Validation of Autonomous Airborne Refueling Algorithms Using Flight Test Data

Successful Autonomous Airborne Refueling (AAR) has the potential to increase the mission range of unmanned aerial vehicles (UAVs). AAR requires that the position of the receiving aircraft relative to the tanker be known very accurately and in real time. In addition, to ensure safety and operational usefulness, the navigation architecture must provide high levels of integrity, continuity, and availability. We begin this paper with a reminder of the latest proposed Shipboard Relative GPS (SRGPS) navigation architecture, which we exploit as a preliminary basis for AAR navigation. The AAR mission is different from SRGPS because of the potentially severe sky blockage introduced by the tanker, which degrades the positioning accuracy. In this work, we provide a high accuracy and high fidelity dynamic blockage model for a KC-135 tanker. AAR flight tests were conducted to obtain time-tagged GPS and INS data that were processed offline in order to validate the KC-135 blockage model and the AAR navigation algorithms. Finally, a worldwide global AAR availability analysis is presented for a grid of 10 degrees in latitude and longitude.