Two "ZDPS-1A", China's smallest satellites, have been operating smoothly in orbit and performed well in technical tests during the past nine days after being launched into space, the developers told Xinhua Friday.

"The satellites are travelling around the earth once every 96 minutes, and they have accomplished all their planned tasks," said Jin Zhonghe, director of the Research Center of Micro-satellite with Zhejiang University in eastern Zhejiang Province.

On Sept. 22, China sent a remote-sensing satellite, named "Yaogan XI", and two "ZDPS-1A" satellites into space from the Jiuquan Satellite Launch Center in northwestern Gansu Province.

Soon after the "ZDPS-1A" satellites were launched into orbit they began testing their key technologies and sent back high-resolution pictures of the earth's surface, Jin said.

It was the first time China has successfully launched a wholly self-developed pico-satellite, which referred to small satellites weighing only kilograms, he said.

As China's smallest satellite, the "ZDPS-1A", weighing 3.5 kilograms, has a cube shape with a side length of 15 centimeters and requires a working power source of only 3.5 watts.

In contrast to large satellites, pico-satellites boast a low cost and a shorter period for manufacturing and launch preparations, Jin said.

"It often takes at least one billion yuan (about 149 million U.S.dollars) to build a large satellite, compared with only millions of yuan and several months for a pico-satellite," he said.

"Similarly, a large satellite needs no less than 30 to 40 days to blast off after it is sent to the launch center, while the period can be reduced to several days for a pico-satellite," said Wang Huiquan, another expert with the research center.

Due to such advantages, the pico-satellites were expected to play an important role in natural disaster-reduction, such as providing emergency communications and surveying the disaster-stricken areas, Jin said.

Nine days after the pico-satellites were launched, China's second unmanned lunar probe, Chang'e-2, lifted off on Friday.

At 6:59:57 p.m., the Chang'e-2, sitting atop a Long March 3C carrier rocket, was launched from the Xichang Satellite Launch Center in southwestern Sichuan Province.