Implications of Atmospheric Temperature Fluctuations on Passive Remote Sensing of Chemicals

Passive remote sensing of airborne chemicals at infrared wavelengths may be limited by temporal fluctuations in atmospheric brightness temperatures delta T(Delta t). The fluctuations delta T increase the minimum detectable chemical vapor concentration-pathlength product (CL) given by the noise-equivalent-CL (NECL) of the measurements scenario. Brightness temperatures in two infrared spectral bands were measured on clear and cloudy days along three lines of sights. For time windows Delta t 3-5 s, delta T(Delta t) remained constant at the sensor noise-level and rapidly increased as Delta t increased. The fluctuation time scale for the cloudy day was longer than those for the clear day and the magnitude of the fluctuations was smaller. At the conditions of clear day tests, passive remote sensing of airborne chemicals would have reached its maximum sensitivity with an integration interval Delta t = 3-5 s with sensitivity diminishing fast with longer detection time-windows. See also ADM002075. Presented at the Army Science Conference (25th) held in Orlando, FL on 27-30 November 2006. The original document contains color images.