China's first moon orbiter Chang'e-1 is expected to conduct its fourth orbital transfer, also the last before it leaves the earth orbit, on Wednesday afternoon.

Chang'e-1 moon orbiter is now moving on a 48-hour orbit with the apogee of more than 120,000 km. It will begin to enter the earth-moon transfer orbit with the apogee of about 380,000 km at around 6:00 p.m. on Wednesday, when it begins to fly to the moon in a real sense, said Zhu Mincai, head of the Beijing Aerospace Control Center (BACC).

The main engine of Chang'e-1 will be operational then and help raise the speed of the orbiter to 10.916 km per second in a few minutes before Chang'e-1 reaches the 'entrance' of the earth-moon transfer orbit, said Zhu.

"It's a success-or-failure point and we only have one shot as the fuel carried on the Chang'e-1 is limited," said Zhu. "If the orbiter misses the entrance and it will keep moving on the earth orbit instead of flying to the moon."

The lunar probe is estimated to fly another 114 hours before it reaches the moon orbit on Nov. 5.

China successfully launched the Chang'e-1, named after a mythical Chinese goddess who, according to legend, flew to the moon, on Oct. 24.

The lunar probe was transferred to a 48-hour orbit with an apogee of more than 120,000 km, up from the former 70,000 km, at 6:01 p.m. on Monday.

(Xinhua News Agency October 31, 2007)