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Mock Observations for the CSST Mission: Main Surveys--the Stray Light

Xian Jing-Tian, Lin Lin, Fang Yue-Dong, Zhang Xin, Xu You-Hua, Meng Xian-Min, Tian Hao, Zhang Tian-Yi, Ban Zhang, Li Guo-Liang, Xu Shu-Yan, Wang Wei

Abstract

Stray light significantly influences the detection capabilities of astronomical telescopes. The actual stray-light level during observations depends not only on the telescope's inherent stray-light suppression capability but also on its operational orbit conditions. Accurate estimation of stray-light levels is crucial for assessing image quality and performing realistic scientific simulations. To rapidly estimate stray-light levels under realistic, complex operational conditions, we developed an analytical model tailored to the China Space Station Telescope (CSST). Our model simulates stray-light backgrounds generated by off-field sources such as moonlight, starlight, and earthshine, incorporating the effects of zodiacal light, as well as scattering and ghost images induced by bright in-field stars. The proposed method allows quick and accurate evaluation of stray-light conditions, facilitating both image simulation and observational scheduling.

Mock Observations for the CSST Mission: Main Surveys--the Stray Light

Abstract

Stray light significantly influences the detection capabilities of astronomical telescopes. The actual stray-light level during observations depends not only on the telescope's inherent stray-light suppression capability but also on its operational orbit conditions. Accurate estimation of stray-light levels is crucial for assessing image quality and performing realistic scientific simulations. To rapidly estimate stray-light levels under realistic, complex operational conditions, we developed an analytical model tailored to the China Space Station Telescope (CSST). Our model simulates stray-light backgrounds generated by off-field sources such as moonlight, starlight, and earthshine, incorporating the effects of zodiacal light, as well as scattering and ghost images induced by bright in-field stars. The proposed method allows quick and accurate evaluation of stray-light conditions, facilitating both image simulation and observational scheduling.

Paper Structure

This paper contains 15 sections, 17 equations, 12 figures, 1 table.

Table of Contents

  1. Introduction
  2. STRAY LIGHT SOURCES AND THEIR PROPAGATION MECHANISMS
  3. Primary Sources
  4. Out-of-field Stray Light Propagation Mechanisms
  5. In-field Stray Light Propagation Mechanisms
  6. Calculation methods for stray light from out-of-field sources
  7. Calculation method for out-of-field point sources
  8. Calculation Method for Earthshine
  9. Comparision of Earthshine between CSST and HST
  10. Calculation methods for stray light from in-field sources
  11. Calculation Method for Zodiacal Light
  12. Scattering by Bright Stars on the Surfaces of Main Optical Components
  13. Ghost Images Between the Filter and Detector
  14. Image simulation with in-field stray light
  15. Conclusion

Figures (12)

  • Figure 1: CSST and its aperture door Zhan2021
  • Figure 2: The main sources and propagations of stray light
  • Figure 3: Scattering caused by CSST’s main system optical components (Primary mirror, Secondary mirror, tertiary mirror and fast steering mirror) We assume a single-direction parallel rays entering the system, which under ideal conditions would form a point image on the focal plane. However, due to scattering from the mirrors, stray light is distributed everywhere of the focal plane.
  • Figure 4: Reflections between filter and detector
  • Figure 5: The calculation process of stray light from out-of-field sources
  • ...and 7 more figures