.c.Gulf Stream


Titles of Investigations:

I.		U. S. Navy Investigations to be Conducted During the SIR-C/X-SAR Experiment

Principal Investigators:

I.		Dr. Donald Montgomery
		U. S. Naval Observatory

II.		Mr. Robert Beal
		Applied Physics Lab/Johns Hopkins University

Site Description:

	The Gulf Stream Supersite is located within corners (42¡N, 75¡W), (36¡N, 65¡W), (30¡N, 73¡W), with nominal center at 36¡N, 73¡W.  This is an ideal site because of its convenient location adjacent to the East Coast of the U. S. and the ease of deploying buoys, ships, and aircraft  to support high quality sea-truth and calibration for the SIR-C/X-SAR passes in 1993-1996.  Such support includes USNS Ago ships and Naval Research Laboratory (NRL) and NAWC/P-3 aircraft.
	Gulf Stream dynamics in this area have been intensively investigated and modeled over the years by the U. S. Navy, other government agencies (i.e., NOAA, NASA, EPA, NSF), and a number of academic institutions (i.e. University of Rhode Island, Harvard University, Woods Hole Oceanographic Institution, Johns Hopkins University).  Models have reached an advanced state and can be used in remote sensing investigations on current-wave interactions with synthetic aperture radar (SAR), with SIR-C/X-SAR L-, C-, and X-band data, and from other present and future spaceborne SAR systems such as ERS-1, JERS-1, ERS-2, ALMAZ, RADARSAT, and EOS.
	The Gulf Stream is a natural laboratory with a variety of oceanic features of basic and applied research interest.  These features include: internal waves, fronts, rips, mesoscale eddies, and others which are continuously shed by Gulf Stream meanders.  ÒSlick-likeÓ and bathymetry-related surface features are also abundant over the continental shelf at the site.  The U. S. Navy and NRL have a number of projects addressing scientific and applied research relating to the Gulf Stream.  For example, the Office of Navy Research (ONR) and the NRL have a five year ARI on High Resolution Remote Sensing ('91-'95) in the Gulf Stream region for understanding radar imaging of submesoscale oceanic features.  The first experiment in this program was performed in September 1991 and a second field experiment is planned for July-September 1993.  Preliminary experiments were conducted during 17-21 July 1990 and 2-4 October 1990.
	The Department of the Interior Mineral Management Service also has a comprehensive three-year program starting in 1992 to understand the oceanography of Cape Hatteras out to 200 km east of the Cape.  The program involves measurements and modeling that should provide additional sea-truth from buoys and ships.  Hence, extensive buoy, ship, and aircraft support will be available during the SIR-C/X-SAR mission for sea-truth and calibration.

Objectives:

I.		a)	The general objectives of the U. S. Navy SIR-C/X-SAR program is to provide data for verifying SAR performance models for measurement of oceanic processes; contribute to the detailed knowledge of aircraft and satellite SAR as a function of frequency, incidence angle, aspect angle, sampling/integration time, other system parameters; and support existing research programs in descriptive and physical oceanography.

		b)	Specific scientific investigations to be conducted include: radar imaging of submesoscale oceanic features, refraction of waves by variable currents, the perturbation of ship wakes by currents and the origin of "slick-like" features. 

		c)	SIR-C/X-SAR PIs from several institutions, including NRL, ONR, NSWC, JHU/APL, NAWC, University of Southern Mississippi, and JPL, are interested in performing scientific and applied research in Gulf Stream Supersite .  These investigators include: G. R. Valenzuela, S. A. Mango, R. P. Mied, A. R. Ochadlick, W. C. Keller, O. H. Shemdin, R. Beal,  F. Monaldo, D. Sheres, P. M. Smith, R. C. Bachman, F. Herr, C. Luther, and R. Goldstein.  Others are welcome to participate in the research as well.

Field Measurements:

	The exact plan for operations and deployment of ground/sea truth instruments during SIR-C/X-SAR passes at Gulf Stream Supersite is dependent on the resources and funding, the amount of which is presently not known.  In the meantime, we can state that high quality ground/sea truth will be provided at the Gulf Stream Supersite from at least one dedicated Navy AGOR oceanographic ship, two Navy airplanes, and a number of National Data Buoy Center (NDBC) buoys which are permanently deployed for the National Weather Service (NWS) off the East Coast of the U. S.  Furthermore, the Minerals Management Service of the U. S. Department of the Interior has a comprehensive field and modeling program that should provide valuable data out to 200 km from the coast from moored buoys, ARGOS drifters, and ship surveys.

Specific resources that should be available during the SIR-C/X-SAR passes in October 1993 are:

	USNS Bartlett (Oceanographic Ship)	Std. meteorological/oceanographic measurements
						ADCP (Acoustic Doppler Current Profiler)
						CTD/XBTs
						Directional Wave Buoy (0.04-0.40 Hz)
						Spar Buoy (1 m - 10 cm waves)
						Lagrangian drifters
						Surface tension

	NRL/P-3 Aircraft			C- and X-band Real Aperture Radar (RAR)
						Ku-band scatterometer
						PRT-5 infrared thermometer
						Laser profilometer
						Multi-spectral video camera
						Ku-band Radar Ocean Wave Spectrometer (ROWS)

	NAWC/P-3 Aircraft			L-, C- , X-band SAR w/ Polarimetric & Spot-light modes
							X-Band Interferometric SAR (DPCA)
							GPS Navigation

	NDBC Buoys (NOAA)			CHL V2 (36.9¡N, 75.7¡W) (C-Man Station)
							41001 (34.9¡N, 73.0¡W) (moored)
							44004 (38.5¡N, 70.7¡W) (moored)
							44014 (36.6¡N, 74.8¡W) (moored)
							44009 (38.4¡N, 74.7¡W) (not permanent)
							44012 (38.8¡N, 74.6¡W) (not permanent)

	Other resources include:

	NRL (Code 4230)			Digital Image Processing Laboratory (DIPL)
							End-to-End SAR processing facility
							Extensive Spaceborne/Airborne Data Base
							SAR Communications System Real Time System

	NAWC (Code 5024)			SAR Data Digital Processing Laboratory
							Corner Reflectors for SAR calibration

	NSWC (Carderock Division)		Endeco buoy, directional wave analysis with Maximum 					Likelihood, Maximum Entropy methods, and Wavelet 					techniques.
							Ship motion sensors, data collection and analysis
							Potential GPS, position and velocity inferred

	Minerals Management Service/Atlantic OCS Region

	Extensive field data from 14 moored buoys, ARGOS drifters, and ship hydrographic surveys for three month periods starting in February 1992 and continuing through 1994 in a region included between 73.5¡W and the coast of Cape Hatteras within latitudes 36.5¡N and 34.5¡N.

Crew Observations:

1)	Crew Journal: Document and locate storm activity, current boundaries, and internal waves.

2)	Cameras: Hercules and Hasselblad will be used to photograph storms, current boundaries, and waves.  Low angle sun glint images are requested.

Coverage Requirements:

	The minimum coverage requirements for the Gulf Stream are four (4) passes.

Anticipated Results:

I.	These investigations will employ a variety of technical approaches, combining SIR-C/X-SAR data with intensive, fine-scale in situ measurements and aircraft-derived data and will contribute to:

	a)		New and/or improved models describing the mechanisms involved in SAR imaging of ocean features and improved definition of the limits of applicability of SAR in a maritime environment. 

	b)	An improved understanding of how current boundaries are imaged with SAR and of the detectability criteria for current boundaries.

	c)	Advances in the understanding of major physical mechanisms driving the generation, propagation, and dissipation of ocean phenomena, such as swell, internal waves, and near surface fine-scale features. 

	d)	Compilation of SAR images and ship wake characteristics correlated with radar, ship, and meteorological parameters.

	e)	Improved understanding of the mechanisms responsible for SAR imaging of wake characteristics at L, C, and X-band radar frequencies in different sea states.

	f)	Evaluation of SAR's potential use in synoptic detection/observation/monitoring.