Boost Phase Plume-to-Hardbody Handover

Several plume-hardbody handover algorithms under development by various investigators show promise in simulations for locating the missile body when the body is resolved or approximately the size of a pixel. Several scenarios involving liquid propellant missiles, such as the cases where these threats are observed at moderate to long ranges, and are at near nose-on geometries or large angles of attack, provide challenges to these handover algorithm and corresponding single- or dual-wavelength infrared detector concepts, however. These stressing conditions are challenging to space and air based systems that are employed to provide accurate metrics for reconstruction of threat trajectories or to provide position information for mid-course intercept, especially considering the preferred use in these systems of wavebands optimized for plume detection. In the enhancement plume flight regime (typically 70-200 km altitude for ICBM class missiles), plume radiance patterns exhibit a characteristic parabolic shape. This parabola is maintained even at large angles of attack. In some cases, the windward side may be significantly brighter than the leeward side and may present a "bright spot" that competes with the localized "vacuum core" signature, which is often used as an aim-point for the handover algorithms. Therefore, fitting the radiance pattern to this characteristic parabola provides a means for determining the plume axis, which then allows for more robust aim-point estimation. Relatively straightforward interpretation of the radiance patterns, possibly augmented with off-board information or information gained from multiple frames of data, allows for the determination of whether the threat is observed at near nose-on aspect angles or high angles of attack and the subsequent selection of the correct "bright point " that includes the missile body. Additionally, the parabola contains information that may be exploited to reveal characteristics of the propulsion system for identification of the upper stage missile system.