Wind study and GPS dropsonde applicability to airdrop testing

Abstract

Wind measurement accuracy has been demonstrated to be a significant factor in airdrop accuracy. The U.S. Army Yuma Proving Ground (YPG) has undertaken a study to better understand the behavior of winds both over a wide geographic area and over time. In addition, multiple systems for measuring and modeling winds have been evaluated. This paper addresses the following three areas: (1) documentation of the data collection and processing methods currently being used at YPG, (2) comparison of the performance of the wind estimation systems in use at YPG, and (3) assessment of the effectiveness of the Global Positioning System (GPS) Dropsonde techniques for wind estimation and post-processing of airdrop data in support of airdrop testing. Specifically, the paper assesses the ability of the GPS dropsonde techniques to sufficiently estimate true wind velocity for airdrop testing. The evaluation of the applicability of GPS-based dropsondes has involved addressing the following issues: (1) impact of the descent rate of the GPS dropsonde system on the wind estimate, (2) errors involved with using the GPS ground track velocities as the wind, estimate directly, (3) difference of accuracy of the two systems and the degree of accuracy required for this technique, and (4) the usefulness of the GPS dropsonde ground track datain post-processing when attempting to derive the actual trajectory of the payload.