Multi-Aperture Hypersonic Imager

ABSTRACT: The Air Force is requires an innovative multi-aperture sensor for mid-wave infrared (MWIR) and long-wave infrared (LWIR) capable of extended operation at a speed between Mach 4 and Mach 7 and an altitude between 50,000 and 70,000ft, for navigation and terminal homing applications. The leading edge of a vehicle traveling at Mach 7 may experience temperatures over 1700C, while typical optical materials such as Zinc Sulfide (ZnS) oxidize at around 200C. OPTRA proposes a system based on a multi-aperture telescope. This approach uses multiple small optical windows, minimizing atmospheric distortion across each window and enabling conductive cooling of the windows through their mounting surfaces. For sufficiently small light sources, this approach can match the resolution achievable with a single large aperture and enables the use of an algorithm to remove atmospheric distortion. The sensor will have an outer layer made from a heat-resistant alloy, and an inner layer made from a material with high thermal conductivity which will be actively cooled. The heat load on the optical windows will be dissipated by thermal conduction through the inner layer. A prototype will be designed based on results from fluid, thermal and optical simulations using FEA, as well as from breadboard tests. BENEFIT: Resolution of 1.5 arc-minutes at 10m for sufficiently small light sources Small individual windows enable conductive cooling of infrared windows in hypersonic airstream Small individual windows minimize atmospheric distortions across each window Algorithm using closure phases eliminates phase errors between windows for sufficiently small sources Physically conformal: sensor surface contours can exactly match the desired vehicle surface contours