The in-band detection and characterization of a laser beam is a difficult problem because its directionality severely limits the ability to place an intercept sensor in the mainbeam and the amount of sidelobe energy available for intercept. However, the potential exists to detect and characterize a laser beam by exploiting changes it induces in the atmosphere. As a high-power laser propagates through the atmosphere, it changes the index of refraction of the air and this change will disturb the propagation of radio frequency (and microwave) signals. The laser-induced discontinuity in the index of refraction serves as a radar target. The meteorological community has used radar for many years to detect and characterize changes in the index of refraction on the same order as the changes induced by a high-power laser beam. The purpose of the proposed work is to investigate and characterize the atmospheric changes induced by a high-power laser and the radio frequency scattering from those induced changes, which will support a study on the feasibility of detecting and characterizing high-power laser beams using radar. This research establishes a solid foundation for the development of a unique method based on radar to provide an out-of-band, off-axis laser detection and characterization capability. Because the radar method does not rely on in-band sidelobe or scattered energy, it should not need precision cueing (time and location) information and thus, has the potential for a search capability. The results of this research project will provide an enduring capability for the community by characterizing and modeling the atmospheric changes induced by the high-power laser and the electromagnetic scattering from those changes. These results form the basis for developing the capability to sense high-power laser through indirect means. The results of the radar feasibility study will provide foundation for assessing and guiding the development of high-power laser sensing methods and systems.
