In the field of deep space exploration, an optical system was designed to meet the imaging detection requirements for shadowed regions on celestial surfaces. The system features a 45°×45° field of view, a 27.2 mm focal length, a spectral range of 430?680 nm, and a relative aperture of 1/2. To achieve high imaging quality and compact size, the design incorporates a novel symmetric optical structure based on the complexification of a positive lens near the aperture stop. The primary optical power of this structure integrates telephoto design elements, helping to reduce the system size. Through passive athermal optical design, the system can operate within a wide temperature range from -40 ℃ to +55 ℃. Additionally, precise micro-thermal stress design was applied to the double-cemented lenses to improve performance stability. During the design process, comprehensive analysis and optimization of the optical structure and aberrations resulted in excellent performance indicators: full-field distortion less than 3%, modulation transfer function value greater than 0.5 at a spatial frequency of 45.5 lp/mm within 0.9 normalized field of view, and total length of 72.8 mm. With its large field of view, large relative aperture, and compact size, the system enables rapid acquisition of target information during multiple takeoffs and landings in shadowed regions on celestial surfaces, while also reducing energy consumption and extending mission lifespan.