Light propagation in the gravitational field of N arbitrarily moving bodies in the 1.5PN approximation for high-precision astrometry

摘要

High-precision astrometry on sub-micro-arcsecond level in angular resolutionrequires accurate determination of the trajectory of a light-signal from thecelestial light source through the gravitational field of the Solar systemtoward the observer. In this investigation the light trajectory in thegravitational field of N moving bodies is determined in the 1.5 post-Newtonianapproximation. In the approach presented two specific issues of particularimportance are accounted for: (1) According to the recommendations of International Astronomical Union, themetric of the Solar system is expressed in terms of intrinsic mass-multipolesand intrinsic spin-multipoles of the massive bodies, allowing for arbitraryshape, inner structure and rotational motion of the massive bodies of the Solarsystem. (2) The Solar system bodies move along arbitrary worldlines which can laterbe specified by Solar system ephemeris. The presented analytical solution for light trajectory is a primaryrequirement for extremely high-precision astrometry on sub-micro-arcsecondlevel of accuracy and associated massive computations in astrometric datareduction. An estimation of the numerical magnitude for time delay and lightdeflection of the leading multipoles is given.