News & Events
Probing space-time by combining cold atom clocks, laser pulses and a satellite
Launched in June this year and running until September, a major time comparison experiment is being conducted with two very-high-precision clocks located some 800 km apart, at the Observatoire de Paris and the Observatoire de la Côte d’Azur (OCA) in the South of France. The technique used, called T2L2, developed by OCA, involves time transfer by laser link via Jason-2, an oceanographic satellite orbiting the Earth at an altitude of 1336 km.
As Jason-2 passes above the two observatories each day, their physicists fire laser pulses simultaneously towards the satellite. Pulses lasting 10 picoseconds (one hundred-billionth of a second) are emitted 10 times per second for a period of around 10 minutes. Jason-2 sends the signal back to each laser station. These events are recorded by the clocks on the ground and other clocks aboard the satellite.
By using lasers in conjunction with cold atom clocks, the researchers hope to obtain a much lower noise level and much higher accuracy than is possible using time comparison techniques based on microwave links (GNSS, TWSTFT). The experiment is difficult to perform, however, as it is not possible to use lasers in cloudy weather conditions. A cloud crossing the trajectory of the laser beam generates noise and greatly weakens the signal.
Apart from improving our knowledge and performance in the field of time comparison, the experiment aims to push back the frontiers of scientific theories such as Einstein's theory of general relativity.
The T2L2 experiment calls on the expertise of three partner laboratories: the National Space Research Centre (CNES), the National Scientific Research Centre (CNRS), and the National Metrology and Testing Laboratory (LNE-SYRTE).
Click here for an explanation of the experiment on French radio.
French metrology researchers to make key contribution to CPEM 2010
The 27th Conference on Precision Electromagnetic Measurements (CPEM 2010) is taking place in South Korea from 13 to 18 June. Researchers from the French metrology network will be making over 30 contributions, presenting their research work in oral and poster presentations and chairing several sessions.
The topics presented by the French metrology network will address one of the main themes of the conference, the redefinition of SI units. The researchers will explain the progress they have made in their work on:
- the metrological triangle and the calculable standard of capacitance, for a new definition of the ampere
- the Boltzmann constant, for a new definition of the kelvin
- the watt balance, for a new definition of the kilogram (in collaboration)
- clocks, in the field of optical and microwave frequencies (LNE-SYRTE).
LNE will detail its recent research in the field of quantum electrical metrology, in particular the characterization of graphene for implementation of the quantum Hall effect, and the Josephson effect in AC. Other current research fields to be presented will include nanometrology (development of an atomic force microscope), high-frequency bolometric mounts, and energy.
LNE-CNAM will also present its work on long distance measurement.
The full conference programme is available on the CPEM website.
EMRP: €200 million contract signed with the European Commission
The European Metrology Research Programme (EMRP) is going ahead. Following the adoption of Article 169/EMRP by the European Parliament in May 2009 and approval by the Council of Ministers two months later, a €200 million contract with the European Commission was signed by EURAMET president Leslie Pendrill (SP, Sweden) and EMRP president Luc Erard (LNE, France) on 27 November 2009.
This financing will enable Europe's national metrology institutes to integrate and expand their research programmes in the priority fields specified in the EMRP. The French metrology network will be playing an active role and expects to obtain up to €20 million in support over seven years.
The European Commission had already provided a €17 million budget in 2009, enabling a first call for projects in the field of energy to be launched in advance. After specification of themes followed by a two-stage selection process, nine joint research projects (JRPs) were selected. The French metrology network will contribute to eight of them and will run the JRP on metrology for biofuels.
