FINCH EYE: The Optical and Optomechanical Design of a GRISM-based SWIR Hyperspectral Imaging Payload for a 3U CubeSat

Crop residue is an important metric used for agricultural land-use monitoring and climate science research. Estimating crop residue coverage is essential to sustainable agricultural practices. The University of Toronto Aerospace Team is developing FINCH EYE, the optical payload for the upcoming FINCH 3U CubeSat, to measure crop residue cover. We conceived of a novel ultra-compact push-broom architecture with a volume phase-holographic grism dispersive element to keep the design compact and simplify the mechanical assembly. The FINCH EYE will image hyperspectral data from 900nm to 1700nm at 10nm spectral resolution, with a spatial resolution of 100m, and a SNR of 100. In this paper, we will describe the optical design of FINCH EYE, which consists of a commercial objective lens, an InGaAs camera, and a custom lens-grism-lens spectrograph. We will also describe the optomechanical housing, emphasizing design features that facilitate proper alignment during assembly.