Ground Environment Test and In-Orbit Performance Verification of Spaceborne Cesium Atomic Clock

Spaceborne cesium atomic clock with magnetic selectors (SCAC) has been used in the global navigation satellite system (GNSS), which can not only improve the positioning accuracy, but also enhance the ability of autonomous operation. So a SCAC product is very favored, but it is very difficult to manufacture. Until November 2019, among the world’s four largest GNSS, only GPS in the U.S. and GLONASS in Russia are equipped with the SCACs. But this situation has been changed now, the first SCAC product in China has been developed by improving its cesium beam tube, frequency standard circuit etc. based on the prototype [1]. The product has been carried on the Beidou navigation satellite and its working state is stable in orbit at present. The analysis results of on-ground and in-orbit data show that the key performance indexes such as frequency accuracy, long-term stability and frequency drift rate could meet the application requirements, and that the product has good space environment adaptability. This paper discusses on the ground environmental test items, methods, conclusions and in-orbit verification related to the product, and summarizes some achievements and experiences in tackling the key technology of the SCAC environmental adaptability, which is very helpful for improving the design ability in space environmental adaptability of atomic clocks.