System design of wide swath, high resolution, full polarimietoric L-band SAR onboard ALOS-2

This paper describes SAR system design of the Advanced Land Observing Satellite-2 (ALOS-2), which is a next-generation Japanese L-band SAR satellite. Since one of an important mission of ALOS-2 is a global monitoring using its unique frequency of L-band, a capability of wider coverage is required. On the contrary, in the point of disaster monitoring especially for urban area, relatively higher spatial resolution is essential. To comply with such a contradictive requirement of wide swath and high resolution, ALOS-2 utilizes a dual-receive channel (DRC) technique, and achieved a coverage area of up to 50km with a spatial resolution of down to 3m. In the paper, the H/W design of ALOS-2 DRC mode is explained. For a wider coverage of polarimetric observation, ALOS-2 installs the fully redundant and “quad-receive channel” system to full-polarimetric mode, achieving a maximum coverage of 50km at 6m resolution. As an experimental mode, new polarimetric mode called “compact polarimetry” is installed for a wide coverage of polarimetric observation.

1. INTRODUCTION

The Advanced Land Observing Satellite-2 (ALOS-2) is a next-generation Japanese SAR satellite. As a successor of ALOS/PALSAR, The SAR sensor onboard ALOS-2, named “PALSAR-2”, follows its unique frequency of L-band. Considering a uniqueness of the land in Japan, continuous investigation of the forest, volcanoes, and earthquake activities, based on differential interferometric SAR (DInSAR) and/or polarimetric techniques, become important missions of ALOS-2. In order to conduct continuous investigation by InSAR/DInSAR, acquisition of a base map, including both domestic and global mapping, is indispensable. An L-band sensor is hence required for wide observation width in order to acquire the reference data as much as possible for a short period of time. In a different viewpoint, a demand of the detailed information before and behind the disaster, e.g. East Japan great earthquake, is also increasing. In this case, a finer spatial resolution is preferred. From this viewpoint, surveillance in Japan and the whole world of 3m-class is planned in ALOS-2 mission. To realize a demand of these both sides more efficiently, broadening while maintaining 3m-class high resolution becomes indispensable.