GPS Ground Control Upgrade Set for September Jul 31, 2007 GPS World The U.S. Air Force said Monday that the planned upgrade of the GPS command and control system, first announced early this year, is slated to occur the second week of September. Dubbed the Architecture Evolution Plan (AEP), the upgrade will replace the Air Force's entire GPS master control station, including both software and hardware, some of which dates back to GPS's inception in the 1970s. The upgrade will, among other things, prepare the master control station to work with the latest generation of Block IIF satellites when they go into orbit, according to the Air Force.The AEP transition will take place over a period of four to six days; it will phase in a few satellites in the GPS constellation at a time, and will be completely reversible if it encounters any problems, the Air Force said. Before it begins, both old and new ground control systems will be synchronized in terms of positioning data, namely their reception of satellites' timing and navigation signals, down to the millimeter level—users of the system should not notice the transition, according to the Air Force.However, should they experience any problems or anomalies during the transition period, they should follow the normal notification procedures through the U.S. Coast Guard Navigation Center.The AEP will retain all of the legacy monitoring stations around the world currently utilized by the U.S. Air Force, as well as the National Geospatial-Intelligence Agency (NGA) monitoring stations around the globe originally added as part of the Legacy - Accuracy Improvement Initiative. Additional NGA monitoring station sites are in the process of being brought on-line for future inclusion within the AEP, however.