Imaging VGOS Observations and Investigating Source Structure Effects

The next-generation, broadband geodetic very long baseline interferometry system, named VGOS, is being developed globally with an aim to achieve 1 mm accuracy for station positions. Currently, the systematic errors in VGOS delays are still about 20 ps. In this study, we demonstrate that it feasible make images directly from observations without need of complicated calibrations and determine source structure effects through process model fitting phases our imaging results. Source investigated detail, shown well explained by these effects. For instance, root-mean-square (RMS) closure sources 0016 + 731 1030 415 24.9 50.2 ps session VO0034, respectively; after correcting based on images, RMS values residual 5.5 10.1 jumps delay observables magnitudes several hundreds picoseconds found be caused 2? phase shifts among four bands due strong impact alignment at frequency discussed. Our study provides a methodology deriving radio discusses bands, which fundamental mitigating