Industrialisation approach of the pop atomic clock for application to GNSS

The POP clock is a vapor cell frequency standard operating in pulsed regime at the Rb ground-state hyperfine frequency (6834 MHz). Selex ES´ interest in this technology relies on the possibility to implement a compact unit, with reduced mass, size and power consumption compared to the Passive Hydrogen Maser (PHM, the primary clock of Galileo Navigation Constellation), but similar frequency stability and less operation constraints. A first feasibility study [1] under an ASI contract, was concluded in 2009 with the definition of a preliminary design for space use. Further studies were carried out at INRIM under an ESA contract and with the partnership of Selex-ES (SES). It was demonstrated that the optical detection simplifies the design and improves the frequency stability to values fully compliant to the Galileo specifications for the PHM. This paper presents a summary of the main results achieved by INRIM [2], and the industrialization approach required to pass from the laboratory prototype of the clock to an engineering model designed for the use on navigation satellites. The first step of the development plan will address the realization of electronic and optical units based on commercial components with either space heritage or ability to be space qualified.