A Low-cost, Expendable Shallow Water Profiling Float with Improved Capabilities

Floats are underwater drifting buoys and are being used extensively for oceanographic measurements. For example, the Argo program employs over 4000 floats annually for ocean observation and they measure temperature, pressure and salinity that contributes data to climate change studies. The program also employs biogeochemical floats that measure chlorophyll, Nitrate, Oxygen, pH and suspended particles in the ocean water column. Nevertheless, they are expensive when sourced in small quantities and has limited capabilities per float. Availability of low-cost sensors and electronic modules have made it possible to drive down the cost of floats. In this paper we report design and development of a low-cost float with enhanced capabilities for use in oceanographic research. Apart from the traditional sensors like temperature, pressure and conductivity, the shallow water profiling device (SPD) described in this paper is equipped with an echo sounder to measure bathymetry and a hydrophone to measure the ambient noise. The system has a depth capability of 200m and an endurance of 100 profiling cycles. Pre-processed data are transmitted via a satellite link and presented to the end user through a graphical interface. Results from experiments conducted in local waters are provided in support of the equipment capability. The low cost of the system means it can be expendable at the end of its life, if desired to reduce the environmental impact arising from its recovery operations.