Coordinated Aerobiological Sampling of a Plant Pathogen in the Lower Atmosphere Using Two Autonomous Unmanned Aerial Vehicles

Unmanned aerial vehicles (UAVs) are an important tool to track the long-distance movement of plant pathogens above crop fields. Here, we describe the use of a control strategy (coordination via speed modulation) to synchronize two autonomous UAVs during aerobiological sampling of the potato late blight pathogen, Phytophthora infestans. The UAVs shared position coordinates via a wireless mesh network and modulated their speeds so that they were properly phased within their sampling orbits. Three coordinated control experiments were performed August 14-15,2008. In the first two experiments, two UAVs were vertically aligned at two different altitudes [25 and 45 m above ground level (AGL)] with identical sampling orbits (radii of 150 m). In the third experiment, two UAVs shared the same altitude (35 m AGL) with different sampling orbits (radii of 130 and 160 m). Orbit times did not vary significantly between the two UAVs across all three aerobiological sampling missions, and the phase error during sampling converged to zero within 2 mm following the start of the coordinated control algorithm. Viable sporangia of P. infestans were recovered following two of the coordinated flights. This is the first detailed report of autonomous UAV coordination during the aerobiological sampling of a plant pathogen in the lower atmosphere. UAVs operating independently of one another may experience significant sampling variations during the course of a flight. Coordinating the flight of two or more UAVs ensures that the vehicles enter, sample, and exit a spore plume at consistent times. (C) 2010 Wiley Periodicals, Inc.