This section is intended to provide a background or context to the invention that is, inter alia, recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
Electromagnetic wave remote sensing of earth resources and weather has been studied in the past decades. For example, radar sensing is used in oil and mineral exploration, as well as in monitoring and predicting weather. In addition to these uses, remote detection of nuclear radiation is theoretically possible via electromagnetic wave sensing, because radiation-induced ionization in air increases radar reflectivity. Despite this ionization phenomenon and its associated applications, there has been little research on remote sensing of ionized air.
From a theoretical standpoint, the use of electromagnetic waves in detecting radioactive plumes from nuclear power plant operations has been investigated. Various works have reported radar cross section (RCS) of microwave scattering from charged dielectric spheres. From an experimental standpoint, an X-band Russian radar detected and tracked radioactive plumes from the 1986 Chernobyl accident. As a result of these experiments, the correlation between radioactivity and radar cross section was determined by calibrated measurements. Despite this work, the underlying physics has not been well established; as a result, the scientific community has viewed these results with little confidence. In spite of these initial experimental correlations, it has been found that existing simple plasma models under-predict the RCS by several orders of magnitude. In addition to the lack of understanding surrounding the correlation between radioactivity and radar cross section, current radiation detectors based on air sampling (e.g. ionization counters, scintillators, and semiconductors) are not effective from long distances because of dilution and atmospheric dispersion. Specifically, the limited range of conventional detectors is because of small penetration lengths of alpha and beta particles in air and a decrease of neutrons and gamma rays with the inverse of the square of the distance from the source. Consequently, such systems are limited to a detection range of approximately 100 meters. Thus, although the impact of radiation on electromagnetic waves in air has been generally understood, there is a need for a method and system for utilizing such a relationship without the need for close proximity to the radiation, i.e. a remote detection mechanism.