First Global Retrievals of Solar Induced Chlorophyll Fluorescence from the SIFIS Instrument onboard the Chinese Goumang Satellite

In recent years, solar-induced chlorophyll fluorescence (SIF) has emerged as a powerful indicator for observing terrestrial photosynthesis. However, most existing satellite-based SIF retrievals are characterized by relatively coarse spatial resolutions, typically at the kilometer scale or coarser. The Chinese Terrestrial Ecosystem Carbon Inventory Satellite, Goumang, launched in August 2022, addresses this limitation by carrying the SIF Imaging Spectrometer (SIFIS), the first spaceborne instrument specifically developed for global SIF observations. SIFIS offers both high spatial resolution (370 m × 800 m) and high spectral resolution (0.24 nm across 664–786 nm), while achieving SIF retrieval uncertainties (~0.48 mW m⁻² nm⁻¹ sr⁻¹) comparable to those of existing satellite SIF products. The radiance measurements and SIF retrievals from SIFIS were initially evaluated using airborne AisaIBIS observations. Furthermore, SIFIS-derived SIF exhibits strong spatial and temporal consistency with independent satellite SIF datasets, as well as high correlations with flux tower estimates of gross primary production (R² = 0.87). Overall, this novel SIF product provides new opportunities to investigate photosynthetic processes at fine spatial scales from space.