Plots of closure amplitudes at the X band for source 0059+581 as a function of GMST for two quadrangles, (a) NYALES20–TSUKUB32–WETTZELL–WESTFORD and (b) KATH12M–KOKEE–NYALES20–WETTZELL. See Figure 5 for a description of the plot design. The structure effects shown in the two plots reveal that 0059+581 was temporarily extended, for instance, in 2007, 2013, and 2015.