Monitoring Marine Ecosystems with Synthetic Aperture Radar DON ATWOOD, Ph.D. Alaska Satellite Facility
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Monitoring Marine Ecosystems with Synthetic Aperture Radar DON ATWOOD, Ph.D. Naval Postgraduate Workshop – 9Facility August AlaskaSchool Satellite Don Atwood 1 Alaska Satellite Facility (ASF) • Operated by the Geophysical Institute (University of Alaska Fairbanks) • NASA Archive for Seasat, ERS-1,2, JERS-1, AirSAR, RADARSAT-1, and ALOS PALSAR • ASF operates on a 24x7 schedule • 50,000 image products per year • U.S. Order Desk for 3 SAR Satellites: •RADARSAT-1, ERS-2, and ALOS • Operational SAR support for NOAA and National Ice Center (NIC) Naval Postgraduate School Workshop – 9 August Don Atwood 2 Global Mask Coverage for R-1 R-1 data available from: • Fairbanks, Alaska (ASF) • Prince Albert (PASS) • Gattineau (GSS) • McMurdo, Antarctica (MCM) • Tromso, Norway (TROM) • West Freugh, Scotland (Qinetiq) • Bejing, China (RSGS) • Miami, Florida (CSTARS) • Cordoba, Argentina (CONAE) • Istanbul, Turkey(ITU) Naval Postgraduate School Workshop – 9 August Don Atwood 3 ASF Receiving Ground Station ASF Receiving Mask Naval Postgraduate School Workshop – 9 August Don Atwood 4 SAR Coverage of the Bering Sea Three-Day, RADARSAT-1 Coverage • Ascending and Descending Swaths • ScanSAR Wide B (460 km swaths) Naval Postgraduate School Workshop – 9 August Don Atwood 5 Past SAR Satellites Seasat • Launched 1978 by JPL • 23.5 cm (L-Band) • HH Polarization • 100 km swath • 25 m resolution • 24 day Repeat Cycle Naval Postgraduate School Workshop – 9 August ERS-1 • Launched 1991 by ESA • 5.66 cm (C-Band) • VV Polarization • 100 km swath • 30 m resolution • 35 day Repeat Cycle Don Atwood JERS-1 • Launched 1992 by NASDA • 23.5 cm (L-Band) • HH Polarization • 75 km Swath • 30 m resolution • 44 day Repeat Cycle 6 Active SAR Satellites RADARSAT-1 • Launched 1995 by CSA • 5.66 cm (C-Band) • HH Polarization ERS-2 • 50 – 460 km swath • Launched 1995 by ESA • 10 -100m resolution • 5.66 cm (C-Band) • 24 day Repeat Cycle • VV Polarization • 100km swath • 30 m resolution • 35 day Repeat Cycle Naval Postgraduate School Workshop – 9 August Don Atwood ALOS PALSAR • Launched 2006 by JAXA • 23.6cm (L-Band) • Single, Dual, Full Polarization • 70-350km Swath • 12.5 -100m resolution • 46 day Repeat Cycle 7 Emergency Response Selendang Ayu Incident NRT SAR provided to U.S. Coast Guard Naval Postgraduate School Workshop – 9 August Don Atwood 8 NRT Support Walrus Tracking U.S. Fish and Wildlife Service USGS Alaska Science Center Naval Postgraduate School Workshop – 9 August Don Atwood 9 NRT Support Coastal Environment U.S. Fish and Wildlife Service USGS Alaska Science Center Naval Postgraduate School Workshop – 9 August Don Atwood 10 But for other applications, we need some Physics……. © CSA 2006 Strait of Gibraltar Naval Postgraduate School Workshop – 9 August Don Atwood 11 Microwave Interactions What does SAR see? Hurricane Ivan Naval Postgraduate School Workshop – 9 August Don Atwood 12 Microwave Interactions What does SAR see? • surface roughness of the water Fortunately, wind, atmospheric, and oceanographic phenomena modulate the surface roughness Hurricane Ivan Naval Postgraduate School Workshop – 9 August Don Atwood 13 Microwave Interactions Capillary Waves Naval Postgraduate School Workshop – 9 August Smooth Water Don Atwood Ships 14 Microwave Interactions Bragg scattering from Gravity-capillary Waves Gravity-capillary Waves • Produced by Wind • Order of 1 cm wavelength • Modulated by Marine Phenomena Close-up photo of Capillary Waves Naval Postgraduate School Workshop – 9 August Don Atwood 15 SAR Fundamentals Dependence on Incidence Angle Smooth Surfaces: Angle of incidence equals the angle of reflection (specular reflection). No backscattered microwaves. Water is dark. Real Surfaces: Backscatter diminishes with increasing Incidence Angle Naval Postgraduate School Workshop – 9 August Don Atwood 16 SAR Fundamentals Polarization Horizontal Transmit Horizontal Receive HH HV VV VH Vertical Transmit Horizontal Receive Vertical Transmit Vertical Receive Naval Postgraduate School Workshop – 9 August Horizontal Transmit Vertical Receive Don Atwood 17 Atmospheric Effects • SAR “sees” the surface manifestation of atmospheric phenomena • Wind increases surface roughness, surface roughness increases radar backscatter • Only requirement is that atmosphere effect extend to ocean surface Naval Postgraduate School Workshop – 9 August Don Atwood 18 Atmospheric Effects Atmospheric Fronts Vortex Streets Bering Sea Naval Postgraduate School Workshop – 9 August Aleutians Don Atwood 19 Atmospheric Effects Cyclonic Patterns Convection Cells Gulf of Alaska Bering Sea Naval Postgraduate School Workshop – 9 August Don Atwood 20 Wind Speed Retrieval • Semi-empirical formula used to yield ocean surface wind fields • Sub-km resolution with SAR, in open ocean and coastal environments • Scatterometers yield 25 km resolution, limited to open ocean Wind retrieval: • Valid for wind speeds of 3 - 35 m/s • Accuracy (from buoy validation) is +/-1.6 m/s • Accuracy limited by wind direction errors Naval Postgraduate School Workshop – 9 August Don Atwood 21 Wind Retrieval Wind Rows Wind Shadows Bering Sea Naval Postgraduate School Workshop – 9 August Cook Inlet Don Atwood 22 Wind Speed Retrieval • Quasi-Operational program developed under NOAA/NESDIS-sponsored Alaska SAR Demonstration (AKDEMO) • Retrieval software developed by JHU Applied Physics Laboratory Naval Postgraduate School Workshop – 9 August Don Atwood 23 Wind Speed Retrieval Demonstration of retrieval from ALOS L-band data Naval Postgraduate School Workshop – 9 August Don Atwood 24 Wind Speed Retrieval ASF web page for wind products Google .kmz files now available http://wind.asf.alaska.edu Naval Postgraduate School Workshop – 9 August Don Atwood 25 Oceanographic Features • Oceanographic features modulate the surface capillary waves, via: • stretching of waves • tilt modulation • hydrodynamic effects • velocity bunching Naval Postgraduate School Workshop – 9 August Don Atwood 26 Oceanographic Features Long Surface Waves Dipole Eddies San Francisco Bay Naval Postgraduate School Workshop – 9 August St. Matthew Is. Don Atwood 27 Oceanographic Features Sand Bars and Shoal Waters National Ocean Service (NOS) Office of Coast Survey - US Bathymetric & Fishing Maps Kuskokwim Bay Naval Postgraduate School Workshop – 9 August Don Atwood 28 Oceanographic Features SAR & Optical Data Fusion U.S. Fish and Wildlife Service USGS Alaska Science Center Naval Postgraduate School Workshop – 9 August Don Atwood 29 Oceanographic Features GhostNet – Marine Debris Detection in the North Pacific and Gulf of Alaska Subtropical convergence fronts can be located using SAR, satellite SST, and chlorophyll imagery Naval Postgraduate School Workshop – 9 August Don Atwood 30 Slick Detection • Surfactants change surface tension and suppress capillary waves • Lower microwave backscatter by 10dB • Slicks are darker than surrounding water Naval Postgraduate School Workshop – 9 August Don Atwood 31 Slick Detection Storm Water Discharge Southern California Images courtesy of Ben Holt Naval Postgraduate School Workshop – 9 August Don Atwood 32 Slick Detection Biogenic Slicks Gulf of Alaska Naval Postgraduate School Workshop – 9 August Don Atwood 33 Slick Detection Accidents Illegal Bilge Dumping Ship Collision off Sri Lanka Naval Postgraduate School Workshop – 9 August Don Atwood 34 Slick Detection Programs under development in U.S., Canada, Norway, Scotland • RADARSAT acquisitions • Oil Spill detection • Airborne surveillance • Support prosecution of violators Naval Postgraduate School Workshop – 9 August Don Atwood 35 Fisheries Monitoring Monitoring illegal fishing is a ship detection problem Naval Postgraduate School Workshop – 9 August Don Atwood 36 Ship Detection • Double bounce of microwaves off ocean and ship yields strong return • Yields bright target against ocean clutter • Automated Identification System (AIS) will permit correlation between detected targets and known ship data Naval Postgraduate School Workshop – 9 August Don Atwood 37 Ship Detection Fishing Fleet Naval Postgraduate School Workshop – 9 August Ship associated with wake Don Atwood 38 Ship Detection 50m resolution 25m resolution 12.5m resolution Improved Resolution permits Ship Identification Wackerman,et.al. Naval Postgraduate School Workshop – 9 August Don Atwood 39 Ship Detection NOAA/NESDIS automated system to detect ships in Alaskan waters SAR-derived ship information available on Web http://www.orbit.nesdis.noaa.gov/sod/mecb/sar/sarproducts.html Naval Postgraduate School Workshop – 9 August Don Atwood 40 Sea Ice • Sea ice scatters microwaves from both surface and ice inclusions • Signal strength and context provide clues to ice concentration and age • Attempts at automation have not been successful • Ice Analysis remains an Art as much as a Science Naval Postgraduate School Workshop – 9 August Don Atwood 41 Sea Ice Sea Ice Grease Ice Bering Sea Chukchi Sea Naval Postgraduate School Workshop – 9 August Don Atwood 42 Sea Ice Ice Edge Sea Ice Leads Bering Sea near Aleutians Naval Postgraduate School Workshop – 9 August Arctic Ocean Don Atwood 43 Sea Ice False-color composite of St. Lawrence Polyna. Radarsat image merged with sea surface temperature (SST) data from AVHRR aboard NOAA-12. Naval Postgraduate School Workshop – 9 August Don Atwood 44 Sea Ice C-band Radarsat-1 image Naval Postgraduate School Workshop – 9 August L-band ALOS image Don Atwood 45 Sea Ice Representative Ice Charts Produced by NIC and NWS http://www.natice.noaa.gov/ Naval Postgraduate School Workshop – 9 August http://pafc.arh.noaa.gov/ice.php Don Atwood 46 Sea Ice Retrospective Studies Ice Parameters derived from Radarsat Geophysical Processing System (RGPS) http://www-radar.jpl.nasa.gov/rgps/products.html Naval Postgraduate School Workshop – 9 August Don Atwood 47 Concluding Comments • Alaska Satellite Facility will actively acquire RADARSAT and ALOS SAR data through the IPY • SAR data is freely available to researchers through NASA support • New tools have been developed to make SAR data more accessible to researchers (e.g. The Convert Tool) • For more information on SAR and data availability: http://asf.alaska.edu http://aadn.asf.alaska.edu Naval Postgraduate School Workshop – 9 August Don Atwood 48 Don Atwood datwood@asf.alaska.edu 907-474-7380 Questions? 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