A first look at mixed VGOS-S/X correlation and post-processing

25th European VLBI Group for Geodesy and Astronomy Working Meeting, 14-18 March 2021The processing of geodetic VLBI experiments involving both S/X and VGOS stations is highly desirable for a multitude of reasons. Beyond the express purpose of obtaining geodetic ties between existing S/X stations and the rapidly expanding network of VGOS stations, a period of overlap and integration between the two systems is beneficial in order to help preserve reference frame continuity during the transition from the S/X to VGOS network, as well as to provide an opportunity to study any systematic differences between the two. Therefore, it is important to correlate and fringe-fit data collected contemporaneously by both S/X and VGOS stations to obtain delay observables on mixed baselines. A brief overview of one possible implementation of this process will be presented, describing correlation (including the use of the DiFX zoom-bands feature) along with the peculiarities of data handling on mixed S/X-VGOS baselines during post-processing with fourfit. Some results from the mixed-mode sessions RD2005 and RD2006 will be presented, and future prospects will be discusse