Complexity of future manned space flight mission control can be significantly reduced by integrating GPS, the PTTI source, into telemetry, tracking and command (TT&C). Future telecommunications, space tracking electronic intelligence, metrology, navigation, and data acquisition will thereby be sewed, including: (1) On-board ephemeris determination, (2) Reduced synchronization time for time division muUiple access (TDMA) links, and (3) In- flight clock calibration, increasing on-board autonomy and reducing ground support costs. Manned space transportation through the first quarter of the 21st century will probably depend on a mix of vehicles, including the Advanced Manned Launch System (AMLS), the Personnel Launch System (PLS), and continued use of the Shuttle Fleet. Precise Ephemeris is important on-board for mission success, status monitoring, also for rendezvous and docking. Use of GPS can eliminate ground based tracking/processing, enhancing autonomy and reducing communications bandwidth. GPS time can simplify complicated functions used in bandwidth efficient time division multiple access (TDMA) communications, such as: (1) Precise and real-time synchronization of receive reference timing, (2) nansmit-timing and acquisition control, (3) Unique synchronization word (UW) detection, and (4) Elastic buffering. High clock accuracy provides increased signal-to-noise (S/N) ratio during acquisition, permitting narrower acquisition frequency and time windows. Spaceborne systems requirements to provide capabilities such as: (1) Refinement of the GEM-72 gravity model based on satellite tracking observations from ATS-6 to GEOS-3, (2) Relativistic clock experiments, (3) NASA crustal dynamics program for developing space geodetic techniques to study the earth's crust, its gravity field, and earthquake mechanisms, and (4) Multi-disciplinary space geodetic tracking for studying global climatic changes are also reviewed.


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