Chinese spacecraft dock in orbit
The unmanned Shenzhou 8 craft, launched earlier this week, made contact with the Tiangong-1 space lab at 1729 GMT. The union occurred over China itself.
Being able to dock two space vehicles together is a necessary capability for China if it wants to start building a space station towards the decade's end.
Although no astronauts were in the Shenzhou craft this time, future missions will carry people.
Tuesday's procedure (Beijing time 0029, Thursday) took place at an altitude of about 340km. It was automated but overseen on the ground at the Beijing Aerospace Flight Control Centre.
The vehicles used radar and optical sensors to compute their proximity to each other and guide their final approach and contact. A video feed from orbit showed the final moments of the vehicles coming together.
Shenzhou 8 was the active craft in the docking. It fired its thrusters to push its front end towards the docking port of Tiangong-1. Once the vehicles' docking rings had made a good capture, 12 hooks were deployed to fix the craft in place. Protruding pins made electrical connections.
From first contact to confirmation of a seal took about 10 minutes.
Shenzhou 8 and Tiangong-1 will spend two weeks circling the globe together before Shenzhou 8 heads back to Earth.
"After a joint flight of about 12 days, they will separate," explained Prof Yang Yuguang from the China Aerospace, Science and Industry Corporation.
"Then the Shenzhou 8 will draw back to about 140m. After that they will perform a second docking. Then they will have a flight of two days. Then they will be separated to about 5km; this will be a safe distance for both vehicles. Then the re-entry procedure will be performed by the Shenzhou 8 spaceship," he told state broadcaster China Central Television (CCTV).
The return capsule will land by parachute to allow experiments carried into orbit to be recovered for analysis. The German space agency (DLR) has supplied an experimental box containing fish, plants, worms, bacteria and even human cancer cells for a series of biological studies.
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