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)