VLBI Relativistic Time Delay Model with Picosecond Precision

Abstract

The VLBI relativistic time delay model of transformation is reformuled with a precision of better than 1 ps, which is given as follows

where is geocentric newtonial potential, and are the barycentric velocity vector in B-frame and the geocentric velocity vector of antenna i. Ŝ is the unit vector of the direction from the barycenter of solar system to the source. c is the speed of light in vacuum. , where is the geocentric baseline vector. δt_v can be expressed as in which and

where Δt_atm , Δt_ion and Δt_axo are the tropospheric, the ionospheric and the axio offset refraction delays respectively, and Δt_grav is called the gravitational time delay. A straightforward differentation of expression (1), the equation of d(dτ)/dt can be obtained. The included in the can be expressed as

The orders of magnitude of the various correction terms in expression (4) and (5) are estimated respectively. Conclusion: expression (4) and (5) should be taken into account in the VLBI relativistic model of transformation for the 1 ps precision. Equation (1) and the expression of its differentation differ from all the models which have been published earlier.