Chang'e-2, China's second unmanned lunar probe which was launched on Oct 1, is expected to arrive in the moon's orbit at about 11 am on Wednesday, the Beijing Aerospace Control Center (BACC) said.

The spacecraft will enter the 100-km lunar orbit in roughly its 112th hour in space compared to the 13 days its predecessor Chang'e-1 took to reach the orbit three years ago, the control center said.

Chang'e-2, which is part of China's three-phase space program that aims to land an astronaut on the moon around 2020, will be maneuvered into an orbit just 15 km above the moon by the end of this month, Xie Jianfeng, director of the center's orbit room, said.

From that height, the satellite will be able to take high-quality photographs of the proposed landing sites for Chang'e-3 and future moon missions with a resolution of 1.5 meters, a dramatic improvement from that of the camera onboard Chang'e-1, said Wu Weiren, chief designer of the country's lunar orbiter project.

Since blasting off from the Xichang Satellite Launch Center in Southwest China's Sichuan province on Friday evening, Chang'e-2 has been doing well in space, with the cancellation of two planned orbital adjustments following a "highly accurate" trajectory correction on Saturday, BACC director Zhu Mincai said.

The control center had already received an initial batch of data, totaling 1.6 gigabyte (GB), from the satellite as of 7 am on Tuesday, according to China Central Television (CCTV).

But the mission cannot be declared a success until the probe relays back clear images of the Bay of Rainbows - the planned landing site for Chang'e-3 - taken from the 15-km orbit, said a spokesman for the lunar exploration program.

The Chang'e-2 mission is a "starting point" of the second stage of China's lunar exploration program, he said.

The mission costs 900 million yuan ($ 134 million), down from the 1.4 billion yuan poured into Chang'e-1.

Chang'e-3 is expected to blast off from the country's fourth and latest satellite launch center in Wenchang, South China's Hainan province, before 2013, Luan Enjie, former director of the China National Space Administration, was quoted as saying in the Guangzhou-based Southern Daily.

Chang'e-3 is expected to make a soft landing in the Bay of Rainbows area on the moon, where it will deploy a lunar rover for a 90-day exploration mission within a 5-square-km radius, Luan said.

In the third phase of the lunar exploration project, a spacecraft will be sent to the moon to collect and send back surface samples by 2017.

Wu said a manned lunar landing, which completely depends on the successful completion of the project, would happen "some time after 2020".

Meanwhile, Ouyang Ziyuan, the project's chief scientist, placed his estimate at between 2020 and 2025.