Joint Retrieval of CO₂ and CH₄ Concentrations for the Multi‑Spectral Imaging Carbon Observatory (MUSICO)

A joint retrieval algorithm for CO₂ and CH₄ concentrations is presented for the Multi‑spectral Imaging Carbon Observatory (MUSICO). This instrument is based on a Fabry‑Pérot (FP) imaging spectrometer to be deployed on the Chinese Space Station in 2026, and is designed to quantify facility‑scale emissions at 100 m spatial resolution. MUSICO acquires high‑resolution spectra in the CO₂ (1595–1620 nm) and CH₄ (1630–1655 nm) bands.

A central challenge for point-source imaging is systematic bias from atmospheric aerosol scattering, which perturbs top-of-atmosphere radiance and degrades gas retrievals. We address this within an optimal-estimation framework that integrates aerosol correction by combining multi-angle observations, enabled by steerable pointing, with auxiliary channels (O₂ near 765 nm and aerosol-sensitive bands at 440, 685, and 865 nm). This synergy improves the separation of aerosol-induced radiance perturbations from true gas absorption.

The forward model is based on MODTRAN and includes spectrally resolved gas absorption, surface reflectance, and multiple scattering. End-to-end simulations show that the integrated methodology effectively mitigates aerosol-induced biases and enables the mission to meet its accuracy targets for monitoring anthropogenic point sources.