Type de publics: Specialist

SPECTROSIM : simulator of the interaction between radiation and a two-levels atom

This software is a computer program whose purpose is to simulate the interaction between radiation and a two-levels atom. For each set of parameters, it gives the curve showing variations of the probability of transition between the two atom levels versus the radiation frequency and an order of magnitude of the frequency
stability. It si mainly dedicated to training (or scientific mediation).

=> Free acces to the program: http://www.first-tf.com/spectrosim/

=> User guide.

26th General Conference on Weights and Measures (CGPM)

The 26th General Conference on Weights and Measures (CGPM) took place in Versailles in November 2018. At this meeting, the CGPM to approved a resolution to revise the definitions of the International System of Units, the SI, which is based on the second, the metre, the kilogram, the ampere, the kelvin, the mole and the candela (the SI base units).
Over the last 50 years, scientists have measured constants of nature, such as the speed of light and the Planck constant, with increasing accuracy; indeed the metre was already redefined back in 1983 in terms of the speed of light. The inherent stability of these constants make them ideal for underpinning new definitions of the SI units and preparing the measurement system to meet the future demands of science and technology.
The SI will be based on seven physical constants, and thus inherently stable. Most notably, this will mark the end of the last remaining physical artefact in the SI system – a cylinder of metal known as the International Prototype of the Kilogram.
The work needed to reach this point has taken many years, and has been a truly international effort. The universality of access that it will afford has been a long-standing goal for the metric system, dating back more than 200 years.
=> More d’information.

The new masters of time

Fifty years ago, on October 13, 1967, marked the first time the second, the unit of time, was defined not by stars but by atoms. In this quest for precision, today’s scientists are now inventing the clocks of tomorrow, which will not only be able to express time with even more accuracy, but may also revisit the fundamental laws of physics.

The economic impact on the UK of a disruption to GNSS

Like all modern economies, much of everyday life in the UK is reliant on Global Navigation Satellite Systems (GNSS). It is sometimes called the invisible utility.

GNSS provide signals from satellites orbiting in space to give us accurate information on positioning, navigation and timing. These systems have a large range of uses but, until now, the economic benefits haven’t always been well understood. It is not clear what the economic impact of a GNSS outage would be on the UK.

This report looks at what would happen to the UK economy if GNSS were unavailable for 5 days.

 

https://www.gov.uk/government/publications/the-economic-impact-on-the-uk-of-a-disruption-to-gnss

The Impact of quantum technologies on the EU’s future policies: Part 1 Quantum Time

Atomic clocks are a quantum technology, used in national metrology laboratories to define UTC and in various networked infrastructure. Developments in the clocks themselves, and in the distribution of precise time, can be expected to affect several application areas of importance to European policy.

https://ec.europa.eu/jrc/en/publication/eur-scientific-and-technical-research-reports/impact-quantum-technologies-eus-future-policies-part-1-quantum-time

Refonte annoncée du Système International d’Unités : enjeux et perspectives

Le système global de mesure qui repose sur le Système International d’Unités (SI) est le cadre actuel assurant la fiabilité et l’exactitude des mesures au niveau international. Un tel système de mesure, transnational et réellement global est indispensable au commerce, à l’industrie et donc développement de nos sociétés modernes. En 2018 le Comité International des Poids et Mesures (CIPM) prévoit de redéfinir le SI. Cette redéfinition consistera principalement à fixer la valeur d’un jeu de constantes fondamentales dimensionnées (la valeur de la constante de Boltzmann kB, par exemple, sera fixée pour redéfinir le kelvin). Cette réforme profonde de notre système de mesure qui reposera sur les meilleures déterminations des constantes fondamentales a pour objectif la mise en place d’un SI plus simple et plus cohérent.

Après un rappel historique sur l’évolution du système d’unités, de la Révolution française à nos jours, nous présentons les enjeux et perspectives de la refonte annoncée du Système International d’Unités.

 

 

 

Les Références de temps et d’espace

Un panorama encyclopédique : histoire, présent et perspectives

Les systèmes de navigations par satellite tels que GPS ou le futur système européen Galileo offrent un éventail impressionnant de possibilités nouvelles aussi bien au grand public qu’aux professionnels (navigateurs, topographes…). L’évolution du niveau des mers est un paramètre-clé du changement climatique, tant pour sa compréhension que pour son impact sociétal. L’exploration planétaire par les missions spatiales produit un nombre croissant de résultats pour la connaissance de notre Système solaire. La vérification et l’amélioration des théories de la gravitation est actuellement une activité importante de la Physique fondamentale.

Un facteur commun est sous-jacent à tous ces constats : le rôle crucial des références de temps et d’espace. C’est l’ambition de cet ouvrage que d’offrir une brève encyclopédie sur ce domaine. Partant d’un panorama historique qui insiste sur l’évolution des concepts, il aboutit à une présentation de l’état actuel, illustrant le rôle majeur des techniques spatiales, et surtout des horloges atomiques qui placent le temps comme élément fondamental sur le plan métrologique.

A Software-Defined GPS and Galileo Receiver

A Single-Frequency Approach

Satellite navigation receivers are used to receive, process, and decode space-based navigation signals, such as those provided by the GPS constellation of satellites. There is an increasing need for a unified open platform that will enable enhanced receiver development and design, as well as cost-effective testing procedures for various applications. This book provide hands-on exploration of new technologies in this rapidly growing field.
One of the unique features of the work is the interactive approach used, giving readers the ability to construct their own Global Navigation Satellite Systems (GNSS) receivers. To construct such a reconfigurable receiver with a wide range of applications, the authors discuss receiver architecture based on software-defined radio (SDR) techniques. The presentation unfolds in a systematic, user-friendly style and goes from the basics to cutting-edge research.