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差动干涉合成孔径雷达(机载RPD-InSAR)对与火山活动有关的群体变形进行准确检测的新探测技术的效率和快速性，特别是在喷发序列期间预期活动变化的情况下。在原理上，使用机载逆合成孔径雷达的探测方法与星载逆合成孔径雷达的探测方法非常相似。然而，与星载逆合成孔径雷达相比，实现机载逆合成孔径雷达有几个额外的要求：(1)由于干涉基线条件的限制，对于X波段合成孔径雷达系统，重复轨道的精度通常必须在10米以内；(2)对于干涉合成孔径雷达系统，需要非常精确的天线运动数据，通常在每秒几毫米的精度内，等等。此外，相对较小的飞行器是…为了更好地实现数据采集的快速响应能力，以及对正在进行的喷发活动以及地震、斜坡不稳定、地面隆起和下沉等地质事件的情况，更需要实现廉价的系统。为了克服这些要求，在常规GPS和INS(惯性导航系统)的基础上，安装了差分GPS导航系统，以实现更准确的重复飞行控制，并在目标区域布置角点反射器，以获得足够的天线运动补偿数据。在崎玉县当地机场附近的小川试验场的测试结果表明，该系统具有足够的精度，如果天气条件合适(风速适中，没有降雨)，另一个试验点被选在福岛县Azuma火山的弗兰克附近，那里的临时GPS测量显示，千米大小的地块每天移动约几厘米。实验结果表明，重复通过轨道控制是足够精确的，尽管它需要通过在目标区域增加多个角反射器来增加地面控制点。该项目首次在世界上证明了使用小型(螺旋桨)飞机进行机载RP D-InSAR的有效适用性，尽管本项目所做的实验只在温和天气条件下进行，间隔一到两天。尽管在每个过程中仍然存在相当多的问题，以更清楚地证明该方法的有效性，但基本问题已经被克服，结果足以继续进行下一步，即，这种方法需要应用于实际变形的领域，如伊豆半岛东部和现在正在喷发的火山。较少

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