The circumlunar satellite Chang'e-1 blasted off on a Long March3A carrier rocket at 6:05 p.m., Oct.24 from the No. 3 launching tower in the Xichang Satellite Launch Center of southwestern Sichuan Province. (Xinhua/Li Gang)

    BEIJING, Oct. 29 (Xinhua) -- China's lunar probe Chang'e-1 completed its third orbital transfer on Monday afternoon, one more step forward in its 1,580,000-km journey to the moon.

    Instructions for the orbital transfer was issued by the Yuanwang-3 space tracking ship in south Pacific at around 5:56 pm.

    At around 6:01 pm, the probe was successfully transferred to a 48-hour orbit with an apogee of 120,000 km, up from the former 70,000 km.

    It will stay on the orbit until Oct. 31, when it 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 (BACC).

    Ultraviolet image sensors installed on the satellite will begin to work to collect information on the earth and the moon after it enters the 48-hour orbit, Wang Yejun, chief engineer with the BACC told Xinhua.

    It's the first time that an ultraviolet image sensor is put into actual use on a satellite, though a few countries had tested them on the ground, Wang said.

    The images Chang'e-1 collects will be transmitted back to the earth when it enters the lunar orbit, Wang said.

    Since Saturday, surveillance posts, on land and sea, and four astronomical observatories have kept watching over Chang'e-1. According to the data received so far, all systems of the satellite have been working normally.

    The lunar probe completed its first orbital change on Oct. 25, in which it was transferred to a 16-hour orbit with a perigee of about 600 km from 200 km.

    The probe completed its second orbital transfer on Oct. 26, which made it move on a 24-hour orbit with an apogee of 70,000 km, up from the former 50,000 km.

    Chang'e-1, named after a mythical Chinese goddess who, according to legend, flew to the moon, blasted off on a Long March3A carrier rocket at 6:05 p.m. on Oct. 24 from the Xichang Satellite Launch Center in the southwestern province of Sichuan.

    The 2,300-kg satellite is expected to arrive in the moon's orbit on Nov. 5. It carried eight probing facilities, including a stereo camera and interferometer, an imager and gamma/x-ray spectrometer, a laser altimeter, a microwave detector, a high energy solar particle detector and a low energy ion detector.

    It will fulfill four scientific objectives, including a three-dimensional survey of the Moon's surface, analysis of the abundance and distribution of elements on lunar surface, an investigation of the characteristics of lunar regolith and the powdery soil layer on the surface, and an exploration of the circumstance between the earth and the moon.

    The satellite will relay the first picture of the moon in late November and will then continue scientific explorations of the moon for a year.

    China's lunar orbiter project has cost 1.4 billion yuan (187 million U.S. dollars) since research and development of the project was approved at the beginning of 2004.

    The launch of the 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 at around 2012. In the third phase, another rover will land on the moon and return to earth with lunar soil and stone samples for scientific research at around 2017.

    China carried out its maiden piloted space flight in October 2003, making it only 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 Enjie, chief commander of China's lunar orbiter project, said that "China will not be involved in moon race with any other country and in any form."

    "China will, in the principle of pursuing a policy of peaceful use of airspace, share the achievements of the lunar exploration with the whole world," he told Xinhua.