U.S. Naval Research Laboratory researchers from the Ocean and Atmospheric Science and Technology Directorate along with the Scientific Development Squadron (VXS) 1's UV-18 Twin Otter conducted airborne research last month in Homer, Alaska. The team's objective was to measure bubbles using Lidar, a laser system for measuring the ocean properties. Improved understanding of bubble fields has many applications, including radiance, surface properties, and characterization of the ocean's surface.
NRL's Scientific Development Squadron (VXS) 1 and Ocean Sciences Division researchers onboard the UV-18 Twin Otter fly over the Chugach Islands Jan. 31 to determine ocean bubble fields using the NRL Lidar and multi-wavelength camera. Quantifying the oceanic whitecaps and subsurface bubbles is important to the Navy's oceanographic models to characterize the long-term evolution of the ocean environment because bubbles are the primary way the atmosphere and oceans exchange heat, momentum, and gas.
Current remote sensing techniques for ocean research rely primarily on passive observations at different wavelengths, including, visible, infrared, and microwave to estimate water leaving radiance and surface properties, such as sea surface temperature, salinity, and wind. Lidar is fundamentally different because visible light penetrates well into the water body and it has the unique capability to provide a vertical profile of ocean properties.
NRL's Lidar system consists of a self-contained unit installed in a weatherproof enclosure, designed to be mounted on the Twin Otter's research compartment with the laser pointed down into the water. The project required high surface winds to create bubbles, or breaking waves, and good flying weather. The team deployed two underwater echo sounders and flew over the same area with the new airborne Lidar system. The system was built with internal NRL basic research funding and is also a technology demonstrator for Josset's Office of Naval Research CubeSat and Bureau of Safety and Environmental Enforcement oil projects.