The primary NASA need for this technology is to measure spectrally resolved light absorption by atmospheric aerosols for its Airborne Measurement program. At present, aerosol light absorption is measured by collecting sample on a filter subtract and measuring light extinction and scattering of the collected samples during the airborne measurements. This method suffers from a number of intrinsic errors. The proposed RGB DPAS technique will be far more sensitive than the filter-based techniques, and is capable of providing 1s data acquisition measurement. Additionally, past NASA programs such as EXCAVATE, APEX, UNA-UNA, and AAFEX have had as a major focus, on the measurement of black carbon emissions from civilian aircraft engines. Since mass absorption coefficient of black carbon is known at several visible wavelengths, the proposed DPAS aerosol absorption monitor can be used as a black carbon emission monitor.
We expect that the 3-color RGB DPAS aerosol absorption monitor developed under this program will significantly benefit the atmospheric science community in characterizing the radiative properties of ambient aerosols. The ability of the proposed instrument to simultaneously measure particle absorption with good time resolution and high precision in three colors will enable continuous measurements of the particle optical absorption that can be directly used by regional and global climate forcing models. In combination with the Cavity Attenuated Phase-Shift (CAPS) extinction monitor, which represents a dramatic improvement on current particle extinction measurement technology, single particle albedo of ambient aerosols could be directly determined. Since aerosol scattering of solar radiation causes atmospheric cooling, whereas absorption can cause atmospheric warming, direct measurements on single particle albedo of ambient aerosols are critical in understanding aerosol effect on the Earth radiative balance.