Research

Innovative Microwave Remote Sensing

Innovative Microwave Remote Sensing

Josaphat Tetuko SRI SUMANTYO

Professor of Center for Environmental Remote Sensing (CEReS), Chiba University

He was born in Bandung, Indonesia. He graduated Kanazawa University, and then received MS degree in 1997 from Graduate School of Electrical and Computer Engineering, Kanazawa University. Ph.D at Graduate School of Science and Technology, Chiba University in 2002. He joined Center for Frontier Electronics and Photonics, Chiba University from 2002 until 2005, as a lecturer. Assistant professor at Center for Environmental Remote Sensing, Chiba University in 2005, and since 2013, full professor. His research field is micro wave remote sensing and Circularly Polarized Synthetic Aperture Radar (CP-SAR) sensor.

Observation of disaster monitoring and crop monitoring using 'electromagnetic waves going through clouds

Do you know what kind of technology remote sensing is? It is the technology to obtain information about a target by using electromagnetic waves from the target. The used electromagnetic wave ranges from visible light and infrared to microwave by its wavelength. Among these, microwave has a special feature; it can go through clouds. That is, land surface can be observed from a satellite by microwave even on cloudy day . The main type of microwave remote sensing is a Synthetic Aperture Radar (SAR). SAR generates microwave signal, transmits it to the target direction, and receives scattered microwave signal from the target sequentially along with the movement of SAR. It is possible to obtain a high-resolution observed image by combining these scattered signals. One of advantages of SAR is the ability to detect change of distance between SAR and a target by using two SAR images observed before and after the change such as earthquake, land slide, or land subsidence. The objective of this research is to develop small SAR with high performance, to launch a small satellite with the developed SAR, and to apply the observed data to disaster monitoring, management of infrastructure, and crop monitoring. The SAR sensor can detect changes of distance between the SAR and the object. So, it is possible to observe changes of the ground surface such as crustal movements, building collapse, land subsidence, and volcanic activity. There is also a possibility to detect crop conditions by a new type of developed SAR (circularly polarized synthetic aperture radar: CP-SAR) which can observe orientation of target surface. Another use of microwave is the one transmitted from the GPS. It can also be used for observation of the electron density of the ionosphere, 100-700 km above the ground, by using a microwave delay information. By analyzing the relationship between the electron density and the earthquake, the research to predict earthquake is also planned. The effectiveness of the newly developed circularly polarized synthetic aperture radar (CP-SAR) will be evaluated by the observation experiment mounted on the aircraft Boeing 737-200. In addition, the experiment using unmanned aerial vehicle (UAV) is scheduled. In parallel, the preparation to launch a small satellite equipped with the CP-SAR within five years, is going on. The cooperated and harmonized operation (called as a constellation) of five small satellites by Indonesia, South Korea, Malaysia, etc. is planned. It will increase the observation frequency, and can be used for disaster prevention and monitoring in the future.

Development of the world's first 'small' and 'new' radar

This study is to develop the ingenious synthetic aperture radar (SAR) and to apply it to practical use. It is 'small' and 'new'; its weight is 1/5 to 1/10 of the conventional SAR. This is an absolute ideal condition for mounting it in small satellite. The small satellite can be launched by less than 1/10 cost than ever. Thanks to this low cost, we can increase the observation opportunity by operating a plurality of satellites at the same time. In addition, the 'new' type of SAR, circularly polarized synthetic aperture radar (CP-SAR) which emits a microwave with a rotating the electric field plane, can obtain data with less noise. We aim to achieve the world's first small satellite equipped with SAR by this study. As the next step, we plan to realize satellite constellation, that is five small satellites equipped with SAR will be launched and operated integrated manner in cooperation with Korea (KARI), Taiwan (NSPO), Indonesia (LAPAN), USA (NASA), and Europe (ESA). This enables to increase observation opportunities, and it can contribute todisaster prevention and monitoring. In the long term plan, daily observation of a limited region such as Japanese islands from 10-20 km above the ground by stratospheric platform with SAR will be available.

Message to students and young researchers

I hope many students will come to participate in new research field, remote sensing. Remote sensing is a broad field from sensor development (hardware) to the data processing analysis (software), and from basic science to analyze the observed object (environment) to practical science to apply obtained information to society. The word "global" can express the feature of this field. First, the observed targets are located in many countries. Secondly, the study is performed by global cooperation with many countries. More and more overseas students are studying remote sensing at CEReS, Chiba University. You can do the research of the world's most advanced remote sensing at Chiba University.

Vehicle mounting SAR system

Detected result of exterior-wall damages using the SAR backscatter changes

Spreading mechanism of SAR antenna

Illustration of the observation by small satellite mounting SAR system

Development schedule of small satellite mounting SAR system

Josaphat Laboratory Experimental Unmanned Aerial Vehicle (JX-2)