On the possibility of sensing an early stage fire in moving vehicles by microwave radiometry

This paper deals with passive remote sensing of fire spots in moving vehicles by a ground-based microwave radiometer mounted near a rail or a road. Images have been simulated at 30 GHz, identifying also dielectric properties of the vehicle wall able to guarantee a penetration of the microwave radiation. The 30-GHz operative frequency can be considered a trade-off between the antenna system dimensions and the penetration capability of microwave radiation through a dielectric wall. It has been seen that the radiation associated to the fire spot emerges distinctly through a dielectric wall in several cases, depending also on fire dimensions, loss tangent values of the wall, and its thickness. This study confirms that the detection of an early stage fire through a dielectric wall by microwave radiometry is promising, taking into account that the use of infrared sensor systems mainly depends on emissivity knowledge of the vehicle surface and on the heating of the monitored external wall