China launched the final pair of spare satellites for its Beidou navigation system late Wednesday, indicating that the system could be upgraded in the future. The Long March 3B rocket equipped with the Yuanzheng-1 upper stage lifted off from the Xichang Satellite Launch Center at 21:14 on September 18 (0114 UTC on September 19). The two spare Beidou Positioning, Navigation, and Timing (PNT) satellites were successfully launched into Medium Earth Orbits (MEO).

These satellites are the 59th and 60th satellites launched for China’s Beidou Global Navigation Satellite System (GNSS). The new satellites were provided by the Innovation Institute of Microsatellites at the Chinese Academy of Sciences (IAMCAS). The China Academy of Space Technology (CAST) also designed and manufactured the Beidou satellites.

The new pair will join the existing Beidou MEO orbital aircraft as backups, enabling maintenance and control of the satellites while maintaining full operation of the system.

In addition, the duo will also conduct experiments for the future Beidou-4 next-generation navigation satellite technology, which includes improvements over previous Beidou satellites in areas such as autonomous integrity monitoring and atomic clock technology.

“The two satellites represent the final group of Beidou-3 and serve as a bridge between the current and future generations. In addition to carrying out their normal duties as constellation satellites, they will also take part in technical survey and exploration projects,” Liu Yingchun, chief designer of the Beidou-3 system, told CCTV.

Beidou-3 belongs to the global phase of Beidou’s three-phase program, which began with Beidou-1 and Beidou-2 satellites providing regional positioning services. The system has 24 satellites in MEO, eight in each plane excluding backups. In addition, there are three Beidou satellites in inclined geosynchronous orbits and three satellites in geostationary orbits. Beidou is used for both military and civilian purposes.

Beidou-4 represents planned modernization. China aims to establish a more widespread, integrated and intelligent comprehensive PNT system by 2035. Although details are scarce, Beidou-4 will address technical challenges such as weak satellite navigation signals and interference, and aim to support underwater, closed-space and deep-space navigation.

According to the Belfer Center report, Beidou and its supporting ground infrastructure provide the most accessible and accurate PNT data of active GNSS constellations in some regions, including the US Global Positioning System (GPS).

Meanwhile, a report from the Government Accountability Office (GAO) released earlier this month revealed that the U.S. Space Force is facing technical hurdles in developing the next generation of GPS satellites and ground systems.

The launch was the 41st for China in 2024. It came after a two-week hiatus in Chinese launches following the automaker’s Sept. 6 Long March launch that sent 10 Geely satellites into orbit for its “Future Mobility Constellation.”

Prime contractor CASC said earlier this year it planned to conduct about 70 launches by 2024. Another 30 launches were planned by commercial participants, but only six have been completed so far. The Kuaizhou-1A (Expace) and Lijian-1 (CAS Space) solid-state rockets and other Long March launches are expected to launch next week. The new Long March 12 launcher is expected to be introduced from the new commercial panel in the near future. In early September, the region was hit by Typhoon Yagi, which affected launch infrastructure.