| Popis: |
A backscatter sensor has been developed for rapidly measuring, in situ, the volume scattering function (VSF) in the back-ward direction. The backscatter sensor uses a bistatic optical geometry to measure backscatter from a small volume of sea-water over a range of scattering angles from approximately 1 15° to 170°. The calibration of the sensor yields a weighted,angular averaged value of the VSF with a centroid located at a scattering angle of about 150°. The backscatter sensor designis based on a sensitive synchronous detector and pulsed, light-emitting diode that has been used at visible and near-infraredwavelengths. The entire sensor package, which includes circuitry for digitizing the signal, is contained in a compact, ruggedhousing. The sensor has been deployed both in towed arrays and in stationary profiling mode. Scattering profiles from tworecent deployments are presented. 1. INTRODUCTION SRI's backscatter sensors were originally developed as part of a suite of instruments designed to measure optical parame-ters of seawater that are of particular importance as "sea-truth" for undersea lidar applications.1 These instruments weredeployed by SRI in support of DARPA's LIDEX experiments in 1982 and 1983.2,3 'fl backscatter sensors have since beenused on several Navy experiments to provide depth profiles of optical backscatter in ocean water'1. We have also successfullyused the backscatter sensor, with minor modifications, to detect marine particles and determine their concentration and sizedistribution.5The backscatter sensor uses a bistatic optical geometry to measure backscatter from a small volume of seawater. Asshown in Section 2, the scattered light received by the detector results from scattering over a range of angles from approxi-mately 1 15° to 170°. The calibration of the sensor, described in Section 3, yields a weighted, angular averaged value of thevolume scattering function (VSF) from the digital signal produced by the sensor. Data taken in ocean waters are presented inSection 4. |
