The impact of celestial pole offset modelling on VLBI UT1 Intensive results

TL;DR

This paper evaluates how celestial pole offset models influence VLBI UT1 estimates, demonstrating that neglecting or differing models can introduce systematic errors up to 20 microarcseconds, affecting the accuracy of Earth rotation measurements.

Contribution

The study systematically compares three CPO models and quantifies their impact on UT1 estimates, highlighting the importance of accurate celestial pole modeling in VLBI data processing.

Findings

Neglecting CPO modeling causes up to 20 microarcseconds systematic errors.

Different CPO models lead to UT1 estimate differences of about 10 microarcseconds.

Results are applicable to satellite data processing as well.

Abstract

Very Long Baseline Interferometry (VLBI) Intensive sessions are scheduled to provide operational Universal Time (UT1) determinations with low latency. UT1 estimates obtained from these observations heavily depend on the model of the celestial pole motion used during data processing. However, even the most accurate precession-nutation model, IAU 2000/2006, is not accurate enough to realize the full potential of VLBI observations. To achieve the highest possible accuracy in UT1 estimates, a celestial pole offset (CPO), which is the difference between the actual and modelled precession-nutation angles, should be applied. Three CPO models are currently available for users. In this paper, these models have been tested and the differences between UT1 estimates obtained with those models are investigated. It has been shown that neglecting CPO modelling during VLBI UT1 Intensive processing causes systematic errors in UT1 series of up to 20 microarcseconds. It has been also found that using different CPO models causes the differences in UT1 estimates reaching 10 microarcseconds. Obtained results are applicable to the satellite data processing as well.