Terahertz reflectance spectrum is widely used in material thickness measurement, material composition detection and other aspects. However, the reflection wave is easily affected by the surface roughness produced in the process of material processing, resulting in noise and measurement error. In this paper, the terahertz reflection model of three-layer medium is derived, and the relationship between smooth surface and rough surface is established by Kirchhoff approximation theory. Secondly, the terahertz reflection spectrum and frequency spectrum of aloe emodin were measured by THz-TDS(terahertz-time domain spectral system). By introducing controllable roughness surface with sandpaper of different specifications, the reflection spectrum of roughness of each specification surface was measured, the reflectance corresponding to different frequencies was calculated, and the reflection spectrum of smooth surface was compared and analyzed. The influence of these results on the ability of THz reflection spectrum to detect Chinese medicinal herbs was discussed. In addition, by introducing Kirchhoff approximation, the reflection spectrum relation model of rough surface and smooth surface is established to compensate the reflection spectrum of rough surface. It is found that the power of reflection spectrum can be improved to some extent and the influence of rough surface on reflection spectrum can be reduced.
Spaceborne microwave radiometer is nowadays one of the most important means in earth observation and space
exploration. It plays an important role in the remote sensing application because of its all-day, all-weather observation
capability for earth surface observation and atmospheric sounding. Calibration is the basis of quantitative application,
and calibration precision is the integrated result of several instrument performances, such as sensitivity, stability and so
on. As a result, it is important to analyze the effects of the concerned factors which affect the calibration precision. In this
paper, Orthogonal Array Test Design Method is used to theoretically analyze how the transmission parameters of the
calibration system contribute to the calibration uncertainties. Based on the result, some suggestion is proposed to the
design of a spaceborne radiometer calibration system.
An airborne multi-function microwave remote sensing system has been developed in order to verify the design and performance of future Chinese spaceborne system. Future Chinese spaceborne microwave remote sensing system is for ocean research, atmosphere research and soil moisture content monitoring. Like spaceborne system, the airborne system also includes altimetry, scatterometry and radiometry functions. There are five operate modes: altimetry mode, scatterometry mode, radiometry mode, altimetry and radiometry mode, scatterometry and radiometry mode. The operate mode can be changed by program. There are five channels in radiometry mode. The altimetry mode, the scatterometry mode and the second channel of radiometry mode operate at the same Ku band. In the airborne system, the scatterometry mode uses two pyramidal horn antennae. One is for horizontal polarization. The other is for vertical polarization. The horizontal polarization antenna is also used in the altimetry mode. The radiometry mode uses five pyramidal horn antennae.
Flight experiments have been conducted on southern sea of China. The results verify the design and performance of the airborne multi-function microwave remote sensing system. They also show that the design of future Chinese spaceborne system is practicable. In this paper, the principle of airborne system is briefly introduced. Flight experiments and results are described.
In microwave remote sensing, if we want to acquire active and passive remote sensing information of an object simultaneously, we usually measure it with a scatterometer and a radiometer at the same time. Because two remote sensors are used, the experiment is very complicated. A scattero-radiometer is developed in order to reduce remote sensor cost and experiment difficulty. This scattero- radiometer consists of a continuous wave scatterometer and a digital gain compensation radiometer. In this paper, the block diagram and the timing program of this scattero- radiometer are detailed submitted. Performance test show that the scattero-radiometer not only remains original performance of a scatterometer and a radiometer, but also is able to measure backscattering coefficient and brightness temperature simultaneously. It is more fit for acquiring active and passive microwave remote sensing information simultaneously.
The types and technology performance of multi-frequency microwave radiometers designed and developed from 1973 are briefly introduced. Some images and data for land and sea surface by our multi-frequency microwave radiometers are given. Technology foundation of developing spaceborne microwave radiometers and space systems for monitoring natural disasters in China is discussed.
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