How China’s military exploits its BeiDou PNT satellite constellation

China’s BeiDou constellation of position, navigation and timing satellites is the pride of Beijing’s space programme. Sam Cranny-Evans reports on how the Chinese military uses it.

China’s BeiDou constellation of position, navigation and timing satellites is the pride of Beijing’s space programme. Sam Cranny-Evans reports on how the Chinese military uses it.

In August 2020, the China Satellite Navigation Office announced that the third generation of BeiDou – meaning Big Dipper – position, navigation and timing (PNT) satellites had entered service. The constellation of 30 satellites had been in development since 2009 intending to replace its predecessors, BeiDou 1 and 2, which were completed in 2000 and 2012 respectively.

BeiDou was developed to provide China with an independent source of PNT, removing its reliance on American and Russian systems. The first BeiDou 3 satellite was launched in 2017, and by 2021 more than 40 ground stations had been built to support the operation of the constellation.

Most of the satellites are orbiting in medium earth orbit – 2,000 km to 35,768 km above Earth –however, there are three placed in a highly inclined geosynchronous orbit and three in geostationary positions. This means that six of the satellites are at altitudes above 35,768 km and orbit around the earth’s circumference.

The geosynchronous orbits enable the satellites to return to the same place in the sky at the same time every day, whereas the geostationary orbits would not appear to move at all if viewed from the ground. They are understood to use eight different signals for communications in four different ultra-high frequency bands all between 1,100 Mhz and 1,600 Mhz.

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Positioning accuracy

According to the BeiDou website, the constellation is capable of providing positioning accuracy that is better than 10m, as well as speed measurements to within 0.2 m/s and timing accuracy of less than 20 nanoseconds. Tests by the International GNSS Monitoring and Assessment System showed a global positioning accuracy of 2.34m, the website claims.

BeiDou is about as accurate in civil applications as GPS.

By comparison, the US Global Positioning System (GPS) provides positioning accuracy of around 1.82m, although this can be reduced significantly with dual-frequency receivers. The speed measurement and timing accuracy are similar to those claims put forward by BeiDou, as indicated by the statistics provided by the GPS website. It follows that BeiDou is about as accurate in civil applications as GPS, in the areas that it covers.

The system provides vital independence for China’s armed forces, the People’s Liberation Army, (PLA) and it has proliferated throughout the PLA Ground Force. For military applications, BeiDou is reported to provide a tracking accuracy of 10 cm and can provide the user with data on the status of the satellites.

The primary form of access to BeiDou for the PLA has been through the BeiDou Handheld, which as the name suggests, is a handheld system. It enables the user to determine the position of the system and send text messages up to 1,000 Chinese characters long, provided that the user is in China.

This figure is reduced to 40 characters for global applications. BeiDou also states that it can be used to send voice and pictures within the bandwidth limits of the constellation. Messages sent from a BeiDou handheld are sent to a ground control station by satellite, which sends the message onwards to the receiver.

Battle management

BeiDou is also used to support the PLA’s battle management system, which, at the brigade level, provides a commander with awareness of unit positions, attrition, and combat results. The value that this provides to the PLA’s armoured formations is that it enables commanders to gain an awareness of where their units are on the battlefield.

This improves situational awareness and the ability of commanders to coordinate combined arms effects in their operational environment. BeiDou is understood to be used in a vehicle-mounted configuration for this role.

The handhelds provide other benefits for the PLA’s Ground Force. One exercise from mid-January used them to provide the locations of battle-damaged vehicles to a brigade commander. The timely provision of data enabled a rapid response and improved the brigade's performance during the exercise, according to an article in the PLA Daily.

Separate PLA exercise reports state that it can be used to mark target coordinates by a reconnaissance platoon; they were then engaged by snipers within the platoon. It may be possible for those coordinates to be shared with other long-range strike assets.

//  BeiDou constellation satellites use medium earth orbit, an inclined geosynchronous orbit and geostationary positions. Credit: BeiDou programme

Border defence

The BeiDou handheld has also gained popularity among China’s border defence regiments, which often operate in communications dead zones, according to one China Military Network report from 2015. BeiDou is used to communicate with the command centres of border defence regiments located in mountainous terrain, where communicating via conventional line of sight radios may not be possible all of the time.

The same publication reported in 2019 on a remote border patrol, which used the BeiDou handheld as a form of battle management system, which allowed the patrol’s command post to track its movements. The handheld BeiDou can be paired with other dedicated communications vehicles, which can include the ability to transmit voice, text and video footage via satellite. It is even used for navigation by the cavalry company of the PLA Rocket Force, which patrols China’s mountainous frontiers on horseback to protect the country’s strategic deterrent.

Other applications have included a mobile emergency command platform for the city of Dezhou, which includes BeiDou for PNT functions, satellite communication and 3/4G functions. The system was designed to ensure that the city could communicate with higher levels of command in times of peace when responding to natural disasters, such as flooding, and in war. It was developed by the PLA and civilian companies, the Chinese Ministry of National Defence said, and enabled full-motion video to be transmitted from anywhere in the city.

Although the BeiDou only reached its full operational capability with the positioning of the final satellite in 2020, it is clear that the constellation has become a core element of the PLA’s operations. It supports multiple mission functions, and given the PLA’s ambitions to become an integrated, all domain force, its importance will only grow.

// Main image: Precision oscillators using quantum clocks would improve overall radar performance. Credit: Petair. Shutterstock