High-frequency Earth rotation parameters estimated from VLBI observations during CONT campaigns

The Desai–Sibois high-frequency Earth rotation parameter (HF-ERP) model provides one of the most detailed descriptions of diurnal and sub-diurnal variability up to date. However, it still underrepresents short-period signals, underscoring the need for reliable, observation-based HF-ERP series for ERP model validation and excitation studies. In this study, we analyzed data from the continuous very long baseline interferometry (VLBI) campaigns (CONT08–CONT17) to estimate ERP with daily and hourly resolution. The weighted root mean square (WRMS) of the daily-derived polar motion (PM) and the length of day (LOD) range from 24 to 47 μas and 4 to 8 μs, respectively, with CONT14 achieving the best accuracy (PM ≈ 25 μas; LOD ≈ 4 μs) owing to its denser and more balanced network geometry, while hourly solutions are approximately an order of magnitude less accurate than daily estimates (PM: 130–255 μas; UT1: 10–16 μs). Fast Fourier transform (FFT) analysis of the hourly series reveals pronounced peaks at the dominant diurnal and sub-diurnal harmonics, with residual power in the 6–12 h band and sidebands near 12 h and 24 h after subtraction of the HF-ERP model. Our results demonstrate that the daily solutions from CONT14 can meet the Global Geodetic Observing System (GGOS) 1-mm (~ 30 μas) accuracy target with two-week latency. We also demonstrate VLBI’s capability for HF-ERP estimation and indicate that the existing HF-ERP models require further refinement to more accurately represent short-period excitations beyond the modeled tidal terms. Graphical Abstract