PRO Imagery Submittal - ACES

jsc2025e015681 (3/6/2025) --- The Atomic Clock Ensemble in Space (ACES) facility attached to the exterior of ESA's Columbus facility on the International Space Station. By creating a "network of clocks", this European facility can link its own highly precise timepieces with the most accurate clocks on Earth and compare them to measure the flow of time. ACES includes two cutting-edge clocks: Project d'Horloge Atomique par Refroidissement d'Atomes en Orbit (PHARAO) and Space Hydrogen Maser (SHM). The excellent stability of SHM over a one hour period, combined with the long-term stability and accuracy of PHARAO, provide timekeeping for ACES with a precision of one second over 300 million years. Once in space, a robotic arm positions ACES onto the Columbus module, where it will remain for 30 months to collect data. ACES aims to record continuous data over at least ten sessions of 25 days each. By comparing clocks in space and on Earth, ACES can provide scientists with precise measurements to test Einstein’s gravitational time dilation effect, search for time variations of fundamental constants of physics, and hunt for dark matter. ACES is fully assembled at Airbus in Friedrichshafen, Germany. Image courtesy of D. Ducros (ESA).