Masato Ohki

Deorientation Effect Investigation for Model-Based Decomposition Over Oriented Built-Up Areas

Deorientation processing has been incorporated into model-based decomposition to cure the overestimation of volume scattering contribution, by rotating the coherency matrix to minimize the cross-polarization term. First, the derivation of the rotation angle is clarified for avoiding the ambiguity. Moreover, even with the implementation of deorientation processing, oriented built-up areas with large orientation angles are still misjudged as volume scattering dominant. Further to the investigation of the deorientation effect, we focus on oriented built-up patches. A parameter, named dominant polarization orientation angle (DPOA), is introduced to label each patch. The behavior of the deorientation on coherency matrix and model-based decomposition over purely oriented built-up areas with respect to DPOA is disclosed. Experimental studies from the Advanced Land Observing Satellite/Phased Array type L-band Synthetic Aperture Radar (ALOS/PALSAR) polarimetric SAR data set demonstrate that model-based decompositions with deorientation work well for oriented built-up areas when |DPOA| ≤ 22.5°. However, for large |DPOA| (e.g., |DPOA| >; 22.5°), even with the deorientation processing, for the conventional decompositions which assume that only the volume scattering contributes to the cross-polarization term, the decomposed volume scattering power may also be dominant even for purely oriented built-up areas. Thereby, misinterpretation still occurs, motivating further advancements.

SAR interferometry using ALOS-2 PALSAR-2 data for the Mw 7.8 Gorkha, Nepal earthquake

The Advanced Land Observing Satellite-2 (ALOS-2, “DAICHI-2”) has been observing Nepal with the Phased Array type L-band Synthetic Aperture Radar-2 (PALSAR-2) in response to an emergency request from Sentinel Asia related to the Mw 7.8 Gorkha earthquake on April 25, 2015. PALSAR-2 successfully detected not only avalanches and local crustal displacements but also continental-scale deformation. Especially, by the use of the ScanSAR mode, we are able to make interferograms that cover the entire displacement area of the earthquake. However, we did encounter some fundamental problems with the ScanSAR and incorrect settings of PALSAR-2 operation that have now been fixed. They include (1) burst overlap misalignment between two ScanSAR observations, which limits the number of pairs available and the quality of the interferogram, (2) non-crustal fringes which are derived from co-registration error and/or ionospheric effect and, (3) incorrect setting of the center frequency in the Stripmap beam F2-6. In this paper, we describe their problems and solutions. The number of interferometric pairs are limited by (1) and (3). The accuracy of the interferograms are limited by (2) and (3). The experimental results showed that current solutions for (2) and (3) work appropriately.

ALOS-Next/TanDEM-L: A highly innovative SAR mission for global observation of dynamic processes on the earth's surface

ALOS-Next/Tandem-L is a proposal for a highly innovative L-band SAR satellite mission for the global observation of dynamic processes on the Earths surface with hitherto unparalleled quality and resolution. It is based on a collaboration between DLR and JAXA which started with a pre-phase A study in 2013 and is currently undergoing a phase A study. Thanks to the novel imaging techniques and the vast recording capacity with up to 8 Tbytes/day, it will provide vital information for solving pressing scientific questions in the biosphere, geosphere, cryosphere, and hydrosphere. By this, the new L-band SAR mission will make an essential contribution for a better understanding of the Earth system and its dynamics. ALOS-Next/Tandem-L will, moreover, open new opportunities for risk analysis, disaster management and environmental monitoring by employing especially designed acquisition modes and techniques in combination with a reconfigurable tandem satellite configuration and an L-band SAR instrument with advanced digital beamforming techniques.

ALOS-2 operation status

The Advanced Land Observing Satellite-2 (ALOS-2) was successfully launched on 24th May, 2014. The mission sensor of ALOS-2 is the Phased Array type L-band Synthetic Aperture Radar-2 called PALSAR-2 which is the state of the art L-band SAR system. At After launch, the initial checkout and the calibration and validation phase had been completed, and the PALSAR-2 standard products were released via web site at the end of November 2015. Until now, ALOS-2 has had contributed to a lot of emergency observations for disasters such as earthquakes flood, land slide which were impacted by typhoons, and volcano eruptions, not only in Japan but also in the world. Furthermore, based on the Basic Observation Scenario (BOS) of ALOS-2, base map data are collected and archived for the interferometry SAR processing in Japan area as well as global world. This document describes the results of ALOS-2 operation in routine operation phase.

Emergency observation and disaster monitoring performed by ALOS-2 PALSAR-2

One of the main missions of the Advanced Land Observing Satellite-2 (ALOS-2, “DAICHI-2” ) is the disaster monitoring. Japan Aerospace Exploration Agency (JAXA) has operated the emergency observation more than hundred times in 2015. Not only the most important event in 2015, the Mw 7.8 Gorkha earthquake on April 25, the Phased Array type L-band Synthetic Aperture Radar-2 (PALSAR-2) aboard ALOS-2 observed various floods, volcano eruptions and earthquakes. In this paper, we present some emergency observation results which were impossible to be performed by the previous ALOS. That is, automatically burst aligned ScanSAR to ScanSAR interferometry and, left / right looking for increasing acquisition opportunity.

Evaluation of detection capability of crustal movement by airborne SAR (PI-SAR-L2) repeat-pass interferometry

This paper reports the evaluation results of detection capability of crustal movement by an airborne SAR (Pi-SAR-L2) repeat-pass interferometry. Pi-SAR-L2 belongs to by JAXA (Japan Aerospace Exploration Agency). The object is to estimate the detection accuracy of crustal movement by Pi-SAR-L2.

PALSAR-2 polarimetric image mosaic and its application to land cover monitoring

Land cover is an important earth observation parameter for understanding the Earths ecosystem. Compared with optical sensors, Synthetic Aperture Radar (SAR) enables more rapid land cover monitoring with its all-weather, day-and-night imaging capability. We mosaicked 390 scenes of PALSAR-2 fully polarimetric data acquired in Japan and computed several polarimetric decompositions. Then, we applied supervised land-cover classification. The accuracy of seven categories classification in the Kanto region, Japan, was 75.0%.

Performance of ALOS-2 PALSAR-2 for disaster response

In 2016, the Advanced Land Observing Satellite-2 (ALOS-2, “DAICHI-2”) observed various disaster affected areas. Japan Aerospace Exploration Agency (JAXA) operated the emergency observation more than hundred times in the year. The Phased Array type L-band Synthetic Aperture Radar-2 (PALSAR-2) aboard ALOS-2 contributed for detecting the disaster affected area, ground deformation and flood affected area. Especially for the ground deformation and damaged area detection caused by the devastating earthquakes in 2016, e.g., Kumamoto earthquakes in Japan and Kaikoura earthquake in New Zealand, researchers provided variable analytical results from ALOS-2 observation data. In this paper, some examples of the emergency observation results are presented.

Accuracy improvement by residue and amplitude based local co-registration method for ALOS-2/PALSAR-2 DInSAR

In the field of Synthetic Aperture Radar (SAR) interferometry, we generally expect that there is only unique dominant scatterer in one pixel. To make a SAR interferogram, we have to observe a place twice. The dominant scatterer in every pixel must be identical in those observations. However, in an actual situation, there are multiple scatterers in one pixel physically, and the dominant one may be changed in the two observations. Slight difference of incident angle may cause the change of the dominant scatterer and the propagation path. The change can generate singular points (SPs) in the inter-ferogram which prevent us from accurate phase unwrapping. Here, we present experimental results in an anechoic chamber which show the mechanism of the singular point generation.

Development of new multi-band equatorially orbiting POLinSAR satellite sensors system configurations for varying latitudinal coverage within total tropical belt: Invited group presentation for establishing an associated Consortium

The relevance of this challenging still unresolved development of multi-band equatorially orbiting fully polarimetric POLinSAR satellite configurations to the entire terrestrial globe will be highlighted. Special attention will be given to generation of global weather phenomena, supply of an ever more relevant stable food base, extraction of mineral and energy resources with its implicit local environmental deterioration, and of more successfully securing bio-diversity. All of these daunting natural hazards of top international priority should justify the immense financial resources required for pursuing this timely and urgently to be realized proposal. In retrospect, collaboration with additional international National Research Centers involved in advancing multi-band POLinSAR satellite sensors is sincerely desired and so is the financial support from our national, regional and international governmental sponsors - foremost the United Nations. The proposer (author) and dedicated collaborators consider APSAR-2015 to be the ideal forum for introducing this timely proposal, well suited for the Lead-Session of Space- & Air-borne SAR Systems and Missions.