Development of a New Detection Technique for the Ground Deformations associated with Volcanic Activity

该项目的基本目的是展示一种利用机载重复通过差分干涉合成孔径雷达（机载RP - insar）的新探测技术的效率和快速性，该技术可以准确探测与火山活动相关的群体变形，特别是在喷发序列中预期活动变化的情况下。在原理上，机载RP - insar的探测方法与卫星D-INSAR非常相似。然而，与卫星D-INSAR相比，实现机载RP -INSAR有几个额外的要求：(1)由于干涉基线条件的限制，x波段SAR系统的重复通过轨道精度通常必须在10米以内；(2)INSAR处理需要非常精确的天线运动数据，通常在每秒几毫米的精度范围内，等等。此外，对于正在进行的火山喷发活动，以及发生地震、边坡不稳定、地面隆起和下沉等其他地质事件，更需要一架相对较小的飞机来实现数据采集的快速响应能力和制造廉价的系统。为了克服这些要求，在常规GPS和惯性导航系统的基础上增加差分GPS导航系统以实现更精确的重复通过飞行控制，并在目标区域分布角反射器以获得足够的天线运动补偿数据。在埼玉县当地机场附近的Okegawa试验场的结果表明，如果在适当的天气条件下（中等风速和无雨），该系统是足够准确的。另一个试验场被选在福岛县阿祖马火山附近，那里的时间GPS测量显示，每天大约有几厘米的公里大小的块移动。实验结果表明，虽然需要在目标区域增加几个角反射器来增加地面控制点，但重复通过的轨道控制是足够精确的。该项目在世界上第一次显示了使用小型（螺旋桨）飞机进行机载RP - insar的有效适用性，尽管在该项目中进行的实验仅在中等天气条件下和一到两天的间隔中进行。然而，尽管在每一个程序中仍存在相当大的问题，以更清楚地证明这种方法的效率，但基本问题已经克服，结果足以进行下一步，即，这种方法需要适用于实际变形的领域，如东伊豆半岛和现在正在喷发的火山。少

Fundamental aim of this project is to demonstrate the efficiency and quickness of a new detection technique utilizing the Airborne Repeat-Pass Differential Interferometric Synthetic Apature Radar (Airborne RP D-INSAR) for obtaining an accurate detection of group deformations associated with volcanic activity, especially in case of anticipated activity changes during an eruption sequence. In principle, using the Airborne RP D-INSAR,the detection method is quite similar to the one in the satellite D-INSAR.There are, however, several additional requirements to realize the Airborne RP D-INSAR in comparison to the ones in satellite D-INSAR :(1) an accuracy of repeat-pass orbit must typically be within ten meters for the X-band SAR system due to the limitation of the interferometric baseline condition,(2) very precise antenna motion data, typically within a few millimeters accuracy in every seconds, are required for the INSAR processing, and so on.In addition, a relatively small aircraft is … More required to realize the capability of quick response for data acquisition and to make inexpensive system for the case of on-going eruptive activity, as well as other geological events such as the occurrence of earthquakes, unstable slope, upheaval and subsidence of the ground, and so on.In order to overcome these requirements, the differential GPS navigation system adding to the conventional GPS and INS (inertial navigation system) is installed for more accurate repeat-pass flight control and corner reflectors are distributed in the target area for obtaining the sufficient antenna motion compensation data.Results at the Okegawa test site near the local airport, Saitama prefecture, indicate that this system is accurate enough, if it were appropriate wether conditions (moderate wind speed and without rain).Another test site was chosen near the frank of Azuma volcano, Fukushima prefecture, where temporal GPS measurements have shown the movements of kilometer-size blocks of about a few centimeters per day. Results for this experiment showed that the repeat-pass orbit control is accurate enough, although it needs additional ground control points by adding several corner reflectors in the target area.This project has shown, for the first time in the world, the efficient applicability of using a small (propeller) aircraft for the Airborne RP D-INSAR,although the experiments made in this project were only performed in the moderate wether conditions and one or two day's interval.Although considerable problems would, however, remain in every procedure to demonstrate more clearly the efficiency of this method, the essential problems have overcome and results are enough to proceed to the next step, i.e., this method needs to apply to the actually deforming field such as east Izu peninsula and now erupting volcanoes. Less