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

The use of ultra-precise optical clocks\udin space (‘master clocks’) will allow\udfor a range of new applications covering\udthe fields of fundamental physics\ud(tests of Einstein’s theory of General\udRelativity, time and frequency metrology\udby means of the comparison of\uddistant terrestrial clocks), geophysics\ud(mapping of the gravitational potential\udof Earth), and astronomy (providing\udlocal oscillators for radio ranging\udand interferometry in space).\udWithin the ELIPS-3 programme of ESA,\udthe ‘Space Optical Clocks’ (SOC) project\udaims to install and to operate an optical\udlattice clock on the International\udSpace Station (ISS) towards the end\udof this decade, as a natural follow-on\udto the Atomic Clock Ensemble in Space\ud(ACES) mission (which is based on a\udcesium microwave clock), improving\udits performance by at least one order\udof magnitude.\udThe payload is planned to include an\udoptical lattice clock, as well as a frequency\udcomb, a microwave link, and\udan optical link for comparisons of the\udISS clock with ground clocks located in\udseveral countries and continents