT on Dec. 14 and deployed its 140-kg (300-lb.) rover about seven hours later. On Dec. 15 the lander and rover began demonstrating their operational capability by photographing each other.
The rover, called Jade Rabbit, is intended to examine the Moon’s geological structure and surface material and look for natural resources for the next three months, although U.S. experience suggests that it could operate for much longer. The lander, unable to move, is to observe its surroundings for a year.
China’s lunar exploration program began in 2007 with the launch of Chang’e 1, a spacecraft built on a DFH-3 satellite bus, was launched into orbit around the Moon and finally crashed on to its surface. Chang’e 2, a very similar spacecraft built as a back-up, improved on its predecessor in 2010 by being launched directly into a lunar transfer orbit. Among the tasks of that mission was surveying possible landing sites for Chang’e 3. That completed stage 1, although Chang’e 2 is still operational, heading into deep space and now 60 million km (37 million mi.) from Earth.
No details are available on how Chang’e 4 will be adapted to lay groundwork for the third-phase sample-return missions, but Wu tells state news agency Xinhua: “The program’s third phase will be more difficult because many breakthroughs must be made in key technologies, such as Moon surface takeoff, sampling encapsulation, rendezvous and docking in lunar orbit, and high-speed Earth reentry, which are all new to China.”
Chinese space engineers and scientists hope to follow the third phase by sending people to the Moon, perhaps in the late 2020s, but they do not have approval for such a program.
Chang’e 2’s surveys helped with the choice of the plain called Sinus Iridium as the landing spot. Taking advantage of technological advances since the last lunar landings 37 years ago by the Soviets, the Chinese engineers fitted Chang’e 3 with a system for autonomously evaluating its touchdown location during descent.
The descent began with the main braking phase at an altitude of 15 km in which, according to the published plan, velocity was to be reduced from 2,000 meters per sec. 70 meters per sec. by the time it reached 2.4 km altitude. Following further braking, at an altitude of 100 meters (330 ft.) the lander was to hover for less than 30 sec. to survey the terrain before dropping to 30 meters while maneuvering to avoid obstacles.
At 30 meters the 7.5 kilonewton (1,690 lb.) variable-thrust engine was expected to kick up dust from the surface; the rate of descent was then to be reduced to 2 meters per sec. At 3 meters, the engine was to shut down for a free fall to the surface.
Jade Rabbit, with six wheels, will move at speeds up to 200 meters an hour. It has three pairs of sensors, for navigation, panoramic imaging, and obstacle avoidance. With solar panels folded, it is 1.5 meters long, 1 meter wide and 1.1 meters high.