Atomic clock ensemble in space

The Atomic Clock Ensemble in Space (ACES) mission is developing high clocks and links for space to test Einstein's theory of general. From the International Space Station, the ACES payload will a clock signal with fractional frequency stability and accuracy of1E-16 establishing a worldwide network to compare clocks in space and on the. ACES will provide an absolute measurement of Einstein's gravitational, it will search for time variations of fundamental constants, to test topological dark matter models, and perform Standard Model tests. Moreover, the ground clocks connected to the ACES network will compared over different continents and used to measure geopotential at the clock locations. After solving some technical problems, the flight model is now approaching its completion. System tests involving the-cooled Cs clock PHARAO, the active H-maser SHM and the on-board frequency FCDP have measured the performance of the clock signal delivered by. The ACES microwave link MWL is currently under test. The single-photon detector of the optical link ELT has been tested and will now be in the ACES payload. The ACES mission concept, its scientific, and the recent test results are discussed here together with the milestones that will lead us to the ACES launch.