ACES MWL status and test results

Atomic Clock Ensemble in Space (ACES) is a mission using high-performance clocks and links to test fundamental laws of physics in space. The ACES microwave link (MWL) will make the ACES clock signal available to ground laboratories equipped with atomic clocks. The ACES MWL will allow space-to-ground and ground-to-ground comparisons of atomic frequency standards. The MWL comprises the Flight Segment (FS) as part of the ACES payload as well as a distributed set of Ground Terminals (GT), collocated with the ground atomic clocks. MWL is a two-way, two-frequency link transmitting a carrier signal modulated by a PN code, both phase coherent with the local clocks. MWL is designed to reach a time resolution (TDEV) of 0.3 ps in less than 300 s of integration time. In addition to the MWL, operating in microwave domain, ELT is an optical link based on the exchange of laser pulses detected and time stamped in MWL in the local time scale in space and on ground. The engineering model of the MWL FS and the first prototypes of the MWL GT will be used for end-to-end testing of the MWL performance. The end-to-end test is using a set-up, where the MWL FS and GT are connected by cables through a test equipment that allows the full simulation of the signal dynamics during an overflight of the ISS over a MWL GT. The MWL design and test results of the individual elements will be briefly reported. The results of the end-to-end test will be presented and perspectives for clock comparisons with ACES discussed.