January 27, 2014

CNES’s ultra-precise PHARAO atomic clock in integration at the Toulouse Space Centre

PHARAO is an ultra-precise atomic clock designed to vary by no more than one second in 300 million years. It is set to be used for an exceptional experiment in fundamental physics that will test Albert Einstein’s theory of general relativity. The laser source, a key element of the instrument, will be delivered this week to the Toulouse Space Centre. PHARAO will start operating on the International Space Station in 2016.

The flight model of PHARAO and its associated software are currently being integrated at the Toulouse Space Centre. This phase is scheduled to be completed early in February in time for testing with ultra-cooled atoms to validate the clock’s overall operation. CNES is committed to delivering PHARAO to the European Space Agency (ESA) in the spring of 2014 in readiness for its integration with the ACES payload (Atomic Clock Ensemble in Space). This ensemble is to be launched in May 2016 and attached outside the Columbus module on the International Space Station (ISS).

Any motion has a length and duration. At the start of the 20th century, Albert Einstein’s theories of general and special relativity radically transformed these notions and showed that they depend on the frame of reference in which they are measured and the gravitational potential of the location. For example, time advances more quickly on the ISS than here on Earth, since the station is further from the planet’s centre (theory of general relativity); but it also advances more slowly due to the station’s orbital velocity (theory of special relativity) and it is this second velocity effect, known very precisely from experiments on elementary particles, that prevails. Conversely, the effect of gravitational potential has only been verified to within one ten-thousandth.

The PHARAO laser-cooled atomic clock aims to achieve a precision of one millionth to detect any possible deviation from what the theory of relativity predicts.

CNES is also working on the ACES experiment through its CADMOS centre for the development of microgravity applications and space operations. Once ACES has been attached to the ISS, CADMOS engineers will operate the experiment from Toulouse.

CNES invites you to discover this clock packed with technology currently undergoing clean-room integration in Toulouse.

CNES press contacts
Alain Delrieu Tel. +33 (0)1 44 76 74 04 alain.delrieu@cnes.fr
Julien Watelet Tel. +33 (0)1 44 76 78 37 julien.watelet@cnes.fr