AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
A New Concept for Aerosol Satellite Remote Sensing in the Twilight Zone
HANS MOOSMULLER, Michealene Iaukea-Lum, Jeffrey LaCombe, Eric Wang, Desert Research Institute
Abstract Number: 529 Working Group: Instrumentation and Methods
Abstract Satellite remote sensing of atmospheric aerosols is important for understanding the effects of aerosols on radiative forcing and climate change, visibility, and air quality. Most satellite instruments used for this purpose are flown on polar, sun-synchronous orbits with typical mid-day overpass times. Examples include NASA’s Terra and Aqua satellites with overpass times of 10:30 in a descending node for Terra and 13:30 in an ascending node for Aqua. Aerosol characterization over the ocean takes advantage of a fairly dark background lightened by aerosol scattering. Measurements over land surfaces are much more difficult, especially for high and variable surface albedos including snow and ice and desert surfaces. These difficulties are due to the inherent brightness of the surface that makes detection of aerosol scattering challenging.
Here, we propose a satellite flying in a polar, sun-synchronous, dawn-dusk orbit enabling observation of the twilight zone where the earth surface is several orders of magnitude darker than during mid-day, because it doesn’t receive any direct solar illumination. On the other hand, aerosols in the atmosphere may still be illuminated, depending on their altitude, distance from the dawn-dusk line, and surface topography. The illumination-observation geometry is fairly unique with a ~90° scattering angle between the near horizontal solar illumination and the nadir-looking observation. This will result in unique polarization observations as p-polarized light will not be observed for spherical scatterers and will indicate depolarization by non-spherical scatterers.
We propose to utilize this concept for the sensitive satellite characterization of atmospheric aerosols with a multi-spectral camera imaging the twilight zone. Initial development will include stratospheric balloon-borne imaging during sunset and sunrise in conjunction with vertical in-situ aerosol characterization during ascent and co-located AERONET observations, analysis of data from geostationary satellite imagers, and working toward development of a dawn-dusk orbiting CubeSat.