• Application of GPS to Hybrid Integrated Ranges and Simulations

      Van Wechel, R. J.; Jarrell, R. P.; Interstate Electronics Corp. (International Foundation for Telemetering, 1995-11)
      GPS user equipment has matured and is now available to support the use of live players in integrated ranges and simulations. P-code GPS provides true WGS-84 based coordinate information anywhere in the world at any time and to accuracies at the 5 ft (1s) level (demonstrated in high dynamic aircraft using differential P-code GPS). C/A code GPS shows lower accuracy and is especially vulnerable to multipath degradation over water. In supporting networked ranges with simulations, GPS is directly applicable to the dead reckoning requirements of the Distributed Interactive Simulation (DIS) community. DIS dead reckoning provides the capability of much reduced data rates in recovering TSPI information from platforms. The on-board state vector for an integrated GPS/Inertial Reference Unit provides accurate position, velocity and acceleration as well as attitude and attitude rate information so that dead reckoning thresholds can be both position and attitude driven. A simplified analysis is presented in the paper to derive dead reckoning update rates from the G loading levels of various player dynamics. Also, information is provided which results in word length requirements for GPS-based state vector information for transmission over minimum word length DIS Field Instrumentation Protocol Data Units (PDUs, which are the data block formats). The coordinate frame problem in use of GPS-based state vector information from fixed ranges is also addressed, showing that the use of a local geodetic frame is preferable to the use of an earth centered earth fixed frame, in that it is more efficient of network PDU word length.
    • A GPS-Based Autonomous Onboard Destruct System

      Alves, Daniel F., Jr.; Keith, Edward L.; Alpha Instrumentation and Information Management; Microcosm Inc. (International Foundation for Telemetering, 1995-11)
      This paper examines the issues involved in replacing the current Range safety infrastructure with an autonomous range safety system based on GPS (Global Positioning Satellite) integrated navigation system solutions. Range safety is required in the first place because current launch vehicle navigation systems cannot meet a level of trust needed to determine if the mission is really under control and on course. Existing launch vehicle navigation is generally based on attitude and acceleration sensing instrumentation that are subject to drift, initialization errors and failures. Thus, a launch vehicle can easily be under the control of a seemingly operating navigation system, yet be steering the launch vehicle along an incorrect and dangerous flight path. Inertial-based navigation systems are good, but they cannot be trusted. The function of Range safety is to assure that untrustworthy navigation is backed up with a trusted system that has positive knowledge of the launch vehicle location, and the intelligence to decide when and where a launch vehicle must be destroyed. Combining inertial navigation, GPS derived position information and knowledge-based computer control has the potential to provide trusted and autonomous Range safety functions. The issues of autonomous Range safety are addressed in this paper.