Relativistic Theories

New methods enabling to carry out the calculation of the light bending due to gravity without having to determine the light rays are designed for modeling astrometry missions like GAIA with an accuracy better than the microarcsecond. These methods can also be applied to the relativistic modeling and data analysis of the micro-wave time link of the ACES space project. The requirements the orbitography has to fulfill in order to be consistent with the relativistic corrections at the expected level of accuracy are analyzed.

The concept of relativistic positioning systems as location systems using the electromagnetic signals generated by four emitters (pulsars, satellites...) is proposed and developed. Such a system enabling to locate spatial or terrestrial radio stations by using millisecond pulsars signals is under examination. Relativistic positioning systems offer also a new, fully relativistic way of understanding and operating global navigation satellite systems (GNSS) like GPS or Galileo.

Left: Deflection of a light ray by Jupiter. (C) Christophe Le Poncin-Lafitte, Grégoire Gitton, SYRTE- Observatoire de Paris.
Right: Galactic positioning system for the solar system.

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