Mock Observations for the CSST Mission: CPI-C -- Targets for High Contrast Imaging

TL;DR

The paper presents CPISM, a Python-based, modular simulator for CPI-C on the CSST that bridges target modeling, optical imaging, detector response, and data-product generation to enable end-to-end planning and pipeline validation. By integrating Fourier-optics-based PSF propagation, a deformable-mirror–assisted dark hole, realistic cosmic-ray and background modeling, and EMCCD detector physics, CPISM generates Level 0 data and enables SNR, contrast, and photometric analyses. Key contributions include a flexible target/spectrum modeling framework (CK04 and planetary reflection spectra), a detailed five-module architecture, and validation demonstrations (PSF chromaticity, a hypothetical exoplanet around Alpha Centauri, and photometric consistency with input spectra). The framework supports extensibility through replacement of spectral libraries, atmosphere simulators, and instrument models, thereby aiding CPI-C observation planning, risk mitigation, and scientific planning for exoplanet discovery and characterization. Overall, CPISM stands as a practical tool to optimize high-contrast imaging campaigns, quantify detection prospects, and improve the scientific return of the CPI-C mission.

Abstract

We introduce CPISM, a simulation program developed for the Cool Planet Imaging Coronagraph (CPI-C) on the China Space Station Telescope (CSST). CPISM supports high-contrast exoplanet imaging by simulating observational conditions and instrumental effects to optimize target selection and observation strategies. The modular design includes target modeling, imaging simulation, observational effects, detector response, and data product generation modules, enabling flexible and realistic synthetic observations. Validation through simulations of a bright star shows strong agreement with theoretical expectations, confirming the program's accuracy. CPISM's modular design allows flexibility, accommodating different stellar and planetary models, and can simulate instrumental noise, cosmic rays, and other observational effects. This tool aids in data processing, signal-to-noise ratio analysis, and high-contrast photometry, contributing to future exoplanet discovery and characterization efforts. The program's outputs will enhance observation planning and scientific return for the CPI-C mission, providing critical insights into exoplanetary systems.

Figures (11)

• Figure 1: The working flowchart of the CPISM program.
• Figure 2: An image of CPI-C level 0 data simulated by the CPISM program. The frame contains 1080 × 1050 pixels. With the adopted pixel scale of 0.016153 $\mathrm{arcsec\, pix^{-1}}$, this corresponds to an on-sky footprint of 17.45 $\mathrm{arcsec}$ × 16.96 $\mathrm{arcsec}$. The color bar indicates the pixel value (analogue-to-digital units, ADU) on a linear scale.
• Figure 3: Schematic diagram of CPI-C Level 0 data storage folder structure.
• Figure 4: The stellar spectra of different spectral types (F5V, G5V, K5V) and their corresponding blackbody spectra across varying V-band magnitudes are generated by the program.
• Figure 5: The the geometric albedo spectra of planets with difference atmosphere parameters. Top: Spectra of different metallicity parameters when the sedimentation efficiency parameter is constant. Right: Spectra of different sedimentation efficiency parameters when the metallicity parameter is constant.