BEIJING — China completed the construction of the BeiDou Navigation Satellite System (BDS) with the launch of its final satellite, the 55th of the BeiDou family, on June 23.

China began to construct the navigation system, named after the Chinese term for the Big Dipper constellation, in the 1990s. It has formulated a three-step strategy for developing the BDS.

The following are some key facts about the construction of the system.

— The construction of BDS-1, the first step of the strategy, started in 1994 and was completed in 2000.

— The BDS-2 system started construction in 2004. By 2012, a total of 14 satellites, including five geostationary earth orbit (GEO) satellites, five inclined geosynchronous earth orbit (IGSO) satellites and four medium earth orbit (MEO) satellites, had been launched to complete the deployment.

— In 2012, the BDS began providing positioning, navigation and timing services to users in the Asia-Pacific region.

— In May 2014, a BDS augmentation system achieved a positioning accuracy of within one meter, a major breakthrough in marine applications.

— In September 2015, China launched the 20th BDS satellite. For the first time, the satellite featured a hydrogen atomic clock. A series of tests related to the clock and a new navigation-signal system were carried out.

— In November 2017, China launched the first two satellites for the BDS-3 system, which started construction in 2009, and officially expanded its regional navigation system into a global network.

— In November 2018, China launched the 41st BDS satellite, also the first GEO satellite of the BDS-3 system, orbiting at about 36,000 km above the Earth.

— By the end of 2018, there were a total of 33 BDS satellites operating in orbit. The navigation system had started to provide global service. The positioning accuracy of the system reached 10 meters globally and five meters in the Asia-Pacific region. Its velocity accuracy was 0.2 meters per second, while its timing accuracy stood at 20 nanoseconds.

— China completed the deployment of the core BDS constellation by sending 10 BDS satellites into space in 2019. The deployment of the core BDS-3 constellation system had been completed with all of the BDS-3 system's MEO satellites being networked.

— On June 23, 2020, China completed the deployment of the whole BeiDou navigation system with the launch of the final BeiDou satellite.