Airborne Measurements of Earth Surface Temperature (Ocean and Land) in the 10-12-micro and 8-14-micro Regions.
Field experience using infrared radiometers for making airborne measurements of land and ocean surface temperature show that an atmospheric induced error and a surface reflectivity error are present when the 8-14-micro atmospheric window is used. It is generally accepted that the error can be minimized by working in a narrow region of the atmospheric window centered about 10.5 micro. In order to evaluate the improvement in performance using the narrow band filter region, simultaneous airborne measurements were made with two Barnes model PRT-5 infrared radiometers flown side by side over land and water areas for a range of altitudes up to 8000 ft (2440 m). One radiometer contained an 8-14-micro (standard) filter, and the second contained a 10-12-micro filter. Comparison of the data shows the narrow band filter to reduce the measured error 1.5-2.0 times compared with the wide band filter. The data also show that the error increases approximately linearly with altitude, and therefore by taking measurement at two altitudes and linearly extrapolating to ground level, an accuracy of measurement of a few tenths of a degree Celsius is possible.