Unclassified Gps Instrumentation in Ballistic Missile Intercept Test and Evaluation

GPS instrumentation capable of measuring a missile intercept event with less than 2-centimeter accuracy has been demonstrated in a special high speed/acceleration sled test at Holloman AFB. Although the basic instrumentation technique is well defined, plans to properly exploit this capability are yet to be adequately addressed. This paper reviews the demonstrated differential GPS instrumentation technique that achieves 2-centimeter accuracy and then discusses the factors that need be addressed to properly exploit this capability. It describes the important and unique attributes of high-precision GPS measurements in regard to missile intercept evaluation. The difference between accurate GPS end-game trajectory measurements and a direct impact-point measurement are contrasted to emphasize the benefits of the GPS methodology. The basis for the preferred translatorbased versus receiver-based GPS instrumentation is discussed with particular attention to the risk benefit of the translator approach. The challenges of GPS instrumentation on the interceptor are discussed with suggested implementation alternatives related to antenna design, digital versus analog translator design, dual versus single frequency use, and GPS signal bandwidth. Finally, an instrument configuration is described that can achieve the desired measurement accuracy with minimum risk.