Design of a low-cost, lightweight, passively cooled, narrowband, SWIR camera for space-based imaging

This document describes the conceptual design for a spaceborne imager operating in the short-wave infrared (SWIR). The instrument was designed to image a single emission line of OH from the night sky from a satellite in low Earth orbit, but much of the design is relevant to other imaging applications. The imager has a 23.40 FOV in the crosstrack direction with a resolution of 1.6 mrad. It functions like a line scanner but incorporates a two-dimensional (256 x 256) InGaAs focal-plane array (FPA) to attain high signal-to-noise. It employs a set of telecentric foreoptics to accommodate narrowband imaging, but a simpler design would serve for broadband measurements. It uses a small radiator to passively cool the FPA to < 200K and direct radiation by the support assembly to reduce the temperature of the optics. A novel approach that accomplishes TDI (time, delay, integrate) off of the focal plane obviates the need for a step/stare mirror. The design has no moving parts, weighs less than 6 kg, and consumes less than 15 W of power.