Space clock to boost positioning accuracy of China’s satellite systems
Global Times

The world's first space cold atom clock (CAC) is expected to drive the accuracy of global navigation satellite systems to another level, expert said after the clock passed all tests in the Tiangong-2 space lab.

The new technology can reach a stability of 7.2×10-16, which means an error of within "one second every 30 million years," Liu Liang, leader of the project, told the Global Times on Thursday.

An ordinary quartz clock is accurate to some seconds every 10 days, while mechanical watches could err several seconds in a day, according to Liu.   

The Tiangong-2 was launched in 2016. Testing the CAC was one of the 14 research programs conducted in the space lab during the past two years, according to a report released by the Chinese Academy of Sciences. 

The results were published in the journal Nature Communication on Tuesday. 

CAC uses laser-cooled atoms as a medium to receive highly stable frequency signals, while traditional atomic clocks use hot atoms which have almost reached their limits, especially in regard to long-term stability, Liu said.

Such clocks operating in outer space can "overcome the gravity which causes timing errors on earth," Jiao Weixin, a space science professor at Peking University said.

The atomic clock is the core of a navigation satellite system. An improvement of an atomic clock's performance can improve not only the positioning accuracy, but also the stability of the system, Liu said. 

 "We hope CAC could be applied to navigation satellite systems in the near future, where the navigation accuracy could be raised to another level…which can also be expected to help improve [China's] military capability," Liu said.

Cover image: CCTV