Shinichi Suzuki

SAR interferometry using ALOS-2 PALSAR-2 data for the Mw 7.8 Gorkha, Nepal earthquake

The Advanced Land Observing Satellite-2 (ALOS-2, “DAICHI-2”) has been observing Nepal with the Phased Array type L-band Synthetic Aperture Radar-2 (PALSAR-2) in response to an emergency request from Sentinel Asia related to the Mw 7.8 Gorkha earthquake on April 25, 2015. PALSAR-2 successfully detected not only avalanches and local crustal displacements but also continental-scale deformation. Especially, by the use of the ScanSAR mode, we are able to make interferograms that cover the entire displacement area of the earthquake. However, we did encounter some fundamental problems with the ScanSAR and incorrect settings of PALSAR-2 operation that have now been fixed. They include (1) burst overlap misalignment between two ScanSAR observations, which limits the number of pairs available and the quality of the interferogram, (2) non-crustal fringes which are derived from co-registration error and/or ionospheric effect and, (3) incorrect setting of the center frequency in the Stripmap beam F2-6. In this paper, we describe their problems and solutions. The number of interferometric pairs are limited by (1) and (3). The accuracy of the interferograms are limited by (2) and (3). The experimental results showed that current solutions for (2) and (3) work appropriately.

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 launch and early orbit operation result

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. ALOS-2 was launched on 24th May 2014, and is performing the initial functional verifications of onboard components and systems. This paper describes the initial operation results on orbit and evaluates the performance.

RFI detection and removal in Range-time Azimuth-frequency domain

In this paper, we report a radio frequency interference (RFI) detection method which is exclusively sensitive to the temporally pulsed wide-band signal. We use local autocorrelation in the range-time azimuth-frequency domain instead of typical range-frequency azimuth-time domain. Traditional RFI detectors assume that RFI have time-varying wide-band (TVWB) and / or time-stationary narrow-band (TSNB) features. The proposed method assumes that there is another type of RFI, namely, intermittently transmitted wide-band RFI. This kind of RFI superimposes on the SLC image however, its short pulse duration hinders us to detect it in range-frequency azimuth-time domain. Contrarily, in range-time azimuth-frequency domain, this kind of RFI can be detected easily. Here, we present a basic methodology and experimental results.

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.