A Multipoint Correction Method for Environmental Temperature Changes in Airborne Double-Antenna Microwave Radiometers

Jian Sun,Kai Zhao,Tao Jiang

doi:10.3390/s140507820

Abstract

This manuscript describes a new type Ka-band airborne double-antenna microwave radiometer (ADAMR) designed for detecting atmospheric supercooled water content (SCWC). The source of the measurement error is investigated by analyzing the model of the system gain factor and the principle of the auto-gain compensative technique utilized in the radiometer. Then, a multipoint temperature correction method based on the two-point calibration method for this radiometer is proposed. The multipoint temperature correction method can eliminate the effect of changes in environmental temperature by establishing the relationship between the measurement error and the physical temperatures of the temperature-sensitive units. In order to demonstrate the feasibility of the correction method, the long-term outdoor temperature experiment is carried out. The multipoint temperature correction equations are obtained by using the least square regression method. The comparison results show that the measuring accuracy of the radiometer can be increased more effectively by using the multipoint temperature correction method.

Highlights

Microwave radiometers have been widely used in many remote sensing applications in recent decades [1,2,3]
During the long-term outdoor experiments, we found that the output of the solid-state noise source fluctuates with the environmental temperature changes, which causes measurement errors owing to the digital auto-gain compensation technique
The high-temperature point is the black body temperature and the low-temperature point is the clear sky brightness temperature collected from a weather station

Summary

Introduction

Microwave radiometers have been widely used in many remote sensing applications in recent decades [1,2,3]. In order to eliminate the effect of the noise and gain variations, many switched-type radiometers have been developed [7,8,9,10], e.g., the Dicke radiometer, the null-balancing Dicke radiometer, the two-reference temperature radiometer, etc All of these radiometers use negative feedback control and synchronous detection circuits, which add great complexity and cost to the systems. For this reason, the digital auto-gain compensation microwave radiometer (DGCMR) was proposed [11]. During the long-term outdoor experiments, we found that the output of the solid-state noise source fluctuates with the environmental temperature changes, which causes measurement errors owing to the digital auto-gain compensation technique. The multi-point temperature correction equations are deduced by using the least square regression method and the experiment results demonstrate the efficiency of the correction method

Radiometer Design and Temperature Correction Method

Temperature Experiment Results

Conclusions