A Buoyancy-Controlled Lagrangian Camera Platform for In Situ Imaging of Marine Organisms in Midwater Scattering Layers

This paper presents the design, development, and field results of an autonomous, deep-submergence, depth-controlled Lagrangian camera platform. Called the "Driftcam," this relatively small system has been developed to freely probe midwater acoustic-scattering layers while being used in combination with active acoustics on a nearby research vessel. The system uses a low-light video camera and illumination system installed within a polished borosilicate spherical housing. A novel buoyancy engine, using pressure feedback control, facilitates active depth correction to a maximum depth of 1500 m. Embedded computers command the camera, lighting, and depth control. The vehicle is an acoustic modem for bidirectional communication to the surface tender. Radio direction finding and an Argos satellite beacon aid in surface recovery. In addition, the system is highly portable, measuring 1.5 m in total length with a mass of 85 kg, and has the potential to increase the visual sampling of midwater communities by reducing operational costs. All aspects of the system are discussed with focus given to design, testing, and performance of the buoyancy engine. Preliminary results are also presented for deployments into scattering layers in the Guaymas Basin of the Gulf of California, Mexico, showing the utility of the Driftcam system in the field.