Validation of the installation of CTD sensors on an AUV

Autonomous underwater vehicles (AUVs) will allow oceanographers to collect more data, at lower cost, than traditional means. To achieve widespread acceptance within the oceanographic community, AUVs must deliver data of comparable quality to that collected by conventional means. The fundamental measurements for physical oceanography are the pressure, temperature and electrical conductivity of water over a range of locations and depths, measurements that are usually referred to as "CTD" for conductivity, temperature, and depth. This paper discusses the accuracies required for measuring water conductivity, temperature, and pressure for physical oceanographic applications and describes the method used to validate the CTD package on a specific AUV. Temperature measurements made in the deep ocean with the Odyssey-II AUV agreed to within 0.001 degrees Celsius to those made with a standard oceanographic CTD package. This work represents a first step in the process of defining protocols for validating CTD in an AUV. The approach used allow us to place a quantitative upper bound in the perturbation of the CTD measurements by the Odyssey II AUV.