星载毫米波亚毫米波辐射计定标的初步研究

Study on the Calibration of the Millimeter and Submillimeter Wave Radiometer

星载微波辐射计采用平方律检波,物体的辐射功率与接收机的输出电压成线性关系。因此星载微波辐射计采用高低温两点定标。其中高温定标源采用处在环境温度下的黑体,低温定标源为冷空背景辐射。由Rayleigh-Jeans公式计算的物体的辐射功率与其物理温度成线性关系,但是随着物体频率的升高,Rayleigh-Jeans公式与Planck定律的近似误差越来越大,此时应根据Planck定律计算物体的辐射功率。从Planck定律出发,对毫米波、亚毫米波辐射计的定标方程进行了推导,并给出了高低温定标源的辐射功率在毫米波和亚毫米波段的表达式。

Microwave spaceborne radiometer adopts sqare-law detection, so the radiation of the object received is linear to the output voltage of the radiometer. Therefore,the calibration of microwave spaceborne radiometer is performed by measuring the radiometer response to hot and cold references during operation. The hot reference is usually a blackbody under environmental temperature,and the cold reference is Cosmic Background Radiation. According to Rayleigh-Jeans law, the emission of the object is directly linear to its absolute temperature. As the frequency of object increases, Rayleigh-Jeans Law deviates from Planck＇s Blackbody Radiation Law,and the radiation of object received should be calculated according to Planck＇s Blackbody Radiation Law. The calibration equations of millimeter and submillimeter radiometer are derived from the Planck＇s Law,and the formulas of the calibration references radiation are presented in millimeter and submillimeter bands.