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Advanced Land Observing Satellite (ALOS)

The Advanced Land Observing Satellite "DAICHI" (ALOS) was developed to contribute to the fields of mapping, precise regional land coverage observation, disaster monitoring, and resource surveying. It enhances land observation technologies acquired through the development and operation of its predecessors, the Japanese Earth Resource Satellite-1 (JERS-1, or Fuyo) and the Advanced Earth Observing Satellite (ADEOS, or Midori). ALOS has three sensors: the Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM), which is comprised of three sets of optical systems to measure precise land elevation; the Advanced Visible and Near Infrared Radiometer type 2 (AVNIR-2), which observes what covers land surfaces; and the Phased Array type L-band Synthetic Aperture Radar (PALSAR), which enables day-and-night and all-weather land observation.

DAICHI's remote-sensing equipment enables precise land coverage observation and can collect enough data by itself for mapping on a scale of 25,000 to 1. without relying on points of reference on the ground. It is expected to play an important role in cartography by providing maps of Japan and other countries, including those in the Asia-Pacific region, which is one of ALOS's main objectives. Other objectives include regional observation for harmonization between the environment and development on Earth, domestic and overseas disaster monitoring and resource surveys.

Its contributions to the mitigation of environmental destruction and natural disasters made it an essential satellite for our future. It was launched by the H-IIA launch vehicle No.8 from the Tanegashima Space Center (TNSC) in January 24, 2006. After being in operation for three years of its designed life, it further worked for an extended period over its target period of five years. However, on April 22, 2011, a power generation anomaly caused a communication loss. At 10:50 a.m. on May 12, 2011, JAXA sent a command to stop the onboard transmitter and batteries of the DAICHI from the ground station to complete its operation.

ALOS-2 - Radar

The Advanced Land Observing Satellite-2 (ALOS-2), a Japanese satellite, also known as DAICHI-2, was launched in 2014 by the Japan Aerospace Exploration Agency (JAXA). Technologies acquired from the DAICHI operation were succeeded to the second Advanced Land Observing Satellite “ALOS-2.” The Advanced Land Observing Satellite-2 (ALOS-2) was a follow-on mission from the "DAICHI", which contributed to cartography, regional observation, disaster monitoring, and resource surveys. ALOS-2 will succeed this mission with enhanced capabilities.

Specifically, JAXA conducting research and development activities to improve wide and high-resolution observation technologies developed for DAICHI in order to further fulfill social needs. The state-of-the-art L-band Synthetic Aperture Radar-2 (PALSAR-2) aboard ALOS-2, which is an active microwave radar using the 1.2GHz frequency range, will, in responding to society's needs, have enhanced performance compared to DAICHI/PALSAR. The PALSAR-2 is capable of observing day and night, and in all weather conditions.

ALOS-2 had a spotlight mode (1 to 3m) and a high resolution mode (3 to 10m), whilst PALSAR has a 10m resolution. It allowed comprehensive monitoring of disasters by providing users with more detailed data than DAICHI/PALSAR. The observation frequency of ALOS-2 was improved by greatly expanding the observable range of the satellite up to about 3 times, througe an improvement in obserble areas (from 870km to 2,320km), as well as giving ALOS-2 a right-and-left looking function, not available on DAICHI/PALSAR.

ALOS-3 - Optical

The Advanced Optical Satellite is a successor of the optical mission of the Advanced Land Observation Satellite “DAICHI” (ALOS). The new satellite will achieve improved ground resolution (0.8 m) while observing a wide -swath (70 km) by a larger sensor with higher performance compared to DAICH, and continuously observe not only Japan but also global land areas to construct a system that can swiftly and timely acquire, process and distribute image data. Based on the accumulated data captured in pre- and post-disaster times, the satellite aims to become one of the imperative devices for disaster prevention and preparation activities of countries and municipal governments.

Observation data acquired by the satellite is also expected to be useful in various fields such as contributing to the maintenance and updates of precise geospatial information in Japan as well as developing countries, and research and applications on coastal and land environmental monitoring by its observation capabilities. The optical sensor onboard the Advanced Optical Satellite will improve its ground resolution by approx. three times from that of DAICHI (2.5 to 0.8 m at nadir) while maintaining a wide-swath of 70 km at nadir. Such a high-resolution sensor with a wide-swath is a unique characteristic of the sensor, which is achieved using maximize accumulated knowledge and manufacturing technology for a large optical system and a high resolution detector.

ALOS-4 - Radar

The Advanced Land Observing Satellite-4 (ALOS-4) is a satellite to observe the Earth's surface using its onboard phased array type L-band synthetic aperture radar (PALSAR-3). The L-band radar technology has continuously been developed in Japan. With further improved observation performance compared to the predecessor PALSAR-2 aboard the DAICHI-2 (ALOS-2), JAXA and its prime contractor, Mitsubishi Electric Corporation, are developing the satellite aiming at achieving both high resolution and a broader observation swath.

Unlike observations by an optical sensor, radar images can be acquired day and night as it does not require sunlight. Moreover, since radio waves can penetrate cloud, the images can be obtained regardless of weather condition. The ALOS-4 will leverage these merits for observing and monitoring disaster-hit areas, forests, and sea ice. In addition, it will also challenge new areas such as monitoring infrastructure displacement.

The ALOS-4 will be equipped with the Automatic Identification System for ships (AIS) receiver, as was DAICHI-2, so that the satellite will also monitor oceans by receiving AIS signals from vessels as well as by acquiring the PALSAR-3 images. The SPace based AIS Experiment (SPAISE3) is a high performance satellite AIS. Effective countermeasures against radio wave interference regions are taken for the SPAISE3 with multiple antennas and groundbased data processing; therefore, the detection success rate of a ship in the heavy marine traffic areas will be improved compared to DAICHI-2. SPAISE3 development is JAXA's ongoing project in cooperation with NEC Corporation.

If DAICHI-2 tried to cover all active volcanoes in Japan, it can observe one volcano just four times a year, hence more frequent observations would be performed only if a certain volcanic activity gets more active. ALOS-4 will increase the observation frequency to once every two weeks so that disaster prevention agencies can find abnormal changes such as unusual volcanic activity, land subsidence, or landslides at an early stage to timely warn people nearby. In addition, the observation swath will be drastically increased from 50 km to 200 km while keeping the high resolution. Therefore, we can observe a broader area at the same time when a large-scale disaster that damages wide areas occurs, such as a huge earthquake or multiple eruptions at the same time.