China's first lunar probe satellite, Chang'e 1, will have its solar energy supply tested on Sunday, when the earth eclipses the sun.
This will be the satellite's second such challenge this year, after it successfully ran on battery power for two hours during a full eclipse on Feb. 21.
Sunday's eclipse would occur between 3:35 a.m. and 6:44 a.m., when the satellite would be hidden from the solar rays and switch to batteries, said Wang Sichao, a research fellow with Zijinshan (Purple Mountain) Astronomical Observatory.
"The moon's shadow, also a signal blind area, could cause a power shortage in freezing temperatures," he said.
In the first eclipse, scientists altered the orbit of the satellite to shorten the time it was out of direct sunlight. Some facilities were also temporarily switched off to save power.
The 2,350-kilogram satellite, which has been in orbit for nine months, carries eight surveying facilities to make a three-dimensional survey of the moon's surface.
Chinese scientists monitoring the system say it is in good condition, and expect it to work for another year, though it has a designed life of one year.
The launch of the lunar probe is the first step in China's three-stage moon mission, which will lead to a landing and launch of a rover vehicle around 2012. In the third phase, another rover will land and return to the Earth with lunar soil and stone samples for scientific research around 2017.