An artistic rendition of the docking of Chinese cargo spacecraft Tianzhou-1 with the Tiangong-2 space experimental space lab.
Photo is courtesy of CASC.

China's Tianzhou-1 cargo spacecraft has completed its second docking with Tiangong-2 space lab at 2:55 p.m. Monday, after flying around the space lab, according to a news report on the Xinhuanet infosite.

Tianzhou-1 separated from Tiangong-2 on Monday morning and remained at distance of five kilometers behind the space lab for about 90 minutes. Then, it was commanded to fly around Tiangong-2 from behind to a distance of five kilometers in front of the space lab. During the flight, both Tianzhou-1 and Tiangong-2 turned in a semicircle. The experiments tested docking technology at different directions, which is of great importance to building a space station, according to the China Manned Space Engineering Office.

Tianzhou-1, China's first cargo spacecraft, was launched on April 20 from south China's Hainan Province, and it completed automated docking with the orbiting Tiangong-2 space lab on April 22. The two spacecraft completed their first in-orbit refueling on April 27 and their second in-orbit refueling on June 15.

China is the third country, after Russia and the United States, to master refueling techniques in space, which is crucial in the building of a permanent space station. As the International Space Station is set to retire in 2024, the Chinese space station will offer a promising alternative — China will be the only country with a permanent space station.