• PHASE CENTER PROBLEMS WITH WRAP-AROUND ANTENNAS

      Meyer, Steven J.; Kujiraoka, Scott R.; Naval Air Warfare Center Weapons Division (International Foundation for Telemetering, 2002-10)
      The Joint Advanced Missile Instrumentation (JAMI) program is integrating Global Positioning System (GPS) technology into missile telemetry systems. The weakest link appears to be the GPS antenna. The antenna on a missile is required to be flush mounted for aerodynamic reasons. Due to the missile’s tendency to roll, the antenna needs to be a multi-element omnidirectional antenna array. Therefore an antenna used on missiles is a wrap-around antenna since it will meet the flush mount and rolling requirements by giving omnidirectional coverage. JAMI has used readily available techniques for designing wrap-around telemetry antennas to develop a GPS wrap-around antenna and has discovered a major problem. The Phase Center of a wrap-around antenna tends to be a surface, not a point, and not necessarily at the centerline of the missile body. GPS measurements have been conducted to determine the Phase Center of the antenna. When the Phase Center is large, the GPS receiver perceives it as multipath and integer ambiguities cannot be resolved. This paper addresses the problems that have been uncovered and outlines the steps that are planned to resolve them.
    • A STATUS REPORT OF THE JOINT ADVANCED MISSILE INSTRUMENTATION PROJECT HIGH DYNAMIC GPS- WE FINALLY GOT IT

      Powell, Dave; Scofield, Don; Naval Air Warfare Center Weapons Division (International Foundation for Telemetering, 2002-10)
      Joint Advanced Missile Instrumentation (JAMI), a Central Test and Evaluation Investment Program (CTEIP) initiative, is developing advanced telemetry system components that can be used in an integrated instrumentation package for tri-service small missile test and training applications. JAMI demonstrated significant improvement in the performance of low-cost Global Positioning System (GPS) based Time-Space-Position Information (TSPI) tracking hardware that can be used for world-wide test and training. Acquisition times of less than 3 seconds from a cold start and tracking dynamics to over 60 Gs were demonstrated. The design of a programmable Flight Termination Safe and Arm device has been completed. This paper discusses the progress of the program during the past year and the efforts planned for fiscal year 2002. High dynamic testing results of GPS and Inertial measurement Unit (IMU) devices and problems encountered are discussed.
    • TIME, SPACE, POSITION INFORMATION UNIT MESSAGE STRUCTURE OVERVIEW

      Meyer, Steven J.; Naval Air Warfare Center Weapons Division (International Foundation for Telemetering, 2002-10)
      The Joint Advanced Missile Instrumentation (JAMI) program is developing a Time, Space, and Position Information (TSPI) unit for high dynamic missile platforms by employing the use of Global Position System (GPS) and inertial sensors. The GPS data is uncoupled from the inertial data. The output of the JAMI TSPI unit follows the packet telemetry protocol and is called the TSPI unit message structure (TUMS). The packet format allows the data stream to stand on its own, be integrated into a packet telemetry system or be an asynchronous data channel in a PCM data stream. On the ground, the JAMI data processor (JDP) Kalman filters the GPS and inertial data to provide a real time TSPI solution to the ranges for display. This paper gives an overview of the message format, the timing relationships between the GPS data and inertial data, and how TUMS is to be handled by the telemetry receiving site to hand it off to the JDP.