China declared the official commissioning of the BeiDou Navigation Satellite System (BDS) on Friday, marking the formal launch of the newly completed BDS-3 system for global users.

The BDS system involves efforts of more than 400 agencies and 300,000 research personnel and technicians. The China Academy of Space Technology (CAST), developer of the satellites, has gathered leading experts and manufacturers from around the country, and integrated the most advanced technologies and high-quality materials and products for the program.

INDEPENDENTLY-DEVELOPED "HEART"

Under the mechanism, the Xi'an branch of the CAST undertook the development of rubidium atomic clocks.

Dubbed the "heart" of the navigation system, rubidium atomic clocks provide time and frequency standards for BDS satellites, and are key to the system's positioning, speed measurement, and timing accuracy.

In the past two decades, the Xi'an branch has delivered more than 100 rubidium atomic clocks, including 70 high-precision rubidium clocks, to the BDS program.

China started to develop atomic clocks as early as the 1960s and 1970s. However, most of the research at that time was theoretical and ground-based.

As China decided to build its own satellite navigation system, self-developed rubidium atomic clocks proved to be of great significance to the autonomous control of the whole system.

The Xi'an branch developed the first rubidium atomic clock between 1996 and 2000, but there was still a long way to go before it could work in space since the clock had to stand the test of the vacuum environment, the impact of the launch, and long-term irradiation.

In order to overcome the challenges in developing rubidium atomic clocks for space, younger members of the research team spent day and night in the lab and worked around the clock to carry out experiments.

"I was touched by their dedication," said Lei Wenqi, a former leader of the rubidium atomic clock project at the Xi'an branch.

China's first self-developed rubidium clock was successfully tested on a satellite in 2006. Since 2012, China's self-developed rubidium clocks have fully replaced imported rubidium clocks in some of the BDS-2 satellites. In 2016, the Xi'an branch was capable of producing up to 50 satellite rubidium clocks per year.

"In the future, our goal is to enhance the performance of rubidium clocks, and improve their daily timing accuracy from one billionth of a second to one 10-billionth of a second," Lei said.

UPGRADED SERVICES

Along with positioning, navigation, and timing services, the BDS-3 system can also provide a variety of value-added services like global search and rescue, short message communication, ground-based and satellite-based augmentation, as well as precise point positioning.

The BDS-3 can accurately locate trapped ships and personnel, thereby contributing to international rescue efforts.

The BDS-2 satellites have also been equipped with payloads of short message communication.

In 2008, when a magnitude-8 earthquake struck Wenchuan in southwest China's Sichuan Province, severely damaging ground communication facilities, rescuers used the short message function of BDS-2 to report the locations of the quake-hit areas.

Different from the BDS-2, the BDS-3 expanded the service area of the short message function from the Asia-Pacific region to the entire world.

The regional short message communication capabilities of the BDS-3 has been improved nearly 10 times, while the capacity globally reaches 40 Chinese characters.

These features endow the BDS-3 with great application prospects. China has developed a variety of BeiDou terminal products for disaster relief vehicles and personnel, supporting direct disaster reporting, vehicle navigation monitoring, and emergency rescue.

Meanwhile, the BDS-3 system has also helped farmers free their hands via autonomous driving, high-precision positioning and navigation, and other emerging technologies.

The BDS-based agricultural machinery management system, developed by Space Star technology CO., Ltd., offers operation supervision, real-time tracking, track playback, as well as emergency command and dispatching of agricultural machinery in agriculture production.

This has been applied in Heilongjiang Province, Xinjiang Uygur Autonomous Region, Inner Mongolia Autonomous Region, and other provincial-level regions. More than 20,000 BDS agricultural machinery terminals have been sold.