Earth orientation parameters estimated from recent Australian mixed-mode and Southern Intensive sessions

Abstract

In principle, we can use geodetic Very Long Baseline Interferometry (VLBI) measurements to calculate all types of Earth orientation parameters (EOP), namely celestial pole offsets, polar motion, and UT1-UTC. However, the sensitivity toward the single EOP and the resulting accuracy strongly depends on the network extension, the session duration, and the recording rate. We can expect high-quality estimates from sessions with a well-distributed observation network designed for EOP determination, such as the R1 and R4 sessions. On the other hand, it takes quite a long time from the actual observation to the delivery of the analysis results. The 24-h sessions observed within the Australian mixed-mode program (AUA/AUM) do not provide a globally extended network of stations. Still, they involve the future potential to deliver results with a short latency. Under this aspect, we investigate the possibilities to determine different sets of or single EOP from the AUA and AUM sessions observed since 2020. The networks usually comprise the Australian stations (Ho, Hb, Ke, Yg) and the telescopes in South Africa (Ht) and New Zealand (Ww). Due to the spatial limitation of that constellation, the estimation of the complete set of EOP is not always favorable. Therefore, different analysis schemes are tested, including treating the 24-h sessions similarly to Intensive sessions. A subset of the telescopes (Hb, Yg, Ht) have been or are involved in observing the so-called Southern Intensive sessions since 2020. In addition to the results of the 24-h sessions, we present the UT1-UTC estimates derived from the latest Southern Intensives (2022, 2023).