In-flight performance of the Advanced Radiation Detector for UAV Operations (ARDUO)

Abstract

Natural Resources Canada is responsible for the provision of aerial radiometric surveys in the event of a radiological or nuclear emergency in Canada. Manned aerial surveys are an essential element of the planned consequence management operation, as demonstrated by the recovery work following the 2011 Tohoku earthquake and tsunami, and their effects in Fukushima, Japan. Flying lower and slower than manned aircraft, an unmanned aerial vehicle (UAV) can provide improved spatial resolution. In particular, hot spot activity can be underestimated in manned survey results as the higher flight altitude and wider line spacing effectively average the hot spot over a larger area. Moreover, a UAV can enter an area which is too hazardous for humans, due not only to the radiological threat which is its target, but also to other anticipated hazards such as explosives, airborne chemical hazards, or open water. Natural Resources Canada has been investigating the inclusion of UAV-borne radiation survey spectrometers into its aerial survey response procedures. The Advanced Radiation Detector for UAV Operations (ARDUO) was developed to exploit the flight and lift capabilities available in the under 25 kg class of UAVs. The detector features eight 2.8 cm × 2.8 cm × 5.6 cm CsI(Tl) crystals arranged in a self-shielding configuration, read out with silicon photomultipliers. The signal is digitized using miniaturized custom electronics. The ARDUO is flown on a main- and tail-rotor UAV called Responder which has a 6 kg lift capacity and up to 40 minute endurance. Experiments were conducted to characterize the performance of the ARDUO and Responder UAV system in both laboratory and outdoor trials. Outdoor trials consisted of aerial surveys over sealed point sources and over a distributed source of 10 MBq/m2 of La-140. Results show how the directional response of the ARDUO can provide an indication in real time of source location to guide the UAV during flight. As well, the results show how utilization of the directional information in post-acquisition processing can result in improved spatial resolution of radiation features for both point and distributed sources.