Sunday 31 August 2008

Yuanwang Space Tracking Ships

Yuanwang Space Tracking Ships
The PLA Navy currently operates a fleet of four space tracking ships to support China’s intercontinental-range ballistic missile (ICBM) testing and space programmes. These ships, together with the land-based domestic and overseas space tracking stations, provide the PRC with a global space tracking, telemetry, and control (TT&C) network that can continuously detect, track, and control satellites and manned spacecraft in space. So far the four vessels, named Yuanwang 1~4, have carried out over 50 key missile testing and space flight support missions successfully.
The four Yuanwang space tracking ships have been heavily involved in China’s national manned space programme (Project 921) since 1999. In a typical ShenZhou spacecraft flight mission, Yuanwang 1 is positioned in the West Pacific off the Chinese coast; Yuanwang 2 is positioned about 1,500km southwest of French Polynesia in Southern Pacific; Yuanwang 3 is positioned off the Namibian coast in the Atlantic; Yuanwang 4 is positioned off the coast of Western Australian in the Indian Ocean. The four ships monitor the flight of the spacecraft, and also send command signals to the spacecraft for solar panel deployment, orbit maintenance manoeuvre, retrofire engine igniting, etc. Should the astronauts make an emergency escape and land in the sea, the Yuanwang ships will also be responsible for the search and rescue mission.

Yuanwang 1 and 2

In 1965, Premier Zhou Enlai first proposed the concept of China developing its own ocean-going space tracking ships. In July 1967, the Chinese leadership approved a large-scale shipbuilding project known as Project 718 to support China’s first full-range ICBM test flight from Shuang Cheng Zi missile test site in Northwest China to the target zone in the South Pacific. The project included two 21,000t missile and spaceraft tracking ships (Yuanwang 1 and 2), an ocean scientific survey ship (Xiangyanghong 10), and an ocean rescue ship (Dajiang class), all to be constructed by Jianan Shipyard in Shanghai.

The first missile and space tracking ship Yuanwang 1 was launched on 31 August 1977, followed by the second ship on 1 September 1978. In early 1980, a large naval task force consisting 20 surface ships departed from Shanghai to the South Pacific for the scheduled missile test. On 18 May 1980, a DF-5 (CSS-4) ICBM was launched from Shuang Cheng Zi and the warhead was successfully recovered by the naval task force waiting in the target zone in the South Pacific.

In the mid-1980s, Yuanwang 1 and 2 were also involved in the full-range test flight of the JL-1 (CSS-N-3) submarine-launched ballistic missile (SLBM) and the tracking of s first geostationary orbit communications satellite DFH-2 and the third-stage of its CZ-3 launch vehicle. In 1986, the two ships received their first modernisation refit to support commercial launch services for international customers. In the late 1990s, Yuanwang 1 and 2 received their second major refit to support the flight missions of China’s ShenZhou manned spacecraft.
By 2005, Yuanwang 1 had successfully undertaken 41 voyages for 38 missile and satellite tracking missions, totalling some 1,500 days of operation in the sea and covering a total distance of 270,000 nautical miles. During the ShenZhou 5 manned space flight mission, Yuanwang 1 positioned in the Sea of Japan captured the spacecraft’s signal 9 minutes after its separation from the launch vehicle and commanded the spacecraft to deploy its solar panels. During the ShenZhou 6 flight mission, Yuanwang 1 positioned in the West Pacific captured the spacecraft signal only 31 seconds after its separation from the launch vehicle and successfully commanded the spacecraft to deploy its solar panels.

Yuanwang 2 is similar in size and performance to Yuanwang 1. However, unlike Yuanwang 1, which is normally positioned near the Chinese coast, Yuanwang 2 has been positioned in the South Pacific. By 2005 the ship had covered a total distance of 400,000 nautical miles in 31 missions, and was frequently spotted in foreign seaports. During the ShenZhou flight missions, the ship was responsible for commanding the spacecraft to enter its initial orbit after being separated from the launch vehicle.

Yuanwang 3

The 17,000t Yuanwang 3 is the second-generation space tracking ship launched in 1994. It is the most advanced and capable space tracking ship among the Yuanwang fleet. The ship is equipped with an S-band high-accuracy tracking radar as well as sophisticated computer and communications systems to help calculate the re-entry orbit for the spacecraft. During the ShenZhou flight mission, the ship is normally positioned in the South Atlantic off the West African coast. The ship is responsible for the control of the separation of the orbital module and the re-entry module, and the retrofire of the re-entry module at the end of the flight mission. By 2005, the ship had covered a total distance 214,000 nautical miles in 18 missions.
Yuanwang 4

Yuanwang 4 was converted from the ex-ocean survey ship Xiangyanghong 10, which was also constructed in the late 1970s under the Project 718. The ship was converted into a space tracking ship and renamed Yuanwang 4 in 1998, supplementing the existing three Yuanwang space tracking ships to support China’s manned space flight missions. Yuanwang 4 lacks the ability to control the spacecraft, and serves mainly for spacecraft tracking and communications relay roles. The ship is normally positioned in the South Pacific Ocean during a flight mission to rebroadcast the video and audio communications signals between the ShenZhou spacecraft and the mission control centre in Beijing. By 2005, Yuanwang 4 had undertaken 9 missions covering a total distance of 120,000 nautical miles. The ship was damaged in a collusion and fire accident in mid-2007.
Yuanwang 5 and 6

Shanghai-based Jiangnan Shipyard began to build two hulls of the third-generation Yuanwang space tracking ship in 2005. The first hull Yuanwang 5 was launched on 15 September 2006, with the sea trial beginning in early 2007. The ship was officially handed over to the Satellite Maritime Tracking and Control (SMTC) based in Jiangyin on 29 September 2007. The ship will be joined by its sister ship Yuanwang 6 shortly to support China’s Project 921 manned spaceflight and other space missions. Yuanwang 6 was commssioned on 12 April 2008.

Yuanwang 5 has a full displacement of 25,000 tonnes, and is equipped with a whole range of space tracking and communications systems, including an S-band and C-band tracking and control system, and a C-band pulse radar. The ship is capable of tracking space launch vehicles, satellites, manned spacecraft, and other types of spacecraft, as well as real-time voice/image communication and data exchange with the land-based control centre.

Yuanwang 5 features a fibre optics-based shipboard network for data sharing and exchange between different sub-systems onboard. The living conditions for the crew have also been significantly improved compared to previous Yuanwang space tracking ships. According to the Chinese media report, Yuanwang 6 differs from Yuanwang 5 in that it has a large mission control hall occupying two decks. The ship is expected to be commissioned in 2008.
Mission Equipments

The ships are fitted with C- and S-band monopulse tracking radar, Cinetheodolite laser ranging and tracking system, velocimetry system, and onboard computers to track and control the spacecraft. They use a combination of inertial, satellite, and stellar for accurate navigation and positioning. Communications include HF, ULF, UHF, and SATCOM, in the form of secured telephone, radio, fax and data link. The ships are also equipped with a range of weather forecasting equipments including weather radar, sonde, and weather balloon, meteorological satellite image receiving terminal.

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