China's first lunar probing satellite, Chang'e-1, adjusted its operating orbit on Sunday night to avoid a power shortage during an upcoming moon eclipse, Xinhua learned on Tuesday.
The satellite's engine was ignited at 11:50:48 p.m. on Sunday. It lifted Chang'e-1, at an altitude of 200 kilometers above the moon's surface, up to an orbit nearly 2 km higher in more than 60 seconds, the Beijing Aerospace Control Center (BACC) said.
A moon eclipse on Feb. 21 will cut off the sunlight supply for Chang'e-1 for three to four hours. The adjustment, however, will shorten the time to two hours, ensuring enough solar power for the orbiter, said Zhu Mincai, BACC director.
Launched via a Long March rocket on Oct. 24 from southwest China, Chang'e-1 is powered mainly by solar power panels. Its batteries can provide electricity only for a short period.
The eclipse will coincide with this year's traditional Chinese Lantern Festival when the moon and the orbiter will be wholly shadowed by the Earth, Zhu said.
Only a few facilities will be temporarily switched off during the eclipse. This won't strongly affect the satellite's work in general, said BACC scientist Liu Congjun.
"We made the adjustment more than 20 days ahead of the eclipse so as to save fuel and avoid negative effects by too large orbital changes on scientific exploration," said Tang Geshi, a BACC official in charge of orbital control.
The satellite will perform an orbital adjustment again when another eclipse occurs in August, Liu said.
He added all facilities on Chang'e-1 were functioning well to carry out the lunar probing missions as planned.
The 2,350-kilogram satellite, carrying eight probing facilities, aims to make a three-dimensional survey of the moon's surface. It will also analyze the abundance and distribution of elements on the lunar surface,investigate the characteristics of lunar regolith and the powdery soil layer on the surface, and explore conditions between the Earth and the moon.
The launch of the orbiter kicks off the first step of China's three-stage moon mission, which will lead to a moon landing and launch of a rover vehicle 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.
The latest data from the BACC showed that Chang'e-1 had an error rate as small as 3/10,000 in its orbital accuracy, a result of more than 120 orbital calculations that have been done since the satellite entered its orbit.
Tang said that the statistics demonstrated a breakthrough in China's aerospace control skills in deep space exploration, which used to be an unexplored area of the country's scientific research.
The satellite is flying at high speed, with delays in its communication with the ground, both of which made it much more difficult to measure and control the orbit, said Liu.
After a 12-day flight, Chang'e-1 entered the moon's orbit on Nov. 5, only 20 seconds away from the predicted moment of reaching orbit, said Tang.
During Chang'e-1's 1,580,000-km journey to the moon, improvement in the accuracy of orbital controls saved the satellite more than 190 kg of fuel, or as much fuel it needed to orbit the moon for two years.
(Xinhua News Agency January 30, 2008)