DOI: 10.25966/gadk-6y76
NASA Goddard Space Flight Center geodetic Very Long Baseline Interferometry (VLBI) quarterly solutions for UT1 provide estimates of UT1 angle that characterizes the Earth rotation using least squares in analysis of group delays derived from analysis of 496,659 group delays determined from processing 1-hr single baseline geodetic VLBI experiments accumulated since since 1990.01.03 through 2025.06.03 on a quarterly basis. The data used in these solutions are available from the NASA Crustal Dynamics Data Information System (CDDIS).
Single baseline experiments are sensitive to only two out of three Earth orientation parameters. In these solution only UT1 angle that characterizes variation in accumulated position angle of the Earth in the equatorial plane is determined. Estimated parameters are UT1, clock function, atmospheric path delay in zenith direction. Other parameters, such as station positions, source coordinates, and high frequency harmonic variations in the Earth rotation are not estimated, but kept fixed to the vales determined from the global gsf solution.
The quarterly NASA solutions for UT1 from 1-hr VLBI experiments:
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