中文摘要：

在毫米波被动探测中，天空亮温直接影响到金属目标的探测与识别。建立了晴天、云、雨等天气下的天空亮温计算模型，并在3mm波段计算了天空亮温。在几种典型天气条件（晴天、多云、阴天、降雨）下对天空亮温进行了实验测量。计算和测量结果表明，云层对天空亮温的影响要视云中液态水密度、云的厚度、离地面的高度而定，降雨对天空亮温影响随降雨率增大而增大。

英文摘要：

Sky brightness temperature directly affects the metal target detection and identification in the passive millimeter wave detection. Theoretical models for brightness temperature have been developed, and sky brightness temperatures are calculated at 3 mm band. Experimental measurements are carried out at several different weather conditions （such as clear, cloudy, overcast, rainy）. Calculation and measure- ment show that impact of cloud on sky brightness temperature depends on liquid water density, cloud thickness and height from the ground and the affect of rain on sky brightness temperature increases with rain rate.