TECHNOLOGY AREAS: Air Platform, Sensors, Battlespace

ACQUISITION PROGRAM: SPAWAR PMW-180 Operational Effects Program (OEP)

OBJECTIVE: Develop an instrument system to be deployed on a towed drone for the measurement of air-sea fluxes, dissipation rate, wave height, and aerosol characteristics.

DESCRIPTION: The region immediately above the ocean surface is generally inaccessible to most measurement techniques, while it is an important region of high gradients and intense air-sea interactions. The objective is to instrument an existing Navy Meggitt TLX-1 low level height-keeping towed target to obtain measurements at approximately 30 feet above the ocean while the tow aircraft is at a safe higher altitude. The TLX-1 towed target is a streamlined eight inch diameter, five foot long tube with a hemispherical nose with 170 watts at 28 VDC and as payload capacity of 65 pounds. Within these size, power and weight parameters of a TLX-1 towed target, it is desired to obtain very fine-scale measurements of relevant thermodynamic atmospheric variables (three wind components, temperature, and humidity) together with ocean wave height and sea spray aerosol characterization. The technical challenges include development, integration and characterization of the sensors for wind, temperature, pressure, etc. in terms of frequency response and spatial resolution and the measurement of ocean wave spectra, white capping fraction and aerosol loading. An important variable in air-sea interactions, especially at high winds, is the rate of dissipation of kinetic energy. With high-fidelity sensors, this can be estimated from the power spectral level of the velocity components. With simultaneous wave height measurements, the phase-resolved wind and related fields can be determined. Aerosol characterization will enable the source function to be determined over breaking waves. Quantification of measurement errors is critical.

PHASE I: Proof-of-concept effort should result in a description of a high fidelity air-sea-wave-aerosol interaction sensor suite for application on a TLX-1 towed target and analysis of the feasibility of commercializing the final product.

PHASE II: Develop and demonstrate a fully capable instrument suite for use on a Navy provided TLX-1 towed target. Thoroughly test the system, and successfully demonstrate its functionality. Develop a plan for transitioning the package to commercial use. Develop a commercialization (Phase III) plan, including descriptions of potential customers, missions, demonstrations and transition efforts to be performed.

PHASE III: Transition the system into an operational air-sea-wave interaction instrument package to include documentation, calibration and other tools and spare parts. Support sea-wave interaction instruments integration for government customer-specified platforms. Finalize requirements for a sea-wave interaction system that would allow its utilization by various research aircraft.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Benefits to researchers and to research monitoring programs are inherent in the objective of the proposed effort. Commercial applications include oil spill assessment, radar ducting assessment and hurricane reconnaissance.

REFERENCES:
1. Edson, JB and CW Fairall 1998: Similarity relationships in the marine atmospheric surface layer. J. Atmos. Sciences, vol 55, 2311-2328.

2. Hristov, T., C. A. Friehe and S. Miller, "Wave-Coherent Fields in the Air Flow over Ocean Waves - Identification of Cooperative Behavior Buried in Turbulence,'' Phys. Rev. Letters, 81, no. 23, 5245-5248 (1998).

3. Information of the TLX-1 Towed Target can be found at the Meggitt Defense Systems web site at www.meggittdefense.com.

KEYWORDS: Marine Atmospheric Boundary Layer, surface radar ducting, optical propagation, aerosol measurements, ocean wave measurements, and aircraft towed instrument platform

** TOPIC AUTHOR (TPOC) **

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