PRO Imagery Submittal - ACES

jsc2025e015679 (3/6/2025) --- The closure of the instrument panel of the Atomic Clock Ensemble in Space (ACES) has taken place at Airbus Friedrichshafen, Germany. ACES is an ESA instrument that tests fundamental physics, such as Einstein’s theory of general relativity, from the International Space Station. According to this theory, gravity affects the passing of time—time flies faster at the top of Mount Everest than at sea level. This effect has been proven in experiments on Earth, and ACES will make more precise measurements of this phenomenon and other fundamental physics such as the standard model of particle physics, as it flies 400 km high on the space station. ACES contains two clocks: PHARAO, a caesium atomic clock developed by the French Space Agency CNES, and the Space Hydrogen Maser developed by Spectratime, which uses hydrogen atoms as a frequency reference. The payload will be externally mounted to ESA’s Columbus laboratory on the space station. Image courtesy of S. Corvaja (ESA).