Current Status of Developing ALOS-4 with Key Missions - Palsar-3 and SPAISE3.

Japan is a geographically active region which experiences natural disasters such as earthquakes, floods, and volcanic activities. Thus, Japan has developed advanced world leading disaster prevention technology utilizing space applications. Especially, the Japanese ALOS series satellites target for prevention and mitigation of natural disasters. The Advanced Land Observing Satellite-4 (ALOS-4) is a successor of ALOS-2. Key components such as Phased Array type L-band Synthetic Aperture Radar (PALSAR-3) and Space based Automatic Identification System Experiment (SPAISE3) are based on improved designs from PALSAR-2 and SPAISE2 of ALOS-2. The missions of ALOS-2/4 are to observe the change of geographical conditions regarding before and during natural disasters along with monitoring signals sent from ships on the ocean. PALSAR-3 enables observation throughout the day and night by microwave radar technologies. The L-band SAR can observe the ground through leaves and branches by using long wavelengths, therefore it enables close observation of changes on ground surface. SPAISE3 serves an important role to detect AIS signals from ocean vessels specifically to identify congested oceanic traffic areas of ships. These components are introduced in this paper. ALOS-4 is currently in the integration phase for each completed component with testing of the integrated satellite system having commenced.