We’ve been talking about it for some time now, and now it’s here: the ACES (Atomic Clock Ensemble in Space) mission was launched on Monday 21 April by SpaceX from Cape Canaveral, Florida, bound for the International Space Station (ISS).
This ESA and CNES space mission is carrying several time-measuring instruments, including PHARAO (Projet d’Horloge Atomique par Coolissement d’Atomes en Orbite).
This array will be installed outside the ISS’s Columbus module, in the nadir position, enabling microwave (MWL) and laser (ELT) signals to be transmitted to ground stations equipped with atomic clocks.
This configuration will make it easier to compare space and ground clocks.
This is an unprecedented experiment in fundamental physics! Today, ground-based atomic clocks are so accurate that they only drift by one second every 50 million years. The Pharao clock in question here will only drift by one second in 300 million years. This precision is made possible because the cold atoms of atomic clocks fall freely in space. This makes it easier to measure the second, to carry out numerous tests that will test the theory of general relativity, validate new space technologies and refine global time scales.
The role of LTE and LNE-OP in the mission
LNE-OP, part of the Laboratoire Temps Espace (LTE), plays a key role in this mission. Specialising in time and frequency metrology, it is a key player in the design of atomic fountains, cold caesium atom clocks and new generations of optical clocks, which define the unit of the second with extreme precision.
The LTE has been one of the main contributors to the development of PHARAO. Its teams were involved in defining the clock’s operating principles, setting up experimental protocols to guarantee its accuracy and stability, and carrying out ground tests to validate its performance prior to its integration on the ISS.
The LTE is also responsible for analysing measurements from PHARAO and the microwave link (MWL). Its expertise in signal processing and clock synchronisation will enable it to compare PHARAO with the best terrestrial clocks, in order to refine the measurement of time and explore relativistic effects.
See you in May for the first results!
To find out more, read our article on LTE LI.
En savoir plus sur le site du CNES.
read the CNES press release.
