A freeform optical design of a 12U CubeSat for Earth observation

Large-scale, multi-redundant satellite platforms are well known for their high cost and the extensive time required for their construction and deployment. In recent decades, small satellites like CubeSats have gained significant popularity and transformed the field of space exploration. This article presents a preliminary optical design for a CubeSat dedicated to Earth observation in the 400-900 nm spectral range. The CubeSat is based on a 12U platform, with the optical part occupying 8U and featuring a two-mirror off-axis Schwarzschild configuration. The satellite will perform hyperspectral imaging of the Earth using the pushbroom acquisition technique, all within a compact and efficient system. To achieve this, a linear variable filter will be placed in front of the detector. Due to their small size, CubeSats present some limitations compared to larger, traditional satellites, which degrade the optical performance of the imaging systems. To overcome these limitations, an optical design based on freeform optics has been developed. A preliminary analysis of a two-mirror system, both with and without freeform optics, will be presented to demonstrate how the integration of freeform surfaces can substantially improve the system optical performance.