BEIJING, Jan. 5 (Xinhua) -- The service module of China's unmanned lunar orbiter is scheduled to return to the moon's orbit in mid-January for more tests to prepare for the country's next lunar probe mission, Chang'e-5.

On Sunday, the service module left the Earth-Moon second Lagrange Point (L2) after circling the point while performing additional tests, the State Administration of Science, Technology and Industry for National Defense (SASTIND) said Monday.

A lunar orbiter is a spacecraft that orbits the moon, and its service module contains support systems used for spacecraft operations.

As of Monday, the service module was 445,000 kilometers away from Earth and 57,000 km from the moon. All experiments are operating smoothly.

The service module was separated from the test lunar orbiter's return capsule on Nov. 1, and the return capsule returned to Earth on Nov. 1 after circling the moon during its eight-day mission.

China's lunar orbiter program was the world's first mission to the moon and back in some 40 years, making China the third nation to complete a return mission to the moon after the Soviet Union and the United States.