Yukihiro Kankaku

ALOS-2 mission and development status

JAXA is developing the Advanced Land Observing Satellite-2 (ALOS-2) carrying the state of the art L-band SAR named PALSAR-2. ALOS-2 mission is the follow-on of ALOS “Daichi” mission and PALSAR-2 succeeds to PALSAR onboard ALOS. PALSAR contributed to domestic and international disaster management activities by its interferometric application (InSAR). Compared to the PALSAR, higher spatial resolution, better NESZ (Noise Equivalent Sigma Zero) and better S/A (Signal to Ambiguity ratio) are required for PALSAR-2. In order to meet these requirements, JAXA introduced several improvements such as maximum bandwidth observation for PALSAR-2, spotlight mode with Active Phased Array Antenna, high power efficiency device, chirp modulation technique and dual receiving antenna system. In addition, very accurate orbit control and short repeat-pass orbit (14 days) will give higher coherence of interferometry.

PALSAR-2 launch and early orbit status

The Advanced Land Observing Satellite-2 (ALOS-2) is the RADAR satellite which is carrying the state-of-the-art L-band Synthetic Aperture Radar (SAR) called PALSAR-2 (Phased Array type L-band SAR-2) which succeeds to the PALSAR mounted on ALOS “Daichi”. PALSAR had contributed to various applications such as disaster, deformation, deforestation, agriculture and natural resource monitoring by providing enormous observation data from 2006 to 2011. Therefore, ALOS-2 is expected to continue the ALOS PALSAR mission and its contributions. ALOS-2 was successfully launched by H-IIA rocket from Tanegashima Space Center at 24th May 2014. This paper shows the initial status of PALSAR-2 after launch.

Hardware performance of L-band SAR system onboard ALOS-2

Advanced Land Observation Satellite-2 (ALOS-2) is a space borne Synthetic Aperture Radar (SAR) system, which is the follow-on L-SAR satellite mission of ALOS. Compared to the previous mission ALOS/PALSAR, the new L-band SAR system is capable of achieving both high resolution (down to 1m) and wide swath (up to 500km), with an improved image quality. The hardware (H/W) of ALOS-2, including L-band SAR sensor, is developed by Mitsubishi Electric Corporation under the contract of Japan Aerospace and Exploration Agency (JAXA). This paper describes the H/W design and performance of the ALOS-2 SAR sensor with a focus on the engineering model (EM) test performance.

Overview of Japan's Advanced Land Observing Satellite-2 mission

The post-ALOS program has been defined in the basic plan for Japans space policy which was established by the Strategic Headquarters for Space Policy on June 2nd, 2009. It emphasizes the continuity of the ALOS mission not only disaster monitoring but also land infrastructure management, earth environment and resource monitoring and so on. JAXA had completed the System Definition Review of the ALOS-2 satellite and ground system in February, 2009 and started phase B design of the new L-band SAR, satellite and ground system with the target launch in 2013.This paper introduces the mission and major specification of ALOS-2 satellite and L-band SAR.

ALOS-2 acquisition strategy

The Advanced Land Observing Satellite-2 (ALOS-2) carries the state-of-the-art L-band Synthetic Aperture Radar (SAR) called PALSAR-2 which succeed to the ALOS / PALSAR. Since more acquisition modes of PALSAR-2 than those of PALSAR may trigger more conflicts among user requests, systematic acquisition strategy is very important to achieve the mission requirements. For example, trade-off studies have been made for INSAR basemap data acquisition through discussion with user groups, and an optimum scenario was proposed to fulfill both requirements for quick response and time-series data acquisition under a same condition (incidence angle, descending/ascending, left/right look). As the ALOS data resulted in a comprehensive and homogeneous global archive, consistent data archives will be requested for ALOS-2 as well. This paper describes a draft acquisition strategy for PALSAR-2.

PALSAR-2 initial mission check

PALSAR-2 (Phased Array type L-band Synthetic Aperture Radar-2) is a spaceborne L-band SAR (Synthetic Aperture Radar) system installed on Japanese Advanced Land Observing Satellite-2 (ALOS-2). PALSAR-2 is expected to provide valuable data for global monitoring and disaster monitoring. To meet the variety of demands, PALSAR-2 provides various operational modes. This paper describes the overview of the calibration plan of PALSAR-2. Since PALSAR-2 have more than 1,000 operational modes, effective and efficient procedure is crucial. The process is divided in three different phases; pre-launch calibration, check-out phase (C/O phase) after the launch, and image calibration phase. The overview of each phase is described.

Overview of ALOS-2 and ALOS-3

ALOS-2 and ALOS-3 will succeed to radar and optical mission of Advanced Land Observing Satellite “Daichi” which had contributed to cartography, regional observation, disaster monitoring, and resources surveys for more than 5 years until its termination of operation in May 2011. ALOS-2 carries the state-of-the-art L-band Synthetic Aperture Radar (SAR) called PALSAR-2 which succeeds to the ALOS/PALSAR with enhanced performance in both high resolution (1m * 3m at finest in the Spotlight mode) and wide swath (up to 490km in the ScanSAR wide mode). Wider bandwidth and shorter revisit time will give better conference for INSAR data analysis such as crustal deformation and deforestation. The Proto Flight Model of ALOS-2 including PALSAR-2 is under integration and testing at JAXA’s Tsukuba Space Center. ALOS-3 carries the optical sensor called PRISM-2 which succeeds to the ALOS/PRISM mission with enhanced performance in high resolution (0.8 m), wide swath (50 km) and high geo-location accuracy. PRISM-2 will acquire stereo pair images with two telescopes for stereo mapping and precise Digital Surface Models. It is also considered to carry Hyper-spectral Imager Suite (HISUI), which is developed by the Ministry of Economy, Trade and Industry (METI) of Japan. JAXA has conducted the phase-A study on ALOS-3 spacecraft and mission instruments, with prototype testing of key components. This paper describes an overview of ALOS-2 and ALOS-3.

System design of wide swath, high resolution, full polarimietoric L-band SAR onboard ALOS-2

This paper describes SAR system design of the Advanced Land Observing Satellite-2 (ALOS-2), which is a next-generation Japanese L-band SAR satellite. Since one of an important mission of ALOS-2 is a global monitoring using its unique frequency of L-band, a capability of wider coverage is required. On the contrary, in the point of disaster monitoring especially for urban area, relatively higher spatial resolution is essential. To comply with such a contradictive requirement of wide swath and high resolution, ALOS-2 utilizes a dual-receive channel (DRC) technique, and achieved a coverage area of up to 50km with a spatial resolution of down to 3m. In the paper, the H/W design of ALOS-2 DRC mode is explained. For a wider coverage of polarimetric observation, ALOS-2 installs the fully redundant and “quad-receive channel” system to full-polarimetric mode, achieving a maximum coverage of 50km at 6m resolution. As an experimental mode, new polarimetric mode called “compact polarimetry” is installed for a wide coverage of polarimetric observation.

ALOS-2 current status and operation plan

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 will have 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 INSAR data analysis such as crustal deformation and deforestation. The Proto Flight Test (PFT) of ALOS-2 has been conducted since June 2012. In parallel, the PFT of PALSAR-2 has been conducted since March 2012. As of August 2013, ALOS-2 system has completed the interface test with ground system and is preparing for the Vibration test, Acoustic test and Electromagnetic Compatibility test. After completing these tests, ALOS-2 will be transported to JAXA Tanegashima Space Center for launch. The initial commissioning phase of ALOS-2 is planned for six months which are comprised of LEOP (Launch and Early Orbit Phase) and initial Cal/Val phase. During the LEOP, all components will be checked with direct downlink via Xband and with data relay communication via JAXA’s DRTS (Data Relay Test Satellite). During the initial Cal/Val phase, the PALSAR-2 data will be verified and calibrated by using Corner Reflectors and Geometric Calibrator at ground. The data acquisition during the commissioning phase will be consistent with the systematic acquisition strategy prepared for the routine operation. This paper describes the current status and operation plan of ALOS-2.

Development status of PALSAR-2 onboard 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. PALSAR-2 has a Spotlight mode (1 to 3 m), a Stripmap mode (3 to 10 m) and a ScanSAR mode, whilst PALSAR onboard ALOS had 10 m spatial resolution at best. The new technologies, such as maximum bandwidth allocation for L-band SAR, the spotlight mode with Active Phased Array Antenna, high power efficiency device of GaN and chirp modulation technique, have been verified by testing its Engineering Model (EM). The critical design of ALOS-2 including PALSAR-2 was completed in June 2011. This paper describes current development status of ALOS-2 and brief results of EM.