Run the robot backward

This paper reports on lessons learned in sensor placement and search strategies for nuclear forensics from a 2013 field exercise. Nuclear forensics, where a radiological source is located, has been the subject of theoretical research but only one reported instance with an actual robot (Fukushima). The field exercise specifically focused on source localization where a teleoperated Packbot 510 UGV Radiac AN/UDR-14 dosimeter was used to find a 1.48 GigaBecquerel cesium-137 source placed in a partially collapsed building. The operators were able to quickly find the correct room but not the source, spending 30 minutes searching a 6 by 6 m space due to inconsistent measurements. A detailed analysis of the logged data shows that the readings were more reliable and suitable for an autonomous search algorithm when the robot was driven backwards. This counter-intuitive result appears due to unfavorable sensor placement. However, given that all robots have limited areas that sensors can be mounted on and have metal parts, it may be unrealistic to focus on optimizing radiological sensor placement on non-holonomic platforms. Instead, this paper recommends research in autonomous localization strategies that will compensate for inevitable imperfect readings.