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 ALOS-2, JAXA and its prime contractor, Mitsubishi Electric Corporation, developed ALOS-4 aiming at achieving both high resolution and a broader observation swath. 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 warn people nearby. In addition, the observation swath will be drastically increased from 50km to 200km 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. ALOS-4 was launched by the 3rd H3 launch vehicle at JAXA’s Tanagashima Space Center, Japan. This paper describes the ALOS-4’s initial operation results and its performance.
The Advanced Land Observing Satellite-4 (ALOS-4) is the following mission of the Advanced Land Observing Satellite-2(ALOS-2). ALOS-4 carries two instruments, one is Phased Array-type L-band Synthetic Aperture Radar-3 (PALSAR-3) and the other is SPace based AIS for ships Experiment (SPAISE3). PALSAR-3 is the successor of PALSAR-2 aboard ALOS-2 and SPAISE3 is the successor of SPAISE2 aboard ALOS-2. Proto Flight Tests (PFT) for the ALOS-4 satellite system and the total end-to-end test including the ALOS-4 satellite system and ground segments were already completed. The operation preparations including operation training, calibration/validation preparation and coordination with users are on-going.
This paper describes the current status of PALSAR-3, L-band Synthetic Aperture Radar (SAR) boarded on Advanced Land Observing Satellite-4 (ALOS-4). ALOS-4 is the following mission of the ALOS-2 and the fourth generation of Japanese L-band SAR missions. PALSAR-3 has three observation modes same as PALSAR-2 boarded on ALOS-2. The same orbit and observation geometry as PALSAR-2 are selected to enable interferometric SAR (INSAR) time series analysis over 10 years using both of PALSAR-2 and PALSAR-3 data. PALSAR-3 will have the Basic Observation Scenario (BOS), same as PALSAR-2.
The Advanced Land Observing Satellite-2 (ALOS-2) carries the phased array type Synthetic Aperture Rader (SAR) with the L-band frequency named PALSAR-2. ALOS-2 provides necessary data for disaster management, land and infrastructures management, resource management and so on. For disaster management by satellite based SAR, high resolution and wide swath width observation are needed. The Pulse Repetition Frequency (PRF) must be higher to improve azimuth resolution with less ambiguity caused by aliasing, but lower PRF is necessary to realize wider swath width. From this reason, high resolution and wide swath width are conflicting requirements for SAR. We have realized the requirements by adopting the multi-beam technology. PALSAR-2 has one transmitter and two receivers (dual beam system). This makes possible to reduce PRF and PALSAR-2 enables to receive the back scatterings, which are received in twice in the single beam receiver, at the same time. Therefore PALSAR-2 can realize high resolution and wide swath width capabilities by mean of the dual beam system. Improving resolution and swath width leads to increasing the data volume. Large amount of data need longer time to send the data to ground stations. From this reason the high speed data transmitting system with multi-mode X-band modulator has been developed. The modulator works with 800Mbps in 16QAM mode. This paper presents the initial on-orbit checkout result of ALOS-2.
The Advanced Land Observing Satellite-2 (ALOS-2) carries the state-of-the-art L-band Synthetic Aperture Radar (SAR) called PALSAR-2 which succeeds to the ALOS / PALSAR. PALSAR-2 has an enhanced performance in both high resolution and wide swath compared to PALSAR. It will allow comprehensive monitoring of disasters. Wider bandwidth and shorter revisit time will give better conference for interferometry SAR (INSAR) data analysis such as crustal deformation and deforestation. ALOS-2 was launched on 24th May 2014, and has been completed the initial functional verifications of onboard components and systems. This paper describes the initial operation and checkout results including the comparison with the previous SAR satellite image and the disaster monitoring. Some key features of orbit control and determination to improve the coherency of the repeat-pass INSAR observation are evaluated.
The Advanced Land Observing Satellite-2 (ALOS-2) is a follow-on mission from ALOS "Daichi". The state-of-the-art
L-band Synthetic Aperture Radar (SAR) aboard ALOS-2 will, in response to society's needs, have enhanced
performance compared to ALOS/PALSAR. ALOS-2 will have a spotlight mode (1 and 3 m) and a high-resolution mode
(3 to 10 m), while PALSAR has 10m resolution. The Preliminary Design was completed in March, 2010. Phase C/D has
been started and the Engineering Models are currently under development. This paper describes the current development
status of ALOS-2.
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