【作者】 白伟华；

【导师】 朱光武；

【作者基本信息】 中国科学院研究生院（空间科学与应用研究中心） ， 空间物理学， 2008， 博士

【摘要】 全球卫星导航定位系统(GNSS)除了传统的导航和定位作用外,还可以利用其反射信号提取海洋表面地球物理信息。本文对利用GNSS海洋反射信号(GNSS-R)反演海面要素的理论和方法进行了详细讨论。论文首先详细说明了GNSS-R的研究现状,然后在海面高度服从正态分布,海面反射满足基尔霍夫散射近似条件的假设前提下推导了GNSS信号海面散射系数,建立GNSS-R信号的功率波形与海面散射几何和海面粗糙度(使用海面均方坡度来描述)等因素的关系。采用了Elfouhaily模型来求解海面均方斜度,进而建立了GNSS-R反演海面风场的理论模型,同时也是空基和星载GNSS-R反演海面高度再跟踪处理的理论模型。对等码距环、等多普勒区域和闪烁区域的形状和大小进行了详细讨论。文中系统地阐述了GNSS-R海面风场遥感的原理和方法,以及反演流程,介绍了几个反演海面风场的例子,试验表明GNSS-R反演海面风场精度约为2m/s和20°。GNSS-R反演高度主要有两种方法,一种是利用直接信号和反射信号的码延迟来测高,另一种利用载波相位来测高。利用码延迟来测高的方法比较稳健而且适用于地面、空基和星载等各种情况,所以本文详细阐述了在不同接收机高度下利用码延迟反演测高的方法。通过岸基小麦岛试验(结果精度为5分钟平均高度RMS为39cm)和空基Eddy试验(结果精度在20km范围内高度RMS为10cm,均值偏差为2cm)举例阐述了码延迟测高的方法和精度。在小麦岛岸基试验的基础上,国内首次开发了GNSS-R的软件接收机预处理程序,为进一步的GNSS-R海洋遥感研究奠定了基础。此外,文中还研究了LEO(低轨卫星)星载GNSS-R技术的时间和空间分辨率和利用该技术探测和预警海啸的可能性。GNSS-R技术作为一种新型的遥感手段还在不断的完善中,因此,在文章最后提出了下一步的工作设想。更多还原

【Abstract】 In this thesis,the technique of using GNSS-R signals to extract ocean surface geophysical information has been discussed in detail,It is an alternative purpose of the GNSS other than navigation or positioning that brings about an unprecedented source of data in the field of ocean remote sensing.The history of GNSS-R research is introduced in advance. On the assumption which the distribution of the sea surface height is Gaussian and the surface reflection is satisfied with the limit of the Kirchhoff Geometric Optics approximation, scattering cross-section coefficient is derived and a theoretical GNSS-R signal power waveform model has been developed which is depended on GNSS-R scattering geometry, sea surface roughness (characterized by mean-square slope) and so on. In order to calculate the mean-square slope, the Elfouhaily Model have been introduced, therefore, a theoretical model has been derived to retrieve wind field ,which can also be used for retracking in the airborne and space-borne altimetry applications by using GNSS-R signals. Furthermore, the shape and size of the iso-range annuli, iso-Doppler stripes and glistening zone have been discussed in details.The theoretical model and the method to inverse sea surface wind have been expatiated systemically by using microwave scattering theory and sea spectra, and the retrieve flow-chart , block diagram and operating principle has been discussed. Several retrieved examples have been introduced, which shows that the retrieval accuracys of wind speed and direction are about 2m/s and 20o respectively.Altimetry in GNSS-R can be carried out in two general ways, depending on the ranging principle used. In code altimetry, the code is used for ranging with the direct and reflected signals. In phase altimetry, the phase is used. Because Code altimetry is robust and applicable for ground-borne, air-borne and space-borne applications, the inverse methods are addressed in different receiver heights. Accuracy in code altimetry was demonstrated during the coastal Xiao Mai island Experiment (the results RMS error of the 5 minutes averaged GNSS-R absolute altimetric solution was of 39 cm) and the airborne Eddy Experiment (the results RMS error of the 20 km averaged GNSS-R absolute altimetric solution with respect to Jason-1 and GPS buoy measurements was of 10 cm, with a 2 cm mean difference). Base on the coastal experiment, the GNSS-R software receiver pre-processing algorithm is developed, which lays solid foundation for the futher research of oceanographic remote sensing. Furthermore, the potential capability of coverage and time-space resolution by GNSS-R from Low Earth Orbiters (LEOs) is studied, and the applicability of the space-borne GNSS-R to detect tsunami is discussed.As a new remote sensing tool, the GNSS-R technique is imperfect and developing, so the future work has been outlined in the end of the text.更多还原