Space passive hydrogen maser a passive hydrogen maser for space applications

For the passive hydrogen maser (PHM) having excellent frequency stability performance and lower frequency drift, it has been chosen as the one of atomic clock in the Beidou navigation satellite system. Beijing Institute of Radio Metrology and Measurement (BIRMM) is responsible for the whole equipment, including Physics Package (PP) and Electronic Package (EP). A Flight Model (FM) has already launched with satellite. This paper gives the results of PHM physics parameters and measurements of PHM. At last, the paper presents the results of PHM phase comparison on board, and gets negligible drift relative to rubidium clock.