Spectral Fidelity of Earth's Terrestrial and Aquatic Ecosystems

The Surface Biology and Geology (SBG) investigation aspires to create global maps of spectral surface reflectance and emissivity at a cadence of 16 days or better. For the first time these spectroscopic maps will have coverage to address global system-level questions about Earth's geology, cryosphere and ecosystems. The revolutionary potential poses a commensurate challenge: creating contiguous maps free from regional biases induced by atmosphere, geometry, or inversion error. To this end, high spectroscopic precision with uniform spectral response and stable spectral calibration will be crucial. This study quantifies the impact of spectral fidelity on SBG's aquatic and terrestrial ecosystem objectives. We find that contemporary algorithms for ecosystem trait retrieval demand better fidelity and uniformity than that of historical missions. Spectroscopic nonuniformities that have previously been considered acceptable can cause systematic errors larger than the instrument noise and of the same order as the variability SBG aims to measure. Moreover, their impact on atmospheric correction can induce climate-dependent systematic errors that thwart comparisons between ecosystems. These results underscore the importance of spectral uniformity in SBG sensor design.