Towards Neutral-atom Space Optical Clocks (SOC2): Development of high-performance transportable and breadboard optical clocks and advanced subsystems

The use of ultra-precise optical clocks in space (‘master clocks’) will allow for a range of new applications covering the fields of fundamental physics (tests of Einstein’s theory of General Relativity, time and frequency metrology by means of the comparison of distant terrestrial clocks), geophysics (mapping of the gravitational potential of Earth), and astronomy (providing local oscillators for radio ranging and interferometry in space). Within the ELIPS-3 programme of ESA, the ‘Space Optical Clocks’ (SOC) project aims to install and to operate an optical lattice clock on the International Space Station (ISS) towards the end of this decade, as a natural follow-on to the Atomic Clock Ensemble in Space (ACES) mission (which is based on a cesium microwave clock), improving its performance by at least one order of magnitude. The payload is planned to include an optical lattice clock, as well as a frequency comb, a microwave link, and an optical link for comparisons of the ISS clock with ground clocks located in several countries and continents.