ACES docked with ISS
Above: ACES Production in Friedrichshafen.
Copyright Airbus
ACES is an ESA-led payload developed by Airbus to bring ultra-precise timekeeping to the ISS. It features two cutting-edge atomic clocks that will work together to generate the most accurate time signal ever sent from space. By linking the best clocks on Earth with its own, ACES will test Einstein’s theory of general relativity, improve global time synchronisation and advance our understanding of fundamental physics.
In March, the ACES instrument left the Airbus site in Friedrichshafen, Germany, where it was built and tested, for Florida, from where it has been launched.
The two atomic clocks in ACES’ payload are a laser-cooled Cesium atom clock (PHARAO, made by CNES in France) and an active Space Hydrogen Maser (SHM, made by Safran Timing Technologies in Switzerland). The combined extremely precise (theoretical time deviation of one second in 300 million years) clock signal is sent to the ground via a microwave link.
Eight ground terminals are distributed worldwide allowing ground clock comparison with the payload. The first communication links are expected to occur in only a few days’ time.
The last step now remaining before the start of the mission will require the Canadian Space Agency’s robotic arm to attach ACES to the exterior of ESA’s Columbus laboratory, currently planned for 25th April.
