GPS Applications to Launch Vehicles

This paper s ummarizes the findings of an on-going effort on GPS applications to the tracking of space launch ve- hicles. This effort is in response to the two areas of con- cern to Headquarters, Air Force Space Command (AFSPC): the cost-effectiveness of and the technical risk in adopting a GPS-based system for primary launch ve- hicle tracking and metric data processing. Since the cur- rent radar tracking systems at the Eastern and Western Ranges fall short of meeting the requirements of the fu- ture Spacelift Range System (SLRS) to be designed and developed by the Range Standardization and Automation (RSA) Program, the Air Force is exploring the feasibility and the cost-avoidance potential of a GPS-based range safety and instrumentation system. The application of GPS to launch vehicles presents diierent challenges from both satellite and earth-bound user navigation. A database on launch and ballistic vehicles’ recently compiled by The Aerospace Corporation provides information regarding the placement constraints on GPS antennas and user equipment. Also established in this effort is a boost phase environment profile envelope through which the on-board equipment must operate. These stringent constraints and severe environments are among the critical factors that challenge the success of a GPS-based range system. This paper explores the implications of these factors through the simulation of a Delta II launch. The results indicate that cooperative tracking between receiver channels is required to prevent data drop-out and to minimize undetected cycle slips in carrier phase measurement. GPS antenna configurations, signal/data management, and vehicle-ground station communication link are discussed vis-&-vis the launch vehicle specific conditions.