THE USE OF GPS TRACKING AND GUIDANCE SYSTEMS FOR THE CHICKEN LITTLE JOINT PROJECT’S “ACOUSTIC WEEK” FLIGHT TEST PROGRAM

A two-week flight test effort was conducted in September 2003 at a remote location at Eglin Air Force Base in Florida. Dubbed “Acoustic Week”, the test was sponsored by the Chicken Little Program Office and the National Ground Intelligence Center. The test was designed to examine the effectiveness of data collection techniques for a variety of sensors, while simultaneously collecting signature data for a variety of aircraft. Eight aircraft were tested including two rotorcraft from the United States Army Lead The Fleet program, a Navy fixed wing unmanned air vehicle (UAV), a prototype rotary wing UAV, and four civil helicopters. Sensors included acoustic and seismic arrays, infra-red measurement devices, and a human sound jury. Essential vehicle position data were acquired by five different organizations using five different systems of varying accuracy and quality. The focus of this paper is the GPS tracking system used by an Army/NASA/Boeing test team to provide flight path guidance cues, as well as to acquire precise vehicle position data, for two of the test vehicles. The measurement technique used to obtain vehicle source noise hemispheres and the use of these noise hemispheres to predict ground noise footprints is discussed and the need for precise vehicle position data and precision flight tracks is investigated. A detailed description of GPS tracking systems, sources of analysis errors and data accuracy degradation, and the criticality of instrumentation installation on system performance are provided. Flight track results document the improvement in deviations from the desired flight track when guidance cues are provided by course and glide slope deviation indicators rather than the typical ground reference cues.