Autonomous underwater vehicles (AUVs) have recently become available and popular as stable and reliable platforms for oceanographic instrumentation and for conducting surveys of the water column over a small region. We are in the process of acquiring an Odyssey III class AUV from Bluefin Robotics (expected delivery is summer 2002). One of our long-term goals is to develop this AUV as a platform to study fine-scale to small-scale processes in the ocean. Our main objective in this proposal is to measure velocity-microstructure from Odyssey III AUV, and we are the first user group attempting to make such measurements from this class of Bluefin vehicles. In order to obtain the turbulent kinetic energy (TKE) dissipation rate we must meet two distinct goals: (1) determine that this AUV is an appropriate platform from which to make microstructure measurements, and (2) adapt an existing conductivity and temperature microstructure package to measure TKE dissipation rate by adding shear probes. To meet goal (1), we must: (a) verify that the platform is either noise-free in the frequency band of interest, or that the noise is narrow-band and can be removed from the signal, and (b) determine the flow distortion of the vehicle in order to know how far forward of the AUV nose the microstructure sensors must be placed in order to sample the free stream. At present, neither we nor the AUV manufacturer (Bluefin Robotics) have a quantitative measure of vehicle noise and of flow distortion around the vehicle. The vehicle noise will be evaluated by measuring acceleration of AUV, and flow around the AUV will be examined from numerical techniques. The existing microstructure package, "MicroSoar" will be upgraded with shear probes along with appropriate hardware modifications to obtain microscale velocity fluctuations.
