Foreword to the Special Issue on Calibration and ... - IEEE Xplore

IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING, VOL. 47, NO. 12, DECEMBER 2009

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Foreword to the Special Issue on Calibration and Validation of ALOS Sensors (PALSAR, AVNIR-2, and PRISM) and Their Use for Bio- and Geophysical Parameter Retrievals

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HE ADVANCED Land Observing Satellite (ALOS) (“Daichi” in japanese) was launched on January 24, 2006. ALOS carries three remote sensing high-resolution sensors: the Phased Array L-band Synthetic Aperture Radar (PALSAR), the Advanced Visible and Near Infrared Radiometer (AVNIR-2), and the Panchromatic Remote Sensing Instrument for Stereo Mapping (PRISM). To fully utilize these sensor data, the Japan Aerospace Exploration Agency initiated the calibration of the three ALOS sensors within the worldwide collaborative frame on collecting the ground truth data, validating the sensor parameters with reference to the original specification, and assessing the calibration methodologies. By now, these three state-of-the-art sensors, whose calibration/validations have been completed, have provided high-quality and accurate Earth images that permit an enhanced and accurate retrieval of target geophysical parameters. With its three high-resolution optical and synthetic aperture radar (SAR) sensors, ALOS is providing the required information for the generation of accurate digital elevation models, regional remote sensing observations for sustainable development, disaster mitigation and monitoring, exploration of natural resources, climate change impact monitoring, and a wide range of operational utilization, in the near future. The ALOS radar sensor PALSAR is an L-band SAR, with a high-resolution and high-quality imaging capability allowing an average ground resolution of 10 m, a high transmission power of 2 kW, and the ability to change the incidence angle (from 7.7◦ to 60◦ ). PALSAR has five observation modes: 1) fine-beam single mode, with a slant range resolution of 5 m, a 70-km imaging swath, and single polarization; 2) finebeam dual mode, with a medium-range resolution of 10 m, a 70-km swath, and two orthogonal polarizations for reception; 3) polarimetry mode, with a 35-km swath, a 10-m slant range resolution, and full polarizations for transmission and reception; 4) ScanSAR mode, with a 100-m resolution, a 350-km swath, and single polarization; and 5) direct single downlink mode, with a 10-m resolution, a 70-km swath, and single polarization. The PALSAR has been radiometrically and geometrically calibrated using corner reflectors deployed worldwide. The radar wavelength is 23.6 cm, almost the same as the one used by GPS. Thus, the SAR can observe the Earth’s surface

Digital Object Identifier 10.1109/TGRS.2009.2036389

by penetrating the above-ground biomass of tree trunks and canopies, independent of the weather and day–night conditions. Thus, when used for interferometric SAR analysis, PALSAR provides quantitative deformation and height maps for even highly vegetated land areas. However, when a frequency that is lower than or equal to L-band is used, the ionosphere between the Earth and the satellite rotates the polarization vector of the radar signal. This is well known as the Faraday rotation that associates with the Earth’s magnetic field and the ionosphere’s refractive index, affecting the signal propagation speed. Thus, another application of the PALSAR L-band SAR data could be to estimate properties of the ionosphere. PRISM is a high-resolution imaging system with a bandpass of 0.52–0.77-µm wavelength. PRISM incorporates three telescopes that provide images at nadir and stereo viewing in forward and backward directions. The nadir ground resolution is 2.5 m. Knowing the exact location of the sensor and the sensor’s viewing direction, the triangular expression for the height and the image shift between the two telescopes on the target plane gives the height information at the spacing of 2.5 m. PRISM covers a 35-km imaging swath and provides highly accurate digital elevation models in cloud-free conditions. AVNIR-2 has a ground resolution of 10 m at the nadir viewing. The sensor provides images in four wavelength channels ranging from 0.42 to 0.89 mm. The wide range of the incidence within 44◦ provides the coverage of 1500 km on the ground. The 70-km imaging swath can allow the quick coverage of the target, and on average, 2.5 days is the repeat period of target observations. This is very useful for disaster mitigation and observation. The objective of this Special Issue dedicated to ALOS is to select outstanding papers that describe the calibration and validation of the ALOS sensors (PALSAR, AVNIR-2, and PRISM) and their use for bio- and geophysical parameter retrievals. We obtained an excellent response from the call for papers for this Special Issue, with a total of 30 papers submitted. As a result of a careful review process, 17 papers have been accepted for publication. The first papers of the issue are dedicated to the calibration of PALSAR for the retrieval of pure polarization measurements at low and significant Faraday rotation conditions. The following six papers provide an excellent demonstration of PALSAR potential for various key applications: agriculture crop classification, forest monitoring and biomass measurement, surface roughness retrieval,

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and oil slick observation. The last five papers are dedicated to the optical sensor (AVNIR-2 and PRISM) calibration and applications. The guest editors would like to thank Prof. C. Ruf, the TGARS Editor, for his help with the Special Issue. We would also like to thank Prof. Wooil M. Moon, Dr. Maurice Borgeaud, and the reviewers for their excellent evaluation of the papers. In many cases, the papers were significantly improved by the reviewers’ comments and suggestions.

M ASANOBU S HIMADA, Guest Editor Earth Observation Research Center Japan Aerospace Exploration Agency Ibaraki 305-8505, Japan R IDHA T OUZI, Guest Editor Canada Centre for Remote Sensing Natural Resources Canada Ottawa, ON K1A 0Y7, Canada TAKE TADONO, Guest Editor Japan Aerospace Exploration Agency Earth Observation Research Center Ibaraki 305-8505, Japan JAMES A. S MITH, Guest Editor NASA Goddard Space Flight Center Greenbelt, MD 20771 USA

Masanobu Shimada (M’97–SM’04) received the B.S. and M.S. degrees in aeronautical engineering from Kyoto University, Kyoto, Japan, in 1977 and 1979, and the Ph.D. degree in electrical engineering from the University of Tokyo, Tokyo, Japan, in 1999. In 1979, he joined the National Space Development Agency of Japan [NASDA, currently known as the Japan Aerospace Exploration Agency (JAXA)], Tsukuba, Japan, where he designed a NASDA scatterometer. From 1985 to 1995, he was with the Earth Observation Center, where he developed data-processing subsystems for optical and SAR data (MOS-1, SPOT, and Japanese Earth Resources Satellite). In 1990, he was a Visiting Scientist with the Jet Propulsion Laboratory. Since 1995, he has been assigned duties at the Earth Observation Research Center, JAXA, where he was an Advanced Land Observing Satellite (ALOS) Science Manager (ALOS CAL/VAL, rainforest mapping projects, and SAR interferometry projects) and is currently an Associate Principal Researcher.

Ridha Touzi (M’93) received the Ingenieur degree from l’Ecole Nationale de l’Aviation Civile, Toulouse, France, in 1983, the DEA and M.S. degrees from l’Ecole Nationale Supérieure de l’Aéronautique et de l’Espace, Toulouse, in 1984, and the Ph.D. degree and le diplôme de l’Habilitation à diriger des recherches from l’Université Paul Sabatier, Toulouse, in 1988 and 1996, respectively. From 1988 to 1990, he was a Research Scientist with the Centre d’Etude Spatiale des Rayonnements. From 1990 to 1992, he was a Canadian Government Laboratory Visiting Fellow with the Canada Centre for Remote Sensing (CCRS), Ottawa. From 1992 to 1994, he was a Professor with the Royal Military College of Saint-Jean, Québec, Canada. Since 1994, he has been a Research Scientist with CCRS. His research interests include many aspects of synthetic aperture radar (SAR) image processing, polarimetry, interferometry, and airborne and spaceborne SAR calibration. Dr. Touzi has been a member of the JAXA ALOS calibration–validation team since 2006. He is also a member of the RADARSAT-2 Calibration and Image Quality Group and Radar Constellation Mission Image Quality Group led by the Canadian Space Agency. He was the recipient of the 1999 Geoscience and Remote Sensing Transactions Prize Paper Award for the study on the “coherence estimation for SAR imagery.” He was also the recipient of the Natural Resources Canada 2003 award for his significant contribution on the field of polarimetry in Canada and on Canada’s preparation of RADARSAT-2.


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Takeo Tadono (M’04) received the B.E., M.E., and Ph.D. degrees in civil engineering from the Nagaoka University of Technology, Nagaoka, Japan, in 1993, 1995, and 1998, respectively. He is currently an Associate Senior Researcher with the Earth Observation Research Center, Japan Aerospace Exploration Agency, Tsukuba, Japan, where he is in charge of calibrating and validating optical instruments on the Advanced Land Observing Satellite (ALOS). His research interests are calibration of high-resolution optical instruments and development of inversion algorithms for retrieving geophysical parameters from remote sensing data, particularly soil moisture and snow parameters using microwaves. Dr. Tadono was the Secretary of Geoscience and Remote Sensing Society of IEEE Japan Chapter in 2004.

James A. Smith (F’96) is a Senior Scientist and Goddard Senior Fellow in the Hydrospheric and Biospheric Sciences Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD. Currently, he is using satellite-based remote sensing and individually based mechanistic models to simulate bird migration patterns at continental scales in response to changes in the environment. Dr. Smith has previously served as an Associate Editor for Visible and Infrared Remote Sensing and as the Editor-in-Chief of the IEEE T RANSACTIONS ON G EOSCIENCES AND R EMOTE S ENSING. He is the recipient of the NASA Exceptional Service Medal in recognition of his contributions to the establishment and development of the land processes and biospheric physics program. He was elected a Fellow of the IEEE for development of optical and thermal canopy signature models, basic terrain feature measurements, and application to remote sensing. Additionally, a Fellow of the AAAS and SPIE, he presently serves on the Environmental Security panel for the NATO Science for Peace and Security Programme.