SCHED can leave stations out of a scan if they get there much later than most stations in order to help increase the number of scans in a geodetic sequence. If the source being checked is important for the slow station, it can be blocked from being selected at this pass so that it can be selected later when the slow station can get there in a more timely manner. The effect of doing this tends to be that the slow antennas get used in roughly every other scan (the slew calculation knows if an antenna has the full time of the previous scan to get where it is going). In the current algorithm, if the station arrives more than GEOSLOW seconds after the third to last antenna to get there, it can be left out. Average and median times have been tried as the reference, but there tend to be issues when not all antennas were in the previous scan.