BEIJING, March 14 (Xinhua) -- China's moon rover Yutu woke up again at 6:42 a.m. on Friday, after its third dormancy, but even after a long rest, mechanical problems have not been resolved.

Yutu and the lander, which woke up earlier on Wednesday, have restarted their operations and are exploring as scheduled, according to the State Administration of Science, Technology and Industry for National Defence (SASTIND).

The control issues that have troubled Yutu since January remain, but its panorama camera, radar and other equipment are functioning normally, SASTIND said.

The cause of the problems is a mystery. The lander functioned normally during its first three lunar days, according to the SASTIND. A lunar day is equivalent to about two weeks on Earth.

The lander's optical telescope, extreme ultraviolet camera and lunar dust measurement device completed scheduled tasks and obtained a large amount of data.

It has now survived its design life of three months.

The rover was intended to roam the lunar surface, surveying the geological structure and substrate while looking for natural resources, but problems emerged before the second dormancy on Jan. 25 as the lunar night fell. According to SASTIND, the problem was caused by the "complicated lunar surface."