Atomic clocks: new prospects in metrology and geodesy

We present the latest developments in the field of atomic clocks and their applications in metrology and fundamental physics. In the light of recent advents in the accuracy of optical clocks, we present an introduction to the relativistic modelization of frequency transfer and a detailed review of chronometric geodesy.Comment: Proceedings of the Workshop "Relativistic Positioning Systems and their Scientific Applications" held in Brdo near Kranj, Slovenia, 19-21 September 2012. To appear in Acta Futura (http://www.esa.int/gsp/ACT/publications/ActaFutura/

An Autonomous Reference Frame for Relativistic GNSS

Current GNSS systems rely on global reference frames which are fixed to the Earth (via the ground stations) so their precision and stability in time are limited by our knowledge of the Earth dynamics. These drawbacks could be avoided by giving to the constellation of satellites the possibility of constituting by itself a primary and autonomous positioning system, without any a priori realization of a terrestrial reference frame. Our work shows that it is possible to construct such a system, an Autonomous Basis of Coordinates, via emission coordinates. Here we present the idea of the Autonomous Basis of Coordinates and its implementation in the perturbed space-time of Earth, where the motion of satellites, light propagation, and gravitational perturbations are treated in the formalism of general relativity.Comment: 5 pages, 3 figures, in proceedings of the 4th International Colloquium: Scientific and Fundamental Aspects of the Galileo Programme, 4-6 December 2013, Prague, Czech Republic; removed unnecessary indices from eqs. 3,6,7 and corrected minus signs in eqs. 6 and

Astrophysics datamining in the classroom: Exploring real data with new software tools and robotic telescopes

Within the efforts to bring frontline interactive astrophysics and astronomy to the classroom, the Hands on Universe (HOU) developed a set of exercises and platform using real data obtained by some of the most advanced ground and space observatories. The backbone of this endeavour is a new free software Web tool - Such a Lovely Software for Astronomy based on Image J (Salsa J). It is student-friendly and developed specifically for the HOU project and targets middle and high schools. It allows students to display, analyze, and explore professionally obtained astronomical images, while learning concepts on gravitational dynamics, kinematics, nuclear fusion, electromagnetism. The continuous evolving set of exercises and tutorials is being completed with real (professionally obtained) data to download and detailed tutorials. The flexibility of the Salsa J platform tool enables students and teachers to extend the exercises with their own observations. The software developed for the HOU program has been designed to be a multi-platform, multi-lingual experience for image manipulation and analysis in the classroom. Its design enables easy implementation of new facilities (extensions and plugins), minimal in-situ maintenance and flexibility for exercise plugin. Here, we describe some of the most advanced exercises about astrophysics in the classroom, addressing particular examples on gravitational dynamics, concepts currently introduced in most sciences curricula in middle and high schools.Comment: 10 pages, 12 images, submitted to the special theme issue Using Astronomy and Space Science Research in Physics Courses of the American Journal of Physic

Extended Fermi coordinates

We extend the notion of Fermi coordinates to a generalized definition in which the highest orders are described by arbitrary functions. From this definition rises a formalism that naturally gives coordinate transformation formulae. Some examples are developped in which the extended Fermi coordinates simplify the metric components.Comment: 16 pages, 1 figur

GENESIS: Co-location of Geodetic Techniques in Space

Improving and homogenizing time and space reference systems on Earth and, more directly, realizing the Terrestrial Reference Frame (TRF) with an accuracy of 1mm and a long-term stability of 0.1mm/year are relevant for many scientific and societal endeavors. The knowledge of the TRF is fundamental for Earth and navigation sciences. For instance, quantifying sea level change strongly depends on an accurate determination of the geocenter motion but also of the positions of continental and island reference stations, as well as the ground stations of tracking networks. Also, numerous applications in geophysics require absolute millimeter precision from the reference frame, as for example monitoring tectonic motion or crustal deformation for predicting natural hazards. The TRF accuracy to be achieved represents the consensus of various authorities which has enunciated geodesy requirements for Earth sciences. Today we are still far from these ambitious accuracy and stability goals for the realization of the TRF. However, a combination and co-location of all four space geodetic techniques on one satellite platform can significantly contribute to achieving these goals. This is the purpose of the GENESIS mission, proposed as a component of the FutureNAV program of the European Space Agency. The GENESIS platform will be a dynamic space geodetic observatory carrying all the geodetic instruments referenced to one another through carefully calibrated space ties. The co-location of the techniques in space will solve the inconsistencies and biases between the different geodetic techniques in order to reach the TRF accuracy and stability goals endorsed by the various international authorities and the scientific community. The purpose of this white paper is to review the state-of-the-art and explain the benefits of the GENESIS mission in Earth sciences, navigation sciences and metrology.Comment: 31 pages, 9 figures, submitted to Earth, Planets and Space (EPS

Chronometric Geodesy

International audienc

ACES Simulation User Manual

International audienc

Test of the gravitational redshift with satellites Galileo 5 and 6

International audienc