On October 24 China took a step into space with the takeoff of the country's first circumlunar satellite, Chang'e-1. The launch represented a move toward realizing the country's ambition to become a major power in outer space.

"The lunar probe is an important stimulus for China's scientific development, a significant demonstration of China's overall national capacity and a promotion of its national prestige on the international stage," said Luan Enjie, Chief Commander of the country's lunar orbiter project.

As the most sophisticated satellite Chinese experts had ever handled, Chang'e-1 had been maneuvered at least 10 times over the next fortnight, covering more than 1 million km before it finally arrived in the moon's orbit on November 5 after entering Earth-moon transfer orbit on October 31.

With a total investment of 1.4 billion yuan (about $180 million), the lunar orbiter, the first made by a developing country, is one of the cheapest in history.

Self-innovation

According to the space plan, the satellite will relay its first pictures of the moon in late November and will then continue scientific exploration of the moon for a year, measuring its temperature using microwave radiation technology, estimating the depth of the lunar crust and exploring the environment between the moon and the Earth.

Building the lunar probe required high levels of technology in many areas including rocketry, communication, monitoring and control, remote sensing, and research apparatus, according to Luan.

"These will provide us with the impetus to make rapid advances in China's science and technology so that in the near future China can get its own first-hand materials from the moon," he said.

Circling 200 km above the Earth's surface, the lunar orbiter will use stereo cameras and X-ray spectrometers to map 3-D images of the lunar surface. Currently there are no such 3-D images available anywhere in the world.

"The images will help us better understand the structure of the moon," said Ye Peijian, Chief Designer and Commander in Chief of the satellite system of China's lunar probe program.

"We will explore 14 group elements of great importance on the moon's surface. The United States only studied five groups," said Ye.

The Chinese lunar probe is equipped with an efficient payload data managing system to collect, store, process and transfer data, said Ye.

"The lunar project represents the development of China's self-innovation capacity in terms of the exploration of outer space, which is also a contribution to the world," he added.

The investment in the lunar probe project is not astronomical for China's economy; however, it will greatly boost the development of national science and technology, said Ouyang Ziyuan, Chief Scientist of the lunar exploration program.

Complex orbits

"The launch of China's first lunar probe Chang'e-1 is just step-one for the country's deep space exploration plan. To accomplish the first scientific objective Chinese scientists have overcome four major difficulties," said Ye.

The first difficulty was the design of the probe's orbits. The orbit design of previous satellites was easier than that of Chang'e-1, because this time the probe has to take into consideration the motion of three objects: the Earth, the orbiter and the moon. In the previous astronomic exploration missions the moon has not been involved.

After careful and repeated study and calculation, Chinese scientists working on the project worked out the complex orbits. Firstly, a rocket sends the probe to the outer space. After three orbit transfers the probe is expected to enter the Earth-moon transfer orbit, a critical point that may determine whether the satellite can fly to the moon successfully or not, according to experts at the Beijing Aerospace Control Center.

The second problem for the probe is heat, both on its surface and inside of the orbiter. High standards are required of the electronic components in the orbiter, which will face a critical space environment where the temperature fluctuates drastically between 130 degrees centigrade and minus 170 degrees centigrade. Temperature control technology on the probe has to be flexible to the environment to ensure that all the parts of the orbiter continue to operate.

The probe's remote monitoring and communication systems also require more advanced technology than used during previous astronomic missions, all of which have been within 70,000 km of the Earth. Chang'e-1 will venture 380,000 km from the Earth, creating new challenges for communication.

Meanwhile the probe's complicated orbit shifts have increased the complexity of ground monitoring and control, said Ye. China does not yet have a deep space monitoring network and remote control operations on the probe will be mostly accomplished via the joint efforts of astronautic and space monitoring networks.

The last obstacle is the positioning of the orbiter, which has to be kept at certain positions relative to the Earth, moon and sun.

"Overcoming all these difficulties requires technological innovation, which involves many frontier technologies," Ye noted, adding that overcoming the problems will lead to huge developments in science.

No space race

The launch of the lunar orbiter marks the first step of China's three-stage moon mission, which will lead to a moon landing and launch of a moon rover in 2012. In the third phase, another rover will land on the moon and return to the Earth with lunar soil and stone samples for scientific research in 2017.

China carried out its maiden piloted space flight in October 2003, making it the third country in the world after the former Soviet Union and the United States to have sent men into space. In October 2005, China completed its second manned space flight, with two astronauts on board.

The launch of Chang'e-1 came shortly after Japan launched its first lunar probe, Kaguya, in mid-September, while India is planning to send its own lunar probe into space next April, sparking off concerns of a space race in Asia.

But Luan said, "China will not get involved in moon race with any other country and in any form."

He added, "China will, in pursuing its policy of peaceful use of airspace, share the achievements of its lunar exploration with the whole world."