Atomic Clock Ensemble in Space (ACES)

Atomic Clock Ensemble in Space (ACES) is a fascinating new ESA mission developed in cooperation with the French Space Agency (CNES) that will expand the range of research on the International Space Station (ISS).

The ACES clocks will be installed on the external payload facility of the Columbus module. The frequency reference generated on-board the ISS will be used by a worldwide network of ground terminals to perform comparisons with the best available atomic clocks on the ground.

Time flies on the ISS

Short introductory video of ACES.

The most precise measurement of time yet – in space – will be used to probe our knowledge of the fundamental laws of physics ruling the Universe. ACES will test Einstein’s general relativity and alternative theories of gravitation. Taking full advantage of the microgravity environment and world wide coverage provided by the ISS, ACES will establish a stable and accurate onboard timescale which will be used to perform space-to-ground and ground-to-ground comparisons of best available atomic frequency standards. This is why measuring time as accurately as possible in space is of extreme interest.

The ACES payload will be installed on the external payload facility of the Columbus module. The frequency reference generated on-board the ISS will be used by a worldwide network of ground terminals to perform comparisons with the best available atomic clocks on the ground. For more details please follow the links on the right hand of this page.

Time flies on the ISS

ACES attached to Columbus.

The most precise measurement of time yet – in space – will be used to probe our knowledge of the fundamental laws of physics governing the Universe. ACES will test Einstein’s general relativity and alternative theories of gravitation. Taking full advantage of the microgravity environment and world wide coverage provided by the ISS, ACES will establish a stable and accurate onboard timescale which will be used to perform space-to-ground and ground-to-ground comparisons of best available atomic frequency standards. This is why measuring time as accurately as possible in space is of extreme interest.

Conclusion

The measurement of time has experienced spectacular progress over the last centuries and ACES will provide the next leap forward. Time really does fly on the Internatioanl Space Station.

For more information please contact:

The ACES operational concept
The ACES operational concept

Rosario Nasca
E-mail: Rosario.Nasca@esa.int

In addition, ACES will demonstrate a new type of 'relativistic geodesy' which, based on a precision measurement of the Einstein’s gravitational red-shift, will resolve differences in the Earth gravitational potential at the level of tens of centimetres.

ACES will also contribute to the improvement of the global navigation satellite systems (GNSS) and to their future evolutions; it will perform time transfer and ranging experiments by laser light; it will exploit the GNSS signal for reflectometry measurements and contribute to the monitoring of the Earth atmosphere through radio-occultation experiments.

Interested scientists will be able to procure MWL ground terminals which, connected to the local clock, will allow space-to-ground comparisons with the ACES clock signal.

The ACES users’ community is coordinated by Luigi Cacciapuoti (ESA - Noordwijk) and Christophe Salomon (ENS - Paris).

List of recent publications

  1. L. Cacciapuoti et al., “Atomic Clock Ensemble in Space: Scientific objectives and mission status”, Nucl. Phys. B (Proc. Suppl.) 166, 303 (2007).
  2. C. Salomon, L. Cacciapuoti, and N. Dimarcq, “Atomic Clock Ensemble in Space: Fundamental physics and applications”, Int. Jour. Mod. Phys. D 16, 2511 (2007).
  3. L. Cacciapuoti and C. Salomon, “Cold Atom Clocks in Microgravity: The ACES Mission”, J. Jpn. Soc. Microgravity Appl. 25, 237 (2008).
  4. R. Much et al., “Status of the ACES mission” submitted to EFTF-2009 Conference Proceedings (2009)
  5. E. Daganzo et al., “ACES Ground Segment functionality and preliminary operational concept”, submitted to EFTF-2009 Conference Proceedings (2009).
  6. L. Cacciapuoti and C. Salomon, submitted to Eur. Phys. J. D (2009).

For more information please contact:

Luigi.Cacciapuoti @ esa.int

Last update: 25 October 2011

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