Intelligent control, measurement and data processing in microwave scatterometer
B. Q. Zheng,H. Qin, X. Ao
Center for space science and Applied research
Academia Sinica, P.O. Box 8701,Beijing 100080 China
Abstract
This paper will describe a intellectualized airborne microwave scatterometer, Model LS-J, which adopts the computer control technique of the high speed microprocessor TMS 320 C25, to control measurement and data processing feasibly. It makes the scatterometer operation both simple and reliable, and the data are also accurate.
Introduction
Microwave remote sensing is a new subject, it has been more and more widely applied in army, agriculture, mining industry and ocean science. The microwave scatterometer is an active microwave sensor, it is used to measure the scattering conditions of the various terrain, the ocean wind, ice cover, soil humidity and so on. So, it provides important information to estimate the crop yield and to forecast the calamities. It can also be used to set up the scattering coefficient data rate to serve for the image radar.
First of all, we will briefly review the principle of the scatterometer, then discuss the necessity of intelligent control, measurement and data processing of the scatterometer, and lastly, introduce the implement of the intellectualized scatterometer Model LS-J.
Principal of Scatterometer
- Transmitter antenna sends a microwave beam to the detected terrain materials.
- Receiver antenna receives the backscattering factor of the terrain materials with the information of the detected terrain materials.
- This scatter factor is processed by the internal circuit to extract the information signal.
- The procedure of extracting a sample signal relating to transmitted wavebeam as the measured reference signal is called the internal calibration.
- Calculating the ratio of the information signal energy to the calibration signal energy and taking other system parameters into account to get the scattering coefficient of detected terrain materials.
According to the different working board, scatterometers are divided in two types: static and movable ones. The former is fixed on the static ground, motionless ship or helicopters, and adopts linear FM mode. The measured objects are relatively static. The latter is fixed on the moving automobiles, planes or satellites, adopts continuous-wave Doppler mode, measure the Doppler frequency shift caused by the relative moving objects.
They can be used to measure a wide area continuously. These two kinds of the scatterometers are developed by CAS/CSSAR have continuously and widely been used in practice. Among them Model RS-2 and RS-3 are fixed ground based one’s. The model LS-J is movable airborne one.
