Author: Steven Platnick
Affiliation: NASA GSFC
Remote sensing algorithms are typically based on narrow-band observations using spectral regions chosen to maximize the information content for the geophysical quantity of interest. Solar reflected radiation (UV up to the midwave infrared) is useful for a variety of Earth remote sensing problems. We will briefly discuss passive remotes sensing strategies that use reflected solar radiances, and show example retrievals from satellite and airborne platforms. The emphasis will be on atmospheric quantities including cloud and aerosol optical and microphysical properties.
Remote techniques can be based on radiometric, polarization, or directional measurements, as well as various combinations. Of particular relevance is the use of radiometric measurements and their calibration traceability. Historically, radiometric quantities are radiance-based, requiring accurate knowledge of the spectral exo-atmospheric solar irradiance to convert to the fundamental reflectance quantity. Uncertainty in the spectral irradiance can be an important component to the overall reflectance uncertainty. Some current/future satellite sensors carry a reflectance-based standard onboard that is useful through the shortwave infrared. However, the midwave infrared portion of the spectrum (3.7 µm) remains problematic due to lack of a reflectance standard coupled with a scarcity of solar irradiance measurements. A summary of these issues will be presented.