Mitigating Source Structure in Geodetic VLBI on the Visibility Level

TL;DR

This paper addresses the challenge of source structure effects in geodetic VLBI by developing tools to mitigate their impact on visibility data, aiming to improve the accuracy of station coordinates and reference frame stability.

Contribution

The paper introduces a novel method to remove source structure effects directly from visibility data in VGOS observations, enhancing geodetic measurement precision.

Findings

Tools successfully mitigate source structure effects

Improved accuracy in station coordinate estimation

Enhanced stability of the celestial reference frame

Abstract

Geodetic and astrometric VLBI has entered a new era with the implementation of the VLBI Global Observing System (VGOS). These broadband and dual linear polarization observations aim at an accuracy of station coordinates of 1 mm and a reference frame stability of 0.1 mm/year. Although the extended brightness distribution of many of the radio-loud active galactic nuclei observed during geodetic VLBI sessions is resolved by the interferometer, the established processing chain still treats these objects as point sources. We investigate the impact of source structure on the visibility level and develop tools to remove the structure from the visibility data, right after correlation. Here we present our approach and show results obtained from observational VGOS data.