ALOS-4: Enhancing Disaster Prevention Through Radar-Based Remote Sensing

ALOS-4: Enhancing Disaster Prevention Through Radar-Based Remote Sensing

   On July 1, 2024, the Japan Aerospace Exploration Agency (JAXA) successfully launched the ALOS-4 (Advanced Land Observing Satellite 4) mission, also known as Daichi 4, into sun-synchronous orbit aboard the H3 rocket from the Yoshinobu Launch Complex.

   ALOS-4, a 3,000 kg satellite manufactured by Mitsubishi Electric, is Japan's latest remote sensing satellite designed to monitor ground-based environmental changes using synthetic aperture radar (SAR). This crucial information aids in disaster prevention and enhances disaster management efforts.

   The satellite was manufactured by Mitsubishi Electric, with a total mass of 3,000 kg. ALOS-4 operated at an altitude of 628 kilometers in the sun-synchronous orbit, equipped with two instruments aboard, the PALSAR-3 (Phased Array Type L-band Synthetic Aperture Radar-3) and the SPAISE3 (SPace-based AIS Experiment 3rd).

   The ALOS-4 mission is to continue the work from the ALOS-2 satellite, which began its operation in 2014, with the PALSAR-3 being the successor to the PALSAR-2 radar aboard ALOS-2, increasing its observation swath from 50 km to 200 km, while still providing the same quality of resolution.

   Apart from the wider observation swath, the ALOS-4 satellite will perform more frequent observations of the active volcanoes, which are linked to diastrophism, or ground transformation caused by volcanic activity. The ALOS-2 can be observed once every two weeks, drastically improving from just 4 times a year with the ALOS-2 mission.

   Radar images can be obtained both during daytime and nighttime, this makes the ALOS-4 satellite capable of making a continuous observation, using its onboard phased array type L-band synthetic aperture radar, known as the PALSAR-3. This mission can continue to monitor ground transformation without worrying about weather since radio waves can penetrate through clouds.

   Moreover, data obtained from the ALOS-4 mission can also be used to monitor deforestation at a higher resolution than from the ALOS-2 satellite, this will contribute to improved forest monitoring globally. JAXA also planned to use data from its latest mission to detect the structure displacement of dams, port facilities, and many more from deterioration. This can be done with PALSAR-3's precision of a few millimeters and detailed observation as the satellite passes above the selected area more frequently.

   During a disaster, the ALOS-4 satellite can serve as a space-based data provider for disaster response and management. This was demonstrated with the ALOS-2 observation of the Noto Peninsula during its earthquake in January 2024. With the improved capability of PALSAR-3 radar, ALOS-4 can conduct a detailed observation with a broader width of the area covered in one single pass, thus improving the data to be used for government and essential worker's disaster response plans.