ESA trusts GMV and DFM to advance the next generation of optical clocks

Today’s EGNOS and Galileo ground infrastructures rely on well-established commercial ground clock technologies (Active Hydrogen Maser, Cesium and Rubidium) that are driving the performance, reliability, and availability of very critical functions in the systems, in particular the continuous generation of the Galileo System Time. These ground clocks are made of complex and non-standard technologies that are only mastered and controlled by a very limited number of suppliers, moreover with complex management of maintenance and obsolescence, as well as overall sustainability of the supply chain in the long term.

Over the last decades, significant progress has been achieved in the science and technologies of new types of atomic clocks demonstrating improved performances, for instance but not limited to, optical clocks. This has resulted in the introduction of new commercial products in the US, or early performance demonstration at prototype level in Europe.

In view of the long time required for the development of such a new critical product in an extremely reduced market, and to the specific programmatic needs of the European GNSS ground infrastructure, a first assessment of European candidate technologies is needed prior to embark into a development of an operational solution, such as an industrial product or alternatives.

GMV and DFM, the Danish National Metrological Institute, have been awarded by ESA a contract to pre-develop an optical clock. The objective of the project is to design and prototype the clock, identifying critical components and securing their supply chain, in order to de-risk the development of a commercial clock at a later stage. 

The proposed optical clock is based on a laser stabilised to a specific transition of the acetylene molecule, using a spectroscopy unit and a feedback control loop. The resulting optical frequency is converted into a standard microwave signal (10 MHz) by means of a frequency comb. Such a clock is expected to provide a stability near the one of a present-day Active Hydrogen Maser.