Towards the middle of this month, China intends to achieve a major landmark in space exploration with its recently-launched Chang’e-3 mission — to make a soft landing on the Moon, a technological capability that has thus far been demonstrated only by the Soviet Union and the United States.
After getting into orbit around the Moon, the Chang’e-3’s lander is to carry out a carefully controlled descent and touchdown on the Sinus Iridum (Latin for ‘Bay of Rainbows’), a flat lava-filled lunar crater. A six-wheeled rover will then roll down from the lander and set off across the lunar surface.
Influential Chinese scientists began urging their Government to undertake a programme of lunar exploration in the early 1990s. But the Communist Party’s Central Committee finally gave the go-ahead only a decade later, in January 2004.
China’s current lunar programme involves three stages — orbiting the Moon, landing on its surface and, finally, bringing back lunar samples.
In 2007, a year before India launched its Chandrayaan-1 lunar probe, China sent the Chang’e-1 spacecraft to image and study the Moon from orbit.
Three years later, the Chang’e-2 was despatched, which too orbited the Moon and took high-resolution images that helped choose the landing site for its successor.
After the spacecraft’s primary mission was completed, its controllers sent it about 1.5 million km from Earth. Thereafter, it conducted a fly-by of the asteroid Toutatis about seven million km from Earth. The Chang’e-2 was currently about 60 million km away and would travel to a distance of 300 million km, according to a senior Chinese official quoted in a Xinhua news agency report.
The Chang’e-3’s lander, which is now on its way to the Moon, will use a liquid propellant engine, with variable thrust, to slow the spacecraft as it descends to the lunar surface. The lander has been provided with an autonomous capability to hover above the lunar surface, check for obstacles below and, if necessary, to move away from them before touching down, according to a paper published by Chinese space scientists.
“Autonomous hazard avoidance is a capability that NASA has tested on Earth, but has not yet flown on any lander spacecraft,” commented Dwayne Day, an American space historian and analyst, in an article in The Space Review , an online publication.
Apart from transporting the rover, the lander is carrying a near-ultraviolet telescope for astronomical observations as well as an extreme ultraviolet camera to observe a region of charged particles around Earth.
The 140-kg rover has a robotic arm that can analyse the chemical composition of lunar rocks and soil. It also carries a ground-penetrating radar to provide information about the Moon's crust.
Both the lander and rover are equipped with radioisotope heating units, containing radioactive plutonium-238, to keep them warm during the long lunar nights when temperatures can plunge to -150 degrees Celsius. This will be another important first for China as radioisotope-based systems to produce electricity and for heating spacecraft are widely used in deep space missions.
This mission will be followed by another lander-rover effort, the Chang'e-4. Then, with the Chang'e-5 currently scheduled for 2017, China will attempt to bring back lunar rock and soil samples.
Given China’s steady progress in manned space, many believe that its next step will be to land astronauts on the Moon. Indeed, Ouyang Ziyuan of the Chinese Academy of Sciences, who played a key role in promoting lunar exploration, has been quoted as saying that manned missions would follow.
“I do not believe China has made a decision on a human lunar mission,” observed Gregory Kulacki, China project manager and senior analyst at the Union of Concerned Scientists, a U.S.-based nonprofit science advocacy group.
China’s space station was the terminal goal of its current manned spaceflight programme, and would keep its space planners occupied for more than a decade, he pointed out in an email. There were also some doubts emerging about the value of the human programme relative to other emerging space priorities.
Besides, “China appears to prefer an international, collaborative effort when discussing possible human lunar missions, rather than going alone,” remarked Dr. Kulacki, who has written extensively about its space programme.
