Innovations in multi-spectral self-induced shock-layer radiance measurement, instrumentation, and data acquisition suite

Current and planned ground-based Ballistic Missile Defense (BMD) systems rely on optical seekers aboard interceptors that impact incoming warheads. For success, the interceptor system must acquire and track the target object, and then carry out maneuvers required for intercept. A main component of the target acquisition and tracking system suite is the optical sensor(s). Future missile interceptors are projected to fly at hypersonic velocities and will be expected to acquire and track the threat while traveling within the atmosphere. An interceptor traveling at hypersonic Mach numbers will experience aerodynamic heat loading that increases temperatures on external surfaces; including optical windows. Further, thermal excitation of species occurs in the flow-field around the interceptor. Emissions from hot optics and/or excited constituents in the sensor's field of regard can lead to sensor blinding in some regions of the spectrum. The Dual-mode Experiment on Bow* Technology Agent, AIAA member f Professor, Department of Physical Science, AIAA member * Technical Program Manager, Center for Space Engineering, AIAA member § Associate Professor, Department of Aerospace Engineering, AIAA senior member 1 Innovative Science and Technolgy Program Technology Agent, AIAA member * Associate Director, Engineering Sciences Division, AIAA Associate Fellow This paper is declared a work of the U.S. Government and is not subjected to copyright protection in the United States. 1 American Institute of Aeronautics and Astronautics (c)2001 American Institute of Aeronautics & Astronautics or Published with Permission of Author(s) and/or Author(s) Sponsoring Organization. shock Interactions (DEBT) project is designed to contribute further understanding toward the aerothermochemistry associated with hypersonic flight for interceptor applications within the Earth's atmosphere. Such detailed understanding is required to accurately model the optical radiation from high temperature flows. It is necessary to acquire dual-mode (ultraviolet and infrared) data during the mission flight to improve and/or validate state-of-art models developed under Ballistic Missile Defense Organization's (BMDO) Innovative Science and Technology Program. This paper summarizes the innovative solutions derived from lessons learned from the design and development of the DEBI instrumentation suite. Problems addressed were: (1) how to best detect and transport signals predicted in the short wave and mid wave infrared spectrum; (2) what detectors and wavelengths are best suited to optics constraints; (3) what new materials were necessary to improve signal to noise for a sensible acquisition system; and (4) how to design an optical payload that can perform as required in a harsh environment. Ultimately, the intention of this work is to provide BMD engineers and scientists the predictive capability necessary to design sensor systems that will be effective under flight conditions. Introduction Current and planned ground-based BMD systems Figure 1. Illustration of in-flight hypervelocity induced bow-shock on nose of the DEBI experimental vehicle. rely on optical seekers with a hit-to-kill (HTK) strategy or blast fragmentation warhead to impact the incoming warhead. For this, the kinetic kill vehicle (KKV) must sense and track the target candidate and carry out the maneuvers required for the HTK intercept. For endo-atmospheric interceptors flying at hypersonic velocities the aerodynamic heating loads will significantly increase temperatures on external surfaces, including optical windows. Further, thermal excitation of species occurs in the flow field around the KKV. Given that the seekers operate in the infrared spectrum, emissions from hot optics