Abstract
A ship towed gamma ray spectrometer has been developed to continuously map the distribution of radionuclides on the seafloor following the release from the Fukushima-Daiichi Nuclear Power Plant. The device enables continuous measurement of gamma emitters such as 137Cs and 134Cs to be made over long distances. In order to geo-reference the measurements made, accurate localization of the system is necessary. In this paper, a method to determine the location of the instrument is developed based on simulations using a two phase lumped mass model of the towed system. The effects of environmental parameters such as the frictional coefficient of the seafloor, and underwater currents on the position of the towed system are assessed in order to bound uncertainty in the position estimates. We demonstrate the accuracy of the model by comparing depth measurements of the towed system with acoustic measurements of bathymetry during towed deployment at sea.
