The Pharao atomic clock has been delivered to the European Space Agency for testing before its 2016 launch to the ISS

Atomic clock for space station arrives for testing

The Pharao atomic clock, designed to test Einstein's theories, has been delivered to the European Space Agency two years before its departure to the International Space Station. 

The extremely precise atomic clock, built by French space agency CNES, only loses one second in 300 million years. By placing the device on the orbital outpost and linking it with similar clocks on Earth, the scientists will be able to determine whether passing of time is affected by the strength of gravity as proposed by the genius physicist.

Experiments on Earth have proved previously time really passes at different speeds at various altitudes, although the differences are so small they could only be measured by ultra-accurate atomic clocks. Conducting such an experiment with one device placed in the Earth’s orbit would allow for much more telling results, the scientists hope.

Part of the ACES experiment, the Pharao space clock uses lasers to cool caesium atoms down to  –273°C, close to absolute zero. Pharao will be accompanied aboard the ISS by Space Hydrogen Maser, which uses a different technique to keep track of time. This clock uses hydrogen atoms as a frequency reference and offers better stability but for a shorter time.

By coupling the two clocks, ACES will provide the scientists with a unique, highly stable time reference in space.

The space clock will exchange information with atomic clocks in Europe, USA, Japan and Australia through microwave and optical links to create an ‘Internet of Clocks’ and deliver precise timekeeping.

Connecting all these clocks is a significant part of ACES, with France’s Cadmos User Support and Operations Centre taking responsibility for operating the instruments on the Station.

ESA astronaut Thomas Pesquet will be on the orbital outpost when ACES arrives in 2016. Using the Station’s robotic arm, the 375kg payload will be installed on a platform outside Europe’s Columbus space laboratory.

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