Atomic Clock Ensemble in Space is a project led by the European Space Agency which will place an ultra-stable atomic clock on the International Space Station. Operation in the microgravity environment of the ISS will provide a stable and accurate time base for different areas of research, including general relativity and string theory tests, time and frequency metrology, and very long baseline interferometry.
The payload actually contains two clocks: a caesium ion clock for long-term stability and a hydrogen maser for short-term stability.
The clock is planned to travel to the space station aboard a Japanese HTV[1], and is to be externally mounted to the ESA's Columbus Laboratory. The clock is planned to operate in orbit for 18–36 months.
Launch is planned in 2013 followed by a 12-18 month operations phase.[2]
Scientific research on the ISS