China Maritime Satellite Telemetry and Control Department

The China Maritime Satellite Tracking and Control Department ), MUCD 63680, is a corps deputy grade naval base located at Jiangyin City in Jiangsu Province, established in 1978 as the headquarter and home port for the Yuan Wang-class tracking ships, which are used to track rocket and missile launches, in particular the testing of the Dongfeng series ballistic missiles and Long March rockets. Since 1 January 2016, it has been subordinate to the Main Department of Satellite Launches and Orbit Tracking and Control (卫星发射测控系统部) of the Strategic Support Force, and then from April 2024, of the Aerospace Force.

History
The decision to create a tracking and control fleet started with a suggestion in 1965 by Qian Xuesen that intended to help with the development of the Dongfeng-5 ICBM. On July 18, 1967, the project was officially launched under the umbrella of the then State Commission for Science and Technology and, as was customary in China, named after the date: "Project 718" (718工程, pinyin: 718 Gōngchéng). In April 1975, a command staff was established in Jiangyin on the lower reaches of the Yangtze River to prepare for the construction of a military base. At the same time, the Jiangnan shipyard on the island of Changxing near Shanghai began the construction of two tracking ships, the Yuan Wang 1 and the Yuan Wang 2 (远望一号 and 远望二号 respectively) , which were launched on August 31 and October 1977 respectively. The two ships were identical in construction, with a length of 191 m, a width of 22.6 m, a draft of 9 m and a standard displacement of 21,000 tons.

Jiangyin Naval Base was designated as the "23rd Base", and in October 1978, the "Chinese People's Liberation Army Base for Testing and Training" officially went into operation. However, the two tracking ships still had to go through a whole series of tests on the high seas, and the direction-finding devices had to be installed. They were not put into service until the beginning of 1980.

The delay in construction was partly due to the fact that the ships had been built during the Cultural Revolution, when disruption was generalized. The ships also had some severe defects that needed correction. In addition to the antennas for tracking and controlling the rockets and satellites, the ships also had a powerful transmitter on board for transmitting data to the headquarters of the Chinese space control network in Weinan. It turned out that as soon as this transmitter was put into operation, it interfered with the other devices on the ship so much that they were no longer operational. An attempt to first transmit the data with a weak transmitter to the sister ship a few dozen kilometers away, which then relayed it to the mainland at full power, could not solve the problem. Finally, Chen Fangyun's engineers designed a frequency distribution scheme in which the radio and USB frequencies were chosen so that interference no longer occurred.

Early missions
The then "Unit 89001" had its first major mission in May 1980 during the first long-range flight test of the Dongfeng 5. At the end of April, the two Yuan Wang ships met at the Zhoushan Islands off the coast of Zhejiang, with a total of 16 ships selected from the Eastern Sea Fleet, the Northern Sea Fleet, the Southern Sea Fleet, and the Research Fleet of the State Oceanic Administration, plus 4 helicopters and sailed more than 8000 km to a sea area northeast of Australia, where they took up a square, 32 × 32 nautical miles formation. Installed on the Yuan Wang 1 was the "Computer 151" developed by the Changsha Polytechnic Academy, China's first MegaFLOP-supercomputer. The ship acquired the missile's bearing signal, and the computer calculated its path relative to the ship's position in real time, allowing radar and laser range finders to precisely track its ballistic route, and allowed the helicopters to be guided to the expected impact site. The intercontinental ballistic missile launched on May 18 at 10:00 local time from Jiuquan Space Launch Center hit exactly in the middle of the target square, and less than two minutes later it had been taken by the helicopters out of the water. The Yuan Wang ships played an important role, as well as on September 15 and 27, 1988, in tests of the medium-range JL-1 missiles fired from the submerged Changzheng 6, the only nuclear submarine of the 09II class.

On September 21, 1992, the Politburo Standing Committee of the Chinese Communist Party approved the manned space program, named after the date as "Project 921" (921工程, pinyin 921 Gōngchéng). With the stakes higher, a third tracking ship was laid down, the Yuan Wang 3, which was launched on April 26, 1994, and, after extensive testing, on May 18 was put into service in 1995. From August 1998, the oceanographic research ship Xiang Yang Hong 10 (向阳红10号) was converted into a tracking ship at the Chengxi repair yard in Jiangyin and delivered to the Xi'an Satellite Control Center on July 18, 1999, as "Yuan Wang 4".

On December 2, 1994, the Yuan Wang 2 showed what these ships were capable of. The last stage of the Changzheng-3A rocket failed, and the communications satellite Dong Fang Hong 3-1, launched on November 30, 1994, was stuck in lower orbit. The tracking ship then radioed the satellite to fire its own engine. The power of the engine was not sufficient, and the satellite only reached a subgeostationary orbit and had to be abandoned. Nevertheless, this was the first time China had performed remote maintenance on a satellite. Following this success, the Xi'an Satellite Control Center, the superior office of Jiangyin, broadcast the launch of the telecommunications satellite Dong Fang Hong 3-2 on May 12, 1997, and the weather satellite Fengyun 2. With the spin-stabilized weather satellite, the crew of Yuan Wang 2 managed to simultaneously adjust attitude and nutation, a technique that had been used until then only by Russia and the USA.

Manned space program
The visibility of the Jiangyin base to the Chinese public soared after the launch of the test spacecraft for the manned space flight program, later named "Shenzhou 1," on November 20, 1999. All four tracking ships had sailed and were spread across the Atlantic, Pacific and Indian Oceans (the ground stations in Swakopmund, Karachi and elsewhere did not yet exist at that time). When, after 14 orbits around the Earth, the spacecraft ignored the command sent by the Beijing Space Operations Center to re-enter the atmosphere on the second attempt, it was the Yuan Wang 3 lying off the coast of Namibia that, after the crew had located the spacecraft, successfully gave the order to initiate the braking maneuver. 9 minutes later, the spacecraft had left the radio range of the Yuan Wang 3, independently crossed Africa and Pakistan until it finally entered Chinese airspace over Tibet and landed in Inner Mongolia. On January 4, 2000, the last of the tracking ships returned to Jiangyin. During the mission, which lasted a total of 259 days, the four ships covered a total of 185,000 km.

In October/November 2007, the Yuan Wang 2 and Yuan Wang 3 took part in the Chang'e-1 mission, both tracking and sending control commands, including entering the probe into lunar orbit. This extended the tracking ships' working range from 70,000 km, geocentric Earth orbits, to 400,000 km, and made the Jiangyin fleet become an integral part of the Chinese Deep Space Network.

Equipment
The orbit tracking ships are each equipped with three movable parabolic antennas, which can work like a single large dish via interferometry and are then mainly used for tracking rockets after launch and for satellites at low and medium altitudes (less than 2000 km or between 2000 km and 36,000 km) and in geostationary (35,786 km) orbits. The tracking ships work on the S and C bands of the microwave range. In order to increase the measurement accuracy, the track tracking ships are equipped with fin stabilizers, which monitor the rolling of the ship in wind and sea conditions, for example in the Yuan Wang 5 can reduce her rolling from 15 ° to 5°. In the base of the parabolic antennas there are other devices that reduce the swaying from 5° to 1°, and on the antennas themselves there is a device that reduces the swaying from 1° to a few angular seconds. This means that the dishes are stable up to wave strength 6 (4 – 6 m high waves), almost as stable as at a ground station. Up to wind force 12, i.e. wind speeds of 118 – 133 km/h, the antenna can remain pointed horizontally towards the sky.

The newer orbit tracking ships have a crew of around 400 men and women who are responsible for the nautical systems of the ship itself, the orbit tracking and control of the spacecraft, telecommunications and meteorology. The drinking and service water for the crew is not carried along, but is processed from seawater during the journey using reverse osmosis. After every mission, a tracking ship stays at the Jiangyin base for at least a month, where all systems are checked and the crew practices for the next mission after a rest period. On average, all four tracking ships together spend about 600 days per year at sea.

Rocket transports
Since heavy rockets of the type Changzheng 5 and Changzheng 7, which have been under construction since 2009 in Tianjin, could only be delivered by sea (as could their intended heavy payloads) it was necessary to build specialized freighters. The problem here was that rockets are very sensitive. In order to be able to maintain the prescribed limit conditions of 5-25 °C and less than 60% humidity in the inside of the transport containers, there are strict requirements for temperature, humidity and the salinity of the air in the cargo hold, as well as requirements for the loading and unloading speed, so that the rockets are not subjected to maritime climate for an unnecessarily long time in either Tianjin or Hainan For this reason, the engineers at the Civil Ship Department of the Research Institute 708 (第七〇八研究所民船部) of the China State Shipbuilding Corporation designed the holds of the Yuan Wang 21 and her sister ship Yuan Wang 22 as closed, fully air-conditioned rooms in which the rocket stages packed in transport containers are stored in such a way that vibrations are dampened and the ship's fluctuations caused by the waves are compensated for.

In heavy seas, ships without fin stabilizers can tilt up to 40° from the center axis, which can mean lateral accelerations of up to 0.8 g, while the load on a freight train or truck going through a curve is only exposed to 0.5 g. However, thanks to the special design, these load values for the rocket freighters are only half compared to road transport and only a third compared to rail transport. Thanks to the fin stabilizers, the rocket freighters can operate in wave heights of up to 2.5 m. When there are predicted wave heights of over 2.5 m, the risk to the valuable cargo becomes too high. In such a case, such as during the transport of the third Changzheng-5 launch vehicle from Tianjin to Hainan (October 22–27, 2019), the regulations required the freighters to anchor in a wind-protected anchorage and wait for better weather.

The two rocket freighters were built from April 1, 2012, by the Jiangnan Shipyard in Shanghai. On November 29, 2012, the Yuan Wang 21 and then the YW 22 were launched, After installing the electronic equipment and testing at sea, the Yuan Wang 21 was handed over to the Jiangyin Tracking Ship Base on May 6, 2013, the Yuan Wang 22 on June 28, 2013. The Yuan Wang 21 had its first actual use two years later. On May 14, 2016, after a six-day, 1,670 nautical mile voyage, the freighter delivered a Changzheng 7 carrier rocket to the port of the Wenchang Launch Site, from where the rocket was delivered on June 25, 2016, at 12: 00 UTC, and then completed its first flight without any problems.

With a length of 130 m and a standard displacement of almost 10,000 t, the freighters are relatively small; in order to be able to transport the components of a heavy Changzheng-5 launch vehicle with the associated boosters, it needs to be broken down to 40 containers, some of which are over 30 m long, and both ships have to leave the port at the same time for one rocket. This is related to the situation at Qinglan port on Hainan. The rocket wharf is located around 2 km inside the island and therefore offers protection from tropical storms up to wind force 10 (89 – 102 km/h; the summer typhoons on the Eastern Hainan coast reach wind speeds of over 200 km/h). However, the shipping channels designated for deep-sea freighters (7.3m deep) are very narrow: 64 m for the entrance to the harbor itself, 60 m for the entrance to the particularly wind-protected Bamen Bay. For comparison, in Jiangyin, the Yangtze is open to heavy shipping traffic over a width of 600 m. Therefore, For safety reasons, the base refrained from building freighters large enough that one alone could transport a Changzheng-5 rocket.

For the transport of a Changzheng 5B launch vehicle in February 2021, which was supposed to carry the Core Module of the Chinese Space Station into space, the Xu Yang 16 (绪扬16号) was used, a multi-purpose ship of the Ningbo Xuyang Shipping Ltd. (宁波绪扬海运有限公司) launched in January 2009 with a Standard displacement of 10,134 t, 125 m length, 19 m width and up to 7.6 m draft. Unfueled rocket stages are relatively light, so the real draft was still within limits.

Organization
The department has the following subordinate units.
 * Experimental Engineering Department (试验技术部)
 * Yuan Wang-3 (远望三号): Oceanic tracking and command ship
 * Yuan Wang-5 (远望五号): Oceanic tracking and command ship
 * Yuan Wang-6 (远望六号): Oceanic tracking and command ship
 * Yuan Wang-7 (远望七号): Oceanic Tracking and Command Ship
 * Yuan Wang-21 (远望二十一号): Rocket Transport Ship
 * Yuan Wang-22 (远望二十二号): Rocket Transport Ship
 * First Group of Tracking Ship Crew (航天远洋测量船船员第一大队)
 * Second Group of Tracking Ship Crew (航天远洋测量船船员第二大队)