3:00 PM - 3:15 PM
[STT48-06] Overview of the Advanced Land Observing Satellite-4 (ALOS-4) mission
★Invited Papers
Keywords:Synthetic Aperture Radar (SAR), Satellite, Remote Sensing, ALOS
We introduce the overview and current status of Advanced Land Observing Satellite-4 (ALOS-4) under development by Japan Aerospace Exploration Agency (JAXA). ALOS-4 is an earth observation satellite equipped with an L-band synthetic aperture radar (SAR) which Japan has developed for three generations of satellites, JERS-1, ALOS and ALOS-2. The mission objectives of ALOS-4 are as follows,
(1) Highly accurate monitoring of ground deformation and subsidence for not only a posterior damage assessment but also detecting anomalies at an early stage. Observation frequency throughout Japan should be increased from about 4 times/year by ALOS-2 to more than 20 times/year by developing technologies for wide-area and high-resolution observation.
(2) Continuation and enhancement of the ALOS-2 mission such as all-weather disaster monitoring, forest monitoring, sea ice monitoring, and ship and ocean monitoring, and also exploring new applications such as monitoring of large infrastructures.
To achieve these objectives, new technologies are adopted for ALOS-4 that greatly improve its functions and performances compared to ALOS-2. Table 1 shows the comparison of the main specifications of ALOS-4 and ALOS-2. The L-band SAR system (PALSAR-3) increases the observation swath width while keeping the resolution and image quality of ALOS-2 by receiving several beams simultaneously using Digital Beam Forming (DBF). PALSAR-3 has three types of observation modes: Spotlight mode, Stripmap mode (3/6/10 m resolutions), ScanSAR mode, and the performance of the major observation modes often used in ALOS-2 are as shown in Table 2. To remove ionospheric disturbances in Interferometric SAR (InSAR) analysis, a new mode for observing two separated frequency bands in the L-band 84 MHz is provided. Besides the SAR system, there are many new developments for the satellite systems such as high-speed data downlink, large capacity of data recorder, improvement of orbit determination accuracy, and extended design life. The same orbit and observation geometry as ALOS-2 are selected to provide the InSAR capability between ALOS-2 and ALOS-4 data and the high continuity of user’s applications developed for ALOS-2, and long-term analysis capability over 10 years. As of February 2018, ALOS-4 is in the detailed design phase, and launch of the satellite is planned in JFY2020.
(1) Highly accurate monitoring of ground deformation and subsidence for not only a posterior damage assessment but also detecting anomalies at an early stage. Observation frequency throughout Japan should be increased from about 4 times/year by ALOS-2 to more than 20 times/year by developing technologies for wide-area and high-resolution observation.
(2) Continuation and enhancement of the ALOS-2 mission such as all-weather disaster monitoring, forest monitoring, sea ice monitoring, and ship and ocean monitoring, and also exploring new applications such as monitoring of large infrastructures.
To achieve these objectives, new technologies are adopted for ALOS-4 that greatly improve its functions and performances compared to ALOS-2. Table 1 shows the comparison of the main specifications of ALOS-4 and ALOS-2. The L-band SAR system (PALSAR-3) increases the observation swath width while keeping the resolution and image quality of ALOS-2 by receiving several beams simultaneously using Digital Beam Forming (DBF). PALSAR-3 has three types of observation modes: Spotlight mode, Stripmap mode (3/6/10 m resolutions), ScanSAR mode, and the performance of the major observation modes often used in ALOS-2 are as shown in Table 2. To remove ionospheric disturbances in Interferometric SAR (InSAR) analysis, a new mode for observing two separated frequency bands in the L-band 84 MHz is provided. Besides the SAR system, there are many new developments for the satellite systems such as high-speed data downlink, large capacity of data recorder, improvement of orbit determination accuracy, and extended design life. The same orbit and observation geometry as ALOS-2 are selected to provide the InSAR capability between ALOS-2 and ALOS-4 data and the high continuity of user’s applications developed for ALOS-2, and long-term analysis capability over 10 years. As of February 2018, ALOS-4 is in the detailed design phase, and launch of the satellite is planned in JFY2020.