Mock Observations for the CSST Mission: Multi-Channel Imager--Instrument Simulation

TL;DR

This work presents a comprehensive instrument-simulation framework for CSST-MCI, detailing the optical architecture, PSF modeling, and end-to-end image synthesis across UV–NIR channels. It integrates wavefront aberration budgets, non-ideal detector effects, and realistic sky backgrounds to generate level-0 to level-1 data products, enabling robust calibration and pipeline development. The study demonstrates the framework’s utility via star/galaxy image simulations, Bayesian flux calibration using Gaia XP data, and advanced multi-exposure coaddition with the UPDC algorithm, which improves detectability and preserves morphological details. Acknowledging parameter uncertainties, the authors advocate a three-phase refinement strategy—laboratory measurements, pre-launch calibration, and post-launch analyses—to continuously improve the simulation fidelity and mission planning.

Abstract

The Chinese Space Station Survey Telescope (CSST), a two-meter aperture astronomical space telescope under China's manned space program, is equipped with multiple back-end scientific instruments. As an astronomical precision measurement module of the CSST, the Multi-Channel Imager (MCI) can cover a wide wavelength range from ultraviolet to near-infrared with three-color simultaneous high-precision photometry and imaging, which meets the scientific requirements for various fields. The diverse scientific objectives of MCI require not only a robust airborne platform, advanced optical systems, and observing facilities but also comprehensive software support for scientific operations and research. To this end, it is essential to develop realistic observational simulation software to thoroughly evaluate the MCI data stream and provide calibration tools for future scientific investigations. The MCI instrument simulation software will serve as a foundation for the development of the MCI data processing pipeline and will facilitate improvements in both hardware and software, as well as in the observational operation strategy, in alignment with the mission's scientific goals. In conclusion, we present a comprehensive overview of the MCI instrument simulation and some corresponding performances of the MCI data processing pipeline.

Figures (21)

• Figure 1: Schematic diagram of the optical path of the optical system of the CSST.
• Figure 2: Schematic diagram of the optical system of the MCI.
• Figure 3: Schematic diagram of the simulation process of the MCI instrument
• Figure 4: The simulated wavefront aberration distribution of the MCI at 633nm.
• Figure 5: The simulated PSF data at the wavelength of 633nm.