A study from the Changchun Institute of Optics, Fine Mechanics and Physics, University of Chinese Academy of Sciences, reports a comprehensive analytical model tailored for the Chinese Space Station Survey Telescope, achieving rapid and accurate estimation of stray light levels under realistic orbital conditions.

Stray light acts as a persistent interference for astronomical observations. Unwanted radiation originating from various sources, including the Sun, the Moon, and Earth, significantly degrades image quality by increasing background noise, reducing contrast, and obscuring faint celestial targets. For space missions equipped with a wide field of view and operating in a dynamic low Earth orbit, managing this interference is particularly challenging but critical for optimizing observational efficiency and ensuring data integrity. Traditional analysis methods, such as ray tracing, provide detailed visual tracking of light propagation but struggle to handle the heavy computational load required to simulate the rapidly changing illumination environment of a full survey mission simultaneously.

To address these computational limitations, the research team develops a novel and efficient strategy that conceptually separates the inherent stray light suppression capability of the telescope from the dynamic external illumination conditions. The researchers employ a point source transmission function to quantitatively characterize how the internal baffles, blocking rings, and optical components suppress off axis light at various incident angles. Recognizing the structural complexity of the observatory, the team constructs a robust and highly reliable transmission lookup matrix through a hybrid approach. This approach combines detailed computer ray tracing simulations with rigorous laboratory measurements taken directly from the actual telescope structure using a large collimated light source. Such an innovative method allows for the swift calculation of stray light intensity from a multitude of external sources, including sunlight, moonlight, and planetary light, by seamlessly integrating the real time orbital position data with the established suppression characteristics.

The comprehensive study also incorporates a detailed analysis of in field stray light sources, such as the zodiacal light scattered by interplanetary dust particles and the disruptive scattering and ghost images caused by bright stars located within the observational field of view. By carefully modeling the microscopic surface irregularities of the primary and secondary optical mirrors, as well as the complex multiple reflections bouncing between the spectral filters and the detector surfaces, the analytical system accurately predicts how these bright optical artifacts disperse across the focal plane. Furthermore, the research highlights the significant and complex influence of earthshine, which consists of solar and lunar light reflecting off the varied surface of Earth and scattering into the aperture. The comparative analysis demonstrates that the telescope requires exceptionally large avoidance angles from the bright limb of Earth to maintain sufficiently low background noise levels, a crucial finding that directly informs and refines the operational avoidance strategies of the entire mission.

In conclusion, this advanced analytical framework provides a powerful and indispensable tool for the upcoming space survey mission. By enabling realistic scientific image simulation and facilitating smart observational scheduling, the model ensures that the telescope can navigate the severely light polluted environment of low Earth orbit effectively and safely. Ultimately, this precise quantification of stray light interference clears the path for the space observatory to maximize its scientific output, protect its sensitive instruments, and deliver pristine, high quality astronomical data that will deepen our fundamental understanding of the universe.