Temporal Behavior of Natural Terrain Radiance at Infrared Wavelengths

摘要

Because most infrared observation of natural terrain are made at infrequent orwidely spaced time intervals, there is little information on the high time resolution variation in background radiance. This is in spite of the fact that meteorological and other influences can cause apparent radiance to change by amounts equivalent to a few degrees Kelvin in seconds or tens of seconds. Infrared imagery acquired during the recent Smart Weapons Operability Enhancement Joint Test and Evaluation allows the investigation of the nature of IR radiance fluctuations with high time resolution under a variety of dirunal and meteorological conditions. During the Grayling I deployment, images were acquired at a rate of 6.25 frames per second, for 10 s every five min during each of the 2 h mission periods. There were 107 mission periods during the 41-day test. A portion of these images have been segmented according to homogeneous features (determined independently of the image content) and histograms of apparent temperature within those features have been processed to allow studies of the temporal variation of radiance. The nature of the fluctuations as a function of meteorological, atmospheric, and diurnal conditions is discussed; however, the result of this study is that the range of variation within the 10 s period, for the missions studied, is very small. The largest range observed for any of the ROIs was 1 K.