Advanced electro-optical analysis and adhesion angle optimization of curved secondary mirror holders in small satellites

This study introduces a novel electro-optical (EO) performance analysis of secondary mirror holders in small satellites, pioneering the concept of adhesion angle (α[jls-end-space/]) as a key parameter in optical system optimization. While curved holders have been recognized for their advantages in minimizing diffraction effects, the specific role of adhesion angle in image quality metrics Point Spread Function (PSF), Modulation Transfer Function (MTF), Radiometric Characteristics (Signal to Noise Ratio (SNR)), and Spatial Resolution (Ground Sampling Distance (GSD), Ground Resolved Distance (GRD), and Swath) has not been previously explored. A Cassegrain type optical telescope with a 190 mm primary mirror diameter and an effective focal length of 1000 mm was designed to address small satellite constraints, such as limited payload volume, mass, and launch conditions. The study employs MTF degradation modeling, PSF energy distribution analysis, and Fourier-based frequency evaluation to assess the impact of adhesion angles. Results indicate that the optimized Model C (α = 60°) curved secondary mirror holder demonstrated superior optical performance, achieving the system cross-track MTF of 16.1% and the system along-track MTF of 10.9%, with minimal diffraction artifacts. Detailed MTF analyses showed MTF_opt at 25.9%, MTF_sensor at 63.7%, MTF_imager at 16.9%, MTF_jitter at 95.2%, MTF_smear at 99.6%, MTF_gvm at 100.0%, and MTF_flm at 67.8%. Compared to a straight, 3-arm holder with an optical MTF of 24.90%, the adhesion angle optimization improved MTF performance by 4.016%. Radiometric analysis revealed enhanced imaging sensitivity, with SNR values of 77.1, 58.3, and 45.2 after applying 4 × 4 pixel binning. Spatial resolution analysis confirmed that native GSD increased from 0.5 m at 250 km to 1.3 m at 650 km, while GRD varied from 0.9 m to 2.3 m at 550 nm, demonstrating a strong dependence of resolution on orbital altitude. Experimental star test validation confirmed consistency between simulation and real-world performance, with Model C effectively minimizing diffraction spikes. This study is the first to introduce adhesion angle optimization as a key factor in enhancing imaging efficiency and diffraction suppression for compact optical payloads. To validate the general applicability of adhesion angle optimization, the method was applied to a Ritchey–Chretien optical payload with a primary mirror diameter of 150 mm, increasing the MTF_opt from 29.89% to 30.85%, demonstrating a 3.21% improvement. The findings establish adhesion angle selection as a crucial determinant of high-resolution imaging capabilities, contributing to the next-generation design of small satellite optical systems.