Study on satellite radar interferometry

最近对卫星雷达干涉测量的研究已经证明了绘制南极洲三维地形、地震或冰盖流动引起的位移场的能力。然而，为了得到精确的测量结果，需要具有厘米级精度的精确基线，水汽对距离延迟的影响是不可忽视的。本研究的目的是通过使用角反射器(CRS)的实验和对日本地球资源卫星的L波段合成孔径雷达数据的干涉分析，来研究卫星雷达干涉测量的能力。对于具有较大雷达反射的CR，从CRS中检测到的位移精度为L厘米，有意位移为6厘米和10厘米。对于一般地表，在干涉图上观测到了等效位移大于1厘米的局部和较大的位相变化。可能的原因是地表条件的时间变化。为提高大面积干涉相位测量的精度，提出了干涉仪基线估计方法。利用气象观测站的观测资料(气压、温度和水汽气压)和数字高程模型，建立了绘制大气中水汽引起的距离延迟的方法。分析表明，水汽对雷达干涉图的影响较大，因为研究区地形高度变化较大，且部分干涉组合来自不同季节(即夏季和冬季)。

Recent studies on satellite radar interferometry have demonstrated the capability of mapping of 3-D terrain, displacement fields caused by earthquakes or ice sheet flow in the Antarctica. However, it is pointed out that in order to derive fine measurements, accurate baselines with cm order accuracy are required and that influences of water vapor on range delays are not negligible. An objective of this study is to investigate a capability of satellite radar interferometry through experiments using corner reflectors (CRs) and interferometric analysis of L-band synthetic aperture radar data with the Japanese Earth Resources Satellite. As for a CR that has a large radar reflection, detection of a displacement of l-cm accuracy was demonstrated from CRs with intentional 6-cm and 10-cm displacement. As for general land surfaces, local and large phase variations whose equivalent displacement is more than 1-cm were observed over interferograms. Possible reason is temporal change of surface conditions. To improve an accuracy of interferometric phase measurement over large areas, the method to estimate interferometer baseline was advanced. The method to map range delays due to water vapor in the atmosphere was developed using observation data (Air presser, temperature and water vapor presser) at meteorological observatories and digital elevation model. Analysis shows water vapor has a great influence on the radar interferograms, because there exists a large terrain altitude change over the study area and some interferometric combinations are from different seasons (i.e. summer and winter).