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The Advanced Infrared Detection Assembly Dual Band (AIDA-2B) project, part of the Skyward instrument, is an imager that consists of a main Aluminum alloy metallic frame attached to the Sensor Head Unit (SHU) chassis by means of thirteen screws. The imager features several subassemblies among which the FOV change & focusing mechanism. This mechanism has two separately actioned trolleys that allow the FOV change and focusing movement. Each trolley moves on two linear ball slides and is actuated by a lead screw. In order to achieve challenging optical performance target in the infrared range, the introduction of chalcogenide glass is required. IG4 is the material selected for the lens installed on one of the two trolleys of the focusing mechanism. Such material features excellent thermal properties (such as almost constant refraction index in the whole temperature range), but suffers from an extreme fragility and very weak mechanical properties. In order to employ such material in a challenging mechanical environment such as an airborne IRST instrument a 'floating' design is necessary, with the glass attached to the mechanical mounting by means of adhesive pads, and no metal-glass contact. A description of the design solutions developed, manufactured and qualified for the most critical optical mount inside the Instrument is presented. This paper contains a collection of mechanical results obtained on the optical mount breadboards, including a description of environmental tests performed. Three configurations for the lens mounting have been designed and tested: 1. C-shaped profile; 2. Thin ring; 3. Crown ring. The comparison between these high stability optical mounts based on adhesive joints, as well as the acceptance criteria derived in order to establish the flight worthiness of the manufactured and assembled hardware, are presented in this paper.
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