Translate between reflectance in unitless quantities and inverse steradians.
Spectroscopic remote sensing records the intensity of light in hundreds of different wavelengths to measure the physical and chemical composition of the Earth’s surface. By measuring hundreds of distinct channels simultaneously, spectrometers can uniquely identify the spectral fingerprints of diverse physical processes within a pixel. This can enable more quantitative and accurate physics-based measurements than conventional multiband remote sensing. Spectra are initially measured in radiance units, representing light intensity at the sensor as a function of wavelength. Atmospheric radiative transfer modeling is then used to infer the surface reflectance spectrum, which holds information about the physical and chemical properties of the target pixel. Reflectance spectra provide a wealth of remote sensing information for studies of such diverse topics as vegetation, aquatic ecosystems, the cryosphere, and geology.