BEIJING, Jan. 18 (Xinhua) -- China leads development of satellite atomic clocks, researchers said Thursday.

BeiDou navigation satellites sent to orbit last week are fitted with the latest generation of rubidium and hydrogen atomic clocks developed by the Second Academy of China Aerospace Science and Industry Corp.

Compared with the previous generation, the new clocks are smaller, lighter, perform much better and are among the world's best, Chinese scientists said.

Atomic clocks use vibrations of atoms to measure time. An accurate and ultra-stable set of atomic clocks is essential for global navigation satellite systems that require a high degree of precision.

BeiDou aims to rival the GPS of the United States, European Union's Galileo as an alternative global satellite navigation system. It intends to cover Belt and Road countries by the end of 2018 and operate globally by around 2020 with a 35-satellite constellation.