Miniaturized wave measurement drifter for undersatellite calibration and validation network

As the number of satellite missions observing the ocean increases, reliable and cost-efficient tools are needed to accurately calibrate and validate the expanding network of space sensors. Traditionally, sea surface buoys have been used to measure various oceanic and atmospheric parameters; however, when it comes to subsatellite data related to processes occurring in the upper ocean layer, the use of traditional buoys is not always straightforward. The properties of different sensing bands, acquisition rates, sensor time and spatial resolution must be taken into account to properly match satellite remote signals with in-situ buoy measurements. This necessitates the creation of specialized sensors dedicated to measuring sea surface parameters, such as directional wave spectrum, sea surface current, and temperature, that have the most significant impact on remote sensing signal formation.

The Miniaturized Electronics Lagrangian Oceanographic Drifter (MELODI) program has developed a specialized electronic platform that enables the rapid construction of miniaturized, cost-effective sea surface drifters for subsatellite calibration/validation tasks. The hardware can be configured with different set of onboard sensors, data preprocessing/compression modules, and satellite-enabled communication systems to allow for the real-time collection and transmission of data. Preference is given to the extensive use of environmental-friendly and biodegradable materials, as well as to the implementation of an industrial fabrication process to reduce the time and costs of mass buoy production.

Our study addresses the specificity of measurements obtained from small-scale platforms, such as directional wave spectrum distortions due to intrinsic noise, reduction of wind impact on the buoy drift, oceanographic data preprocessing and compression for IOT small satellite messaging, etc. We present the first results of an in-situ validation campaign (7 day long) for a buoy created specifically for cal/val of the Surface Water and Ocean Topography (SWOT) mission. This miniaturized drifter (~15 cm in diameter) has onboard accelerometers, gyroscopes, magnetometer, GPS sensors and is dedicated to the systematical measurement of significant wave height, directional wave spectrum and sea surface current. The satellite-based communications allow real-time reporting every 15 min, with an expected autonomy of 2 months up to 1 year depending on the configuration and reporting frequency.

We expect that the present results,  electronic platform, and proposed algorithmic and technical solutions will allow enabling the development and implementation of a more robust network of observational drifting buoys for calibration and validation of ocean monitoring satellite missions. 

The work was supported by the project “Development of marine services using space data and IOT technologies by Kinéis” funded by IFREMER and Kinéis.