The empirical Earth rotation model from VLBI observations

Abstract

Aims. An alternative to the traditional method for modeling the kinematics of the Earth's rotation is proposed. The purpose of developing the new approach is to provide a self-consistent and simple description of the Earth's rotation in a way that can be estimated directly from observations without using intermediate quantities.Methods. Instead of estimating the time series of pole coordinates, the UT1-TAI angles, their rates, and the daily offsets of nutation, the method for estimating coefficients of the expansion of a small perturbational rotation vector into basis functions is proposed. The resulting transformation from the terrestrial coordinate system to the celestial coordinate system is formulated as the product of the a priori matrix of a finite rotation and an empirical vector of a residual perturbational rotation. In the framework of this approach, the specific choice of the a priori matrix is irrelevant, provided the angles of the residual rotation are small enough to neglect their squares. The coefficients of the expansion into the B-spline and Fourier bases, together with estimates of other nuisance parameters, are evaluated directly from observations of time delay or time range in a single least square solution.Results. This approach was successfully implemented in a computer program for processing VLBI observations. The dataset from 1984 through 2006 was analyzed. The new procedure adequately represents the Earth's rotation, including slowly varying changes in UT1-TAI and polar motion, the forced nutations, the free core nutation, and the high frequency variations of polar motion and UT1.

Deep extragalactic VLBI-optical survey (DEVOS)

“…These are known VLBI sources (Beasley et al 2002;Helmboldt et al 2007) and have a relatively large number (13 and 16) of matching FIRST/SDSS quasars in their neighbourhood, according to the selection criteria above. The equatorial coordinates of the calibrators are determined in the International Celestial Reference Frame (ICRF) with mas or sub-mas accuracy (Petrov 2007), allowing us to determine the high-accuracy ICRF positions of the target sources through relative VLBI astrometry. There is a small overlap (3 common sources) between the two fields (Field A around J1616+3621 and Field B around J1623+3909).…”

The LBA Calibrator Survey of southern compact extragalactic radio sources - LCS1

“…The displacements due to loading caused by variations in soil moisture and snow cover in accordance with the GLDAS Noah model (Rodell et al 2004) with a resolution 0.25 × 0.25 deg 2 were computed using the same technique as the atmospheric pressure loading. The empirical model of harmonic variations in the Earth orientation parameters heo_20101111 derived from VLBI observations according to the method proposed by Petrov (2007) was used. The time‐series of UT1 and polar motion derived by the NASA Goddard Space Flight Center operational VLBI solutions were used a priori.…”

The theory of canonical perturbations applied to attitude dynamics and to the Earth rotation. Osculating and nonosculating Andoyer variables

“…This way of osculation loss might be a flaw of the Kinoshita-Souchay theory, had we expected it to render the angular velocity with respect to a precessing frame. In reality, the osculation loss is an advantage of the theory, because the presently available experimental technique (Schreiber et al 2004, Petrov 2007) provides for the measurement of the angular velocity relative to the inertial frame -the velocity furnished by the Kinoshita-Souchay theory.…”