Generating chemical plumes for imaging spectrometers: Equipment and procedures

The Aerospace Corporation's portable chemical release equipment has been used for some time to discharge gases and atomized liquids into the atmosphere at accurately measured flow rates, thereby producing chemical plumes whose column densities can be determined by remote infrared imaging spectrometers. Column densities can be converted into mass flow rates with a knowledge of the wind speed, the air temperature, and the ground and/or the sky radiometric temperature, which are also measured at the chemical release site, simultaneously with the release. Chemical releases have been, and continue to be, used to determine the smallest chemical plume that can be detected by an imaging spectrometer under varying conditions and to determine the accuracy to which it can infer chemical flow rates, air temperature, and wind speed. This paper describes the equipment and procedures used to release chemicals into the atmosphere and make the required meteorological and radiometric temperature measurements. The accuracy of each measurement is given.