Space mini Passive Hydrogen Maser — A compact Passive Hydrogen Maser for space applications

On-board atomic clocks represent the key technology for the success of any satellite navigation system mission and their development has been continuously supported by ESA. The PHM (Passive Hydrogen Maser) has been selected as master clock of the Galileo Navigation Payload and the almost three years of continuous observation on board of GIOVE-B satellite have confirmed the outstanding performance in terms of frequency stability and negligible drift [1]. The results coming from ground life testing have given important feedbacks on the PHM technology capability to comply with the required 12 years of lifetime. The above was the starting point for the development of a Miniaturized PHM (mPHM) carried out in the frame of the ESA European GNSS Evolutions Programme. The main target was to preserve the excellent PHM frequency stability performance with reduction of the overall mass and instrument sensitivity to the environmental conditions (in particular to temperature). This paper presents an overview of the main results achieved by the design, manufacturing and testing of a MPHM elegant breadboard (EBB); the 30% of mass reduction already achieved on the Physic Package gives the concrete possibility to have a complete instrument with a mass of 12Kg.