Design of a large-aperture telescope with four visible-infrared channels sharing a common front off-axis afocal optic...

To meet the requirements for large-area coverage, multi-band, and high-precision Earth observation, integrating a large-aperture front end with a multi-band back end has become the mainstream approach. However, conventional systems are often limited by on-axis obstruction, aberrations induced by beam splitting, and challenges in design and alignment. This paper presents a modular design based on a shared off-axis afocal telescope that serves four spectral channels: visible, SWIR, MWIR, and LWIR. The three infrared channels are designed as reimaging systems with real exit pupils, achieving a cold-shield efficiency greater than 97.5% and incorporating athermalization across the temperature range of -20 °C to +40 °C. The integrated system has an aperture of 2000 mm and a field of view of 1.2°×1.2°, which eliminates on-axis obstruction and simplifies system integration. At an orbital altitude of 36,000 km, the system provides continuous full-time coverage over a 700 km × 700 km area, with ground resolutions of 12 m, 60 m, 85 m, and 200 m in the respective bands. Both the individual optical modules and the fully integrated system achieve diffraction-limited imaging performance. Each module can be independently aligned, assembled, and tested, providing a practical reference for the engineering implementation of a large-aperture, multi-band remote sensing systems.