Source structure effects in VLBI Global Observing System (VGOS) observations

VLBI Global Observing System (VGOS) is now regularly observing to produce the best geodetic VLBI data ever, with a thermal noise level of about 3 ps. However, the systematic errors due to angular structure of the radio sources are becoming prominent in these high-precision VGOS observations. It is important to understand, study, and monitor these systematic errors with the aim to model them in geodetic data processing. Improvements have been made to derive structure images and Gaussian components at the four bands (3 – 14 GHz) directly from VGOS observations. One of the biggest challenges has now been identified to be aligning the images over both time and frequency to create a consistent model for a given source. We will also report the near-future work plan about modeling the effects of source structure.