Atomic clocks continuous development at Selex ES for GNSS

On-board atomic clocks represent the key technology for the success of any satellite navigation system mission. The Passive Hydrogen Maser (PHM) has been selected as master clock of the Galileo Navigation Payload and three years of continuous observation on board of GIOVE-B satellite has confirmed the outstanding performance in terms of frequency stability and negligible drift. 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 other Atomic Clocks solutions like POP Rubidium clock and Mini PHM (mPHM). The main target is to preserve the excellent PHM frequency stability performance with a reduction of the overall mass and power consumption. Selex ES have started activities in the area of atomic clocks for navigation back in 2000 with the development of the PHM for Galileo. In 2005 the first qualification model was successfully tested making it possible to fly the first PHM on board GIOVE-B in 2008. Today 32 FM models have been delivered to the Galileo constellation and eight of them are flying on board IOV satellites. This paper presents an overview of the atomic clocks time stability central role in a Navigation Satellite System mission, an overview of POP and mPHM main performances and characteristics, the topics of the Selex-ES industrial approach leading to the industrialization of PHM clocks for space and the establishment the manufacturing and testing facilities at Nerviano premises.