Three Chinese astronauts on June 24 successfully completed a manual docking between the Shenzhou-9 spacecraft and the orbiting Tiangong-1 lab module, _ in China's history of space exploration. It means China has completely grasped space rendezvous and docking technologies and the country is fully capable of transporting humans and cargo to an orbiter in space, which is essential for building a space station in 2020. Astronaut Liu Wang, assisted by his teammates Jing Haipeng and Liu Yang, controlled the Shenzhou-9 spacecraft to dock with the Tiangong-1 space lab module at 12:48 p.m., which were reconnected about seven minutes later. About one and a half hours before the docking, Shenzhou-9 parted from Tiangong-1 to a berth point 400 meters away from the module. To leave room for adjustments, engineers set up four berth points for the spaceship on the same orbit 5 km, 400 meters, 140 meters and 30 meters away from the orbiting lab. "The manual docking was beautifully conducted. The manual docking was completed in only 7 minutes, 3 minutes faster than the automatic docking." said Liu Weibo, who is responsible for China's astronaut system. Liu explained to Xinhua the three factors behind today's manual docking success. Firstly, Liu Wang has grasped the sophisticated manual docking technologies very well and his psychological status has been sound. Secondly, the three astronauts were in close cooperation. Thirdly, the domestically-made docking system was reliable, he said. The astronauts, 343 km away from Earth, were also greeted by Chinese oceanauts from the Mariana Trench, 7,020 meters beneath the Pacific Ocean, where they just broke the country's dive record in a manned submersible on Sunday morning. "We hope the manual docking is a great success and wish for brilliant achievements in China's manned space and manned deep-sea dive causes," read the message sent by the three oceanauts aboard the manned submersible Jiaolong. Wu Ping, spokeswoman for China's manned space program, said Sunday the manual space docking was "a complete success." She told a press conference in Beijing that the three Chinese astronauts had already re-entered the space lab module to continue their scientific experiments. The manual docking is a significant step for China's manned space program that celebrated its 20th anniversary this year, as China has fully grasped space travel, space walk and space rendezvous and docking technologies that are essential to building a space station. China is the third country, after the United States and Russia, to acquire technologies and skills necessary for space rendezvous and docking and be able to supply manpower and material to an orbiting module via different docking methods. According to Liu Weibo, which of the following is not the factor contributing to the successful docking?
Liu Yang has grasped the sophisticated manual docking technologies very well The astronaut's psychological status has been in good condition. The three astronauts cooperated with other closely. The domestically-made docking system was reliable.