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BACIMO ’05 Conference Session 8: EM/EO Propagation Monterey, CA, 14 October 2005. Results on the Bulk Modeling of C n 2 Over the Ocean from an Ongoing Experiment. Paul Frederickson and Kenneth Davidson Naval Postgraduate School Monterey, CA Stephen Hammel and Dimitris Tsintikidis
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Session 8: EM/EO Propagation
Monterey, CA, 14 October 2005
Results on the Bulk Modeling of Cn2 Over the Ocean from an Ongoing Experiment
Paul Frederickson and Kenneth Davidson
Naval Postgraduate School
Stephen Hammel and Dimitris Tsintikidis
Space and Naval Warfare System Center
San Diego, CA
The critical parameter in quantifying the effects of optical turbulence on EM/EO propagation:
Scintillation: high-frequency signal intensity variations
Image degradation: image blurring, image “dancing”
Laser beam distortion: beam spread, beam wander
Above effects can degrade target detection/identification, intelligence collection, laser target designation, potential HEL use for ship-defense & other military applications.
What is Cn2 & why is it important?
Cn2 = 1 10–14
Cn2 = 1 10–16
Mean met measurements much easier and cheaper to obtain than single-point turbulence or optical propagation measurements of Cn2.
Bulk models can be used to construct Cn2 climatologies from historical meteorological data sets.
Can be used in numerical weather prediction models to produce forecasts of Cn2 conditions.
Can be used in operational Tactical Decision Aids (TDA’s) with real-time, in situ measurements to optimize optical system performance for current environment (e.g. EOSTAR).
Importance of Bulk Cn2 Models
To determine the accuracy of the current NPS bulk Cn2 model under different environmental conditions.
To develop improvements in the current bulk Cn2 model.
Objectives of the Study
7.2 km path
Turbulent: Estimated Cn2 from single-point sonic temperature fluctuation measurements (10 Hz) on NPS buoy.
Scintillation: SSC-SD determined Cn2 from measured amplitude fluctuations in near-IR (1.06 m) signal transmitted along 7.2 km path over San Diego Bay.
Cn2 Determined by Three Methods
Wind Speed Variations
Bulk model Cn2 estimates agree well with scintillation measurements in unstable conditions, underestimate scintillation measurements in near-neutral conditions and do not agree as well in stable conditions.
Air-sea temp difference & wind speed dependence in bulk-scintillation Cn2 comparisons indicate empirical stability functions used in bulk model need improvement, especially in stable conditions.
Will have several more months of data to examine in future to determine better comparison statistics and hopefully improvements to bulk model.
Bulk Cn2 Estimates
Possible Wave Influence?
Mean Atmospheric Parameters