First, the existing communications architecture of each NAVSTAR segment was examined. If it appeared not feasible to change a segment's communications architecture, redesign of the segment's communications architecture was not further considered. Similarly, the segment's hardware and software architecutre was also considered; if it was infeasible to change the segment's hardware and software architecture, hardware/software redesign of this segment was not further considered. Redesign was considered for those segment components whose communications and/or hardware/software architectures could be feasibly altered.