File Acta Futura Acta. Futura. Relativistic Positioning Systems
Acta Futura 7 (2013) 79-85 Acta DOI: 10.2420/AF07.2013.79 Futura Relativistic Positioning Systems and Gravitational Perturbations A G,* Faculty of Mathematics and Physics, University of Ljubljana, Jadranska ulica 19, 1000 Ljubljana, Slovenia Centre of Excellence SPACE-SI, Aškerčeva cesta 12, 1000 Ljubljana, Slovenia U K, M H, Faculty of Mathematics and Physics, University of Ljubljana, Jadranska ulica 19, 1000 Ljubljana, Slovenia S C, ESA - Advanced Concepts Team, ESTEC, Keplerlaan 1, Postbus 299, 2200 AG Noordwijk, Netherlands P D LNE-SYRTE, Observatoire de Paris, CNRS and UPMC ; 61 avenue de l’Observatoire, 75014 Paris, France Abstract. In order to deliver a high accuracy and time via the time difference between the emission relativistic positioning system, several gravitational and the reception of the signal. However, due to the in- perturbations need to be taken into account. We ertial reference frames and curvature of the space-time therefore consider a system of satellites, such as in the vicinity of Earth, space and time cannot be con- the Galileo system, in a space-time described by a sidered as absolute. In fact, general relativistic effects are background Schwarzschild metric and small grav- far from being negligible [2]. Current GNSS deal with itational perturbations due to the Earth’s rotation, this problem by adding general relativistic corrections multipoles and tides, and the gravity of the Moon, the Sun, and planets. We present the status of this to the level of the accuracy desired. An alternative, and work currently carried out in the ESA Slovenian more consistent, approach is to abandon the concept of PECS project Relativistic Global Navigation Sys- absolute space and time and describe a GNSS directly in tem, give the explicit expressions for the perturbed general relativity, i.e.
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