ALOS PALSAR

ALOS PALSAR
Name	ALOS PALSAR
Mission type	Remote sensing
Operator	Japan Aerospace Exploration Agency
Launch date	2006-01-24
Launch vehicle	H-IIA
Launch site	Tanegashima Space Center
Orbit	Sun-synchronous
Instruments	Phased Array type L-band Synthetic Aperture Radar

ALOS PALSAR ALOS PALSAR was an L-band radar instrument flown aboard a Japanese Earth observation satellite, designed to provide high-resolution interferometric and polarimetric imagery for land cover, forestry, disaster monitoring, and geodesy. It operated in tandem with international programs and national agencies to support operational mapping, scientific research, and emergency response, producing datasets used by numerous institutions and researchers worldwide.

Overview

PALSAR was developed by the Japan Aerospace Exploration Agency in collaboration with industry partners including NEC Corporation and Mitsubishi Electric Corporation, launched on an H-IIA from Tanegashima Space Center, and operated in a Sun-synchronous orbit to provide repeat-pass capability. The instrument complemented sensors such as Landsat 7, TerraSAR-X, Sentinel-1, RADARSAT-2, and Envisat ASAR, enabling cross-comparison with missions from NASA, European Space Agency, Canadian Space Agency, and Indian Space Research Organisation. Users included research centers like JAXA, USGS, NASA JPL, NIES, NICT, and universities such as University of Tokyo, Tohoku University, Massachusetts Institute of Technology, and Stanford University.

Instrumentation and Specifications

PALSAR was a Phased Array type L-band Synthetic Aperture Radar designed to operate at ~1.27 GHz, with polarization modes and multiple beam modes for Stripmap and ScanSAR acquisitions. Its technical specifications were specified by JAXA engineers and validated by vendors including NEC, Mitsubishi Electric, and laboratories such as National Institute of Information and Communications Technology and Electrotechnical Laboratory. The instrument supported single, dual, and full polarization, with spatial resolutions comparable to systems on TerraSAR-X, RADARSAT-2, and Sentinel-1A, and swath options useful for mapping at scales used by agencies like USGS and research groups at University of Massachusetts Amherst and University of California, Berkeley.

Mission Timeline and Operations

PALSAR was launched aboard ALOS on 24 January 2006 and entered routine operations providing datasets to international consortia, national agencies, and scientific projects until operational issues affected the platform. The mission timeline intersected with events and programs such as the 2008 Sichuan earthquake, 2011 Tōhoku earthquake and tsunami, and international initiatives led by GEO, CEOS, and Group on Earth Observations projects. Ground segment operations integrated facilities at Tanegashima Space Center, JAXA data centers, and partner nodes at USGS Earth Resources Observation and Science (EROS) Center, ESA, and university processing centers.

Data Products and Processing

PALSAR produced levelled data products analogous to products from Sentinel-1, RADARSAT-2, and Envisat, including Single Look Complex, ortho-rectified terrain-corrected imagery, and interferometric stacks used in coherence and deformation studies by teams at Caltech, Columbia University, Imperial College London, and ETH Zurich. Processing chains used software libraries and toolkits from ASF DAAC, GEO, GMTSAR, ISCE, and commercial processors developed by MDA Corporation and academic implementations from INPE. Data distribution policies enabled access through archives similar to those operated by USGS, ESA, and JAXA, with multiprocessing workflows leveraging computing facilities such as NERSC, CASC, and university clusters.

Applications and Scientific Contributions

PALSAR datasets supported forestry biomass mapping by researchers at INPE, NASA Goddard, CSIRO, and CIFOR, wetland and peatland studies involving teams from Wetlands International and International Union for Conservation of Nature, and land deformation measurements by groups at CALTECH JPL, University of Tokyo, and GFZ German Research Centre for Geosciences. Disaster applications included flood mapping for the 2007 Niigata Chuetsu-oki earthquake response, landslide analysis alongside USGS and British Geological Survey, and tsunami inundation mapping for the 2011 Tōhoku earthquake and tsunami. The sensor contributed to carbon cycle studies involving IPCC assessments and to agricultural monitoring used by institutions such as FAO and national ministries across Indonesia, Brazil, Australia, and Canada.

Calibration, Validation, and Limitations

Calibration and validation campaigns involved international test sites and agencies including CEOS, GEO, JAXA, NASA JPL, DLR, CSA, NRCan, and universities such as University of Calgary and UNB. Limitations included sensitivity to ionospheric disturbances documented by studies from NICT, decorrelation effects in high-relief areas studied by USGS and GFZ, and operational constraints after platform anomalies which curtailed some polarimetric operations studied by ISRO and regional partners. Validation used field measurements from institutes like CIFOR and INIA and airborne campaigns coordinated with NASA Airborne Science Program.

International Collaboration and Data Policy

PALSAR data sharing involved agreements between JAXA, NASA, ESA, Canadian Space Agency, Australian Department of the Environment, and national research institutions, supporting data access for research groups at University of Oxford, Peking University, Kyoto University, Seoul National University, and University of São Paulo. Collaborative projects included joint efforts under CEOS, GEO, APEC, and bilateral memoranda with agencies such as USGS and NRCan, enabling multi-mission synergistic research with Landsat, Sentinel-1, TerraSAR-X, and ICESat datasets.

Category:Earth observation satellites Category:JAXA spacecraft Category:Synthetic aperture radar