Atomic Clock Ensemble in Space

The Atomic Clock Ensemble in Space (short: ACES ) is one of the external experimental laboratories that are attached to the Columbus space laboratory, the science lab to ESA for the International Space Station. This purpose, a payload pallet; ACES for the Earth -facing range is provided. It is not to be confused with SolACES, an attempt to measure the influences of VUV radiation.

ACES is used to test a new generation of atomic clocks under the conditions of microgravity. This is a more accurate global time determination ( eg GNSS, in particular Galileo) as well as an evaluation of the theory of relativity are possible.

ACES is only subsequently brought to the International Space Station and will not be from the start with on board, as a number of other experiments also. With the production of the company Astrium is responsible.

The entire unit shall have a mass of 227 kg and an electrical power of 470 W. The test duration is set at 18 months. The launch is currently 2016Vorlage: Future / In 2 years planned aboard an unmanned space freighter ( HTV or Dragon).

Technical details

Core of the experiment is an arrangement of two atomic clocks that work by different methods. Also, the data transmission to Earth to take place via two paths, the one with microwaves, on the other hand a laser path. This run-time effects are to be clarified, the running speed of waves is not constant. An uplink connection is established in the Ku- band, two downlink connections in the S- and Ku- band.

As watches PHARAOH ( Projet d' Horloge Atomique par refroidissement d' en orbite atom ) as a laser- cooled cesium clock (cold Cs- clock) and SHM (Space Hydrogen Maser ) are used as hydrogen maser. The design of Pharaoh was adapted to the previously gained knowledge about influences on atomic clocks in orbit. To this end, a prototype PHARAOH Zero -G experiments were carried out with the A300 ESA, the lead was placed at CNES, the Pharaoh has developed.

Both clocks are synchronized by an internal evaluation tool of ACES, this is called FCDP (Frequency Comparison and Distribution Package). Here also the time signals for the downlink are processed.

Ground stations for experiments

For experiments with ACES a number of ground stations are provided, operate the self- reference clocks of different types:

  • Australia:
  • Brazil:
  • China:
  • Germany:
  • France:
  • United Kingdom:
  • Italy:
  • Japan:
  • Canada:
  • Austria:
  • Russia:
  • Switzerland:
  • USA:

Other external payloads of Columbus

  • European Technology Exposure Facility ( EuTEF )
  • Solar Monitoring Observatory ( SMO / SOLAR )
European Space Agency Micro-g environment Evaluation (disambiguation) H-II Transfer Vehicle Perth Commonwealth Scientific and Industrial Research Organisation Physikalisch-Technische Bundesanstalt Braunschweig OCA National Physical Laboratory (United Kingdom) Mendeleyevo, Moscow Oblast Jet Propulsion Laboratory Pasadena, California SOLAR (ISS) Primary Atomic Reference Clock in Space
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