Stray light suppression design for the ET Transit Telescope

To ensure that The Earth 2.0 (ET) transit telescopes achieves the ultra-high-precision photometric capability required for detecting exoplanets, the internal stray light background noise must be suppressed to an extremely low level. This paper aims to complete an efficient stray light suppression design through systematic simulation analysis and verification. Using TracePro optical analysis software, an accurate model of the transit telescope was constructed, incorporating all optical and mechanical components and surface properties (such as the Bidirectional Scattering Distribution Function (BSDF) of black paint coatings). Stray light simulation analysis was conducted using the forward ray-tracing method to identify critical stray light paths. Furthermore, the Point Source Transmittance (PST) values at different off-axis angles of the light source were calculated. The results indicate that the combined effect of multi-stage baffles and highly absorptive coatings significantly suppress