China's lunar probe Chang'e-1 successfully carried out its first orbital correction Friday morning in a bid to ensure that it travels on the pre-set orbit.
Instructions for the orbital correction was issued by the Beijing Aerospace Control Center (BACC) at 10:25 AM Friday, when two small engines on Chang'e-1 were ignited to slightly modulate its trajectory.
Eight minutes later, the two engines stopped working and the orbital correction completed.
"Data show we have reached our expectation through the orbital correction," said Wang Yejun, the BACC's chief engineer.
Chang'e-1 now is moving the earth-moon transfer orbit with the apogee of about 380,000 km and it is expected to reach the moon's orbit at 11:25 AM Monday.
The orbital correction, which was planned to be conducted on Thursday, was canceled as the probe was traveling on the expected trajectory in an "unexpected precisely" way after it left the earth orbit late Wednesday, said Wang.
"That's also the reason why we didn't employ the main engine on the Chang'e-1 for the first orbital correction, because it is not necessary and it also saves energy for the orbiter's future operation," he said.
A second orbital correction might be carried out Sunday, said Wang.
Pang Zhihao, a researcher with the China Academy of Space Technology, said orbital correction is necessary to prevent an orbiter from veering off its projected course.
"An aircraft faces many disturbances, such as gravitation from celestial bodies, when it travels in space, so we have to carry out corrections to ensure it moves on the right track," said Pang.
"Just like driving a car, we must keep turning the steering wheel to ensure the car running right on the roadway," said Pang.
Chang'e-1, named after a mythical Chinese goddess who, according to legend, flew to the moon, blasted off on a Long March 3A carrier rocket at 6:05 PM of Oct. 24 from the Xichang Satellite Launch Center in the southwestern province of Sichuan.
It entered earth-moon transfer orbit on Wednesday and is expected to arrive at the moon's orbit at 11:25 AM on Nov. 5.
Chang'e-1 will brake several times then to slow down so that it can be captured by the lunar gravity and become a real circumlunar satellite.
It would relay the first picture of the moon in late November and would then continue scientific explorations of the moon for a year.
China's lunar orbiter project has cost 1.4 billion yuan (US$187 million) 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 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 around 2017.
China carried out its maiden piloted space flight in October 2003, making it only the third country in the world after the 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.
(Xinhua News Agency November 2, 2007)
