Calibration of a high frequency monostatic acoustic echosounder
Cherry, David R.
Walters, Donald L.
Davis, David S.
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Atmospheric turbulence degrades a coherent laser beam when it propagates through the atmosphere. Measurement of the atmospheric turbulence provide insight into to underlying mechanisms that produce optical turbulence and suggest possible means to overcome or circumvent the effects of such turbulence. A variety of acoustic, optical and thermal probe instruments provide measurements of atmospheric turbulence. Of these, the acoustic echosounder can measure atmospheric density and velocity irregularities. During the course of previous work, questions arose concerning the calibration of the NPS echosounder. The echosounder appears t detect a higher level of atmospheric turbulence than do other instruments used at the same altitude. This resulting overestimation of atmospheric turbulence could significantly influence programs such as the Advanced Electro-Optic Site (AEOS), a proposed 4 m telescope to be built in Hawaii. This thesis will attempt to identify key components contributing to the sounder calibration including the transducer transmitting and receiving efficiencies as well as their dependence on pressure and atmospheric density. Additionally a modified acoustic echosounder equation will be developed which more accurately profiles the atmospheric turbulence measured by such a sounder.
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