This article has been accepted for inclusion in a future issue of this journal. Content is final as presented, with the exception of pagination. IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING 1 A Multifrequency Polarimetric SAR Processing Chain to Observe Oil Fields in the Gulf of Mexico Maurizio Migliaccio, Senior Member, IEEE, Ferdinando Nunziata, Student Member, IEEE, Antonio Montuori, Student Member, IEEE, Xiaofeng Li, Senior Member, IEEE, and William G. Pichel, Member, IEEE Abstract—Within the National Environmental Satellite, Data, and Information Service, National Oceanic and Atmospheric Ad- ministration, multiplatform synthetic aperture radar (SAR) im- agery is being used to aid posthurricane and postaccident response efforts in the Gulf of Mexico, such as in the case of the recent Deepwater Horizon oil spill. The main areas of interest related to such disasters are the following: 1) to identify oil pipeline leaks and other oil spills at sea and 2) to detect man-made metallic targets over the sea. Within the context of disaster monitoring and response, an innovative processing chain is proposed to observe oil fields (i.e., oil spills and man-made metallic targets) using both L- and C-band full-resolution and fully polarimetric SAR data. The processing chain consists of two steps. The first one, based on the standard deviation of the phase difference between the copolarized channels, allows oil monitoring. The second one, based on the different symmetry properties that characterize man- made metallic targets and natural distributed ones, allows man- made metallic target observation. Experiments, accomplished over single-look complex L-band Advanced Land Observing Satellite (ALOS) Phased Array type L-band Synthetic Aperture Radar (PALSAR) and C-band RADARSAT-2 fully polarimet- ric SAR data gathered in the Gulf of Mexico and related to the Deepwater Horizon accident, show the effectiveness of the proposed approach. Furthermore, the proposed approach, being able to process both L- and C-band fully polarimetric and full- resolution SAR measurements, can take full benefit of both the ALOS PALSAR and RADARSAT-2 missions, and therefore, it allows enhancing the revisit time and coverage which are very critical issues in oil field observation. Index Terms—Gulf of Mexico, man-made metallic target detec- tion, oil spill detection, synthetic aperture radar (SAR). Manuscript received October 29, 2010; revised February 8, 2011 and April 9, 2011; accepted May 19, 2011. This work was supported in part by the Italian Space Agency (ASI) under the contract I/066/090: “SAR Remote Sensing for Sea Oil Slick observation”. M. Migliaccio, F. Nunziata, and A. Montuori are with the Dipartimento per le Tecnologie, Universitá degli Studi di Napoli “Parthenope,” 80143 Napoli, Italy (e-mail: maurizio.migliaccio@uniparthenope.it; ferdinando.nunziata@ uniparthenope.it; antonio.montuori@uniparthenope.it). X. Li is with the I. M. Systems Group/National Environmental Satellite, Data, and Information Service, National Oceanic and Atmospheric Adminis- tration, Camp Springs, MD 20746 USA (e-mail: Xiaofeng.Li@noaa.gov). W. G. Pichel is with the Center for Satellite Applications and Research, National Environmental Satellite, Data, and Information Service, National Oceanic and Atmospheric Administration, Camp Springs, MD 20746 USA (e-mail: William.G.Pichel@noaa.gov). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TGRS.2011.2158828 I. I NTRODUCTION T HE GULF OF Mexico is one of the largest basins in the world, located south of the U.S. and north of Mexico. It serves an important role in the worldwide economy due to its oil fields that are at the core of the petrochemical industry of the U.S. In fact, there are thousands of oil and gas rigs a few miles away from the coast running from Texas to Louisiana and the state of Mississippi. A recent estimate indicates that there are approximately, in June 2010, 3445 oil and gas structures in the Gulf of Mexico, producing, in October 2010, 29% of the oil and 13% of the natural gas produced in the U.S. [1]. However, these oil rigs pose an important environmental risk in the case of disasters and accidents, such as the recent massive Deepwater Horizon oil spill, which is considered the largest offshore spill in U.S. history. In addition to such disasters/accidents, the Gulf of Mexico is prone to hurricanes. During such events, man-made metallic infrastructures, such as oil rigs, can be wrecked or destroyed, accompanied by release of oil at sea [2]. Therefore, both oil-at- sea monitoring and man-made metallic target observation are very important issues. They represent two complex activities that cannot be solved just by means of conventional observa- tion techniques, i.e., coast guard ships and aerial observation. Accordingly, coastal managers are continuously interested in knowing the real-time positions of all the oil rigs, particularly after the passage of hurricanes. The main reason for such an observation is to identify possible oil pipeline leaks on the sea surface and to detect changes in man-made metallic targets, thus providing firsthand information on potential oil drilling infrastructure damage. Within such a framework, synthetic aperture radar (SAR) plays a fundamental role since it allows overcoming the constraints of in situ techniques and ensures improved spatial/temporal coverage. SAR is an active coherent band-limited microwave high-resolution sensor that can make daytime and nighttime measurements almost independent of at- mospheric conditions. However, observing oil slicks and man- made metallic targets at sea by means of SAR is not an easy task due to both technical, e.g., false alarms, speckle, etc., and technological, e.g., spatial resolution, spatial and/or temporal coverage, etc. In this paper, for the first time, a polarimetric approach that embodies both oil slick and man-made metallic target observations is proposed. In order to properly frame this paper, the relevant state of the art is hereafter briefly summa- rized. Since the states of the art of SAR oil slick observation and SAR man-made metallic target detection are disjoint, they are described separately. 0196-2892/$26.00 © 2011 IEEE