- Columbus module with ACES containing PHARAO and Space H-Maser. Credits: ESA – D. Ducros
The International Space Station (ISS) will be the site for an exciting new investigation – probing the principal theories of physics.
The Atomic Clock Ensemble in Space (ACES) is a box-like assembly that will be attached to the outside of Europe’s Columbus laboratory in 2014 for at least for two years on the ISS.
ACES will be the most precise measurement of time yet – in space.
It carries two exquisitely complex high-performance atomic clocks: PHARAO and the Space Hydrogen Maser.
PHARAO stands for Projet d’Horloge Atomique par Refroidissement d’Atomes en Orbite and is a French-built unit that uses laser-cooled cesium atoms.
The other unit is the Swiss Space H-Maser. Together, they will be accurate to about one second over 300 million years.
Why the need for such accuracy?
ACES will test Einstein’s general relativity and alternative theories of gravitation because they attempt to define how time and space are related. This is why measuring time as accurately as possible in space is of extreme interest.
ACES will also benefit metrology – the science of measurement – because highly accurate atomic clocks in space will help in the study of cold-atom physics in microgravity, the comparison of atomic frequency standards, clock synchronization, the realization of a global time scale and contribute to International Atomic Time.
Lastly, ACES will contribute to evolutions of the global navigation satellite network and support the use of precision clocks in major Earth science activities.
The contract for the full development of the ACES payload was recently signed between the European Space Agency (ESA) and the prime contractor, Astrium.
Once ACES is onboard the ISS, any space traveler forgetting his or her traveling alarm clock will have a high-tech back-up!
By LD/CSE