Obtaining local-tie vectors from short-baseline interferometry between legacy S/X and VGOS telescopes at Ny-Ålesund

With the ongoing transition for geodetic Very Long Baseline Interferometry (VLBI) from the use of legacy S/X telescopes to the VLBI Global Observing System (VGOS), it is necessary to connect the new VGOS network to the existing legacy S/X telescopes. One way to do this is through specially designed short-baseline interferometry sessions with the aim to obtain local-tie vectors between these telescope generations at observatories that host both legacy S/X and new generation VGOS telescopes. The dismantling of the legacy S/X telescope NYALES20 at the Ny-Ålesund Geodetic Earth Observatory in August 2023 was preceded by around one and a half years of short-baseline interferometric measurements, referred to as NYTIE, to the new VGOS telescopes NYALE13S and NYALE13N. The results of these measurements are used to connect the old and new networks at this observatory. We present both group and phase delay results of this dedicated measurement campaign. We also analyze the same baselines with data that can be obtained from regular IVS-R1 and IVS-R4 sessions. We find a significant discrepancy between group and phase delay positions in the vertical component. Sensitivity tests attribute this discrepancy to session-dependent differential troposphere effects rather than to telescope deformation modeling. Both group and phase delay results are consistent with a classical geodetic survey using total station and GNSS once the formal uncertainties are rescaled to reflect the observed session-to-session scatter and a residual modeling systematic of 7 mm is taken into account.