February 19, 2016 The first fringes recently obtained with the 12-meter antenna marked the dawn of the VGOS broadband era. But there is also an important linkage to the existing “legacy S/X” VLBI network that is right next door and connected around the world. Indeed, the 20-meter antenna at KPGO, which is currently configured to observe with the legacy S-band and X-band receivers that are operational at VLBI geodetic sites worldwide, can also form baselines with the new broadband systems under a “mixed-mode” configuration that makes the broadband and the legacy S/X networks compatible. On February 12, the KPGO operational team run a mixed-mode fringe test with the KPGO 12-meter and 20-meter antennas configured in broadband and legacy S/X modes, respectively. The mixed mode produced the first fringes thus establishing a short baseline that ties over 20 years of operation with the legacy VLBI network to the broadband VGOS network of the future. An intra-KPGO short-baseline tie can be realized by configuring (left) the 20-meter antenna as a legacy S/X VLBI system and (right) the 12-meter antenna as a broadband VGOS system using common observing frequencies and a mixed-mode correlation method.
