A Sea Trekking Rechargeable Instrumented Drifter (STRIDR)

We describe the development of STRIDR, a low-cost drifter developed for DARPA’s Ocean of Things (OoT) program. OoT focuses on developing affordable, multi-sensor drifters deployable at large scales for high resolution sensing at the ocean surface. We review the design process and requirements driving our design decisions, including environmental impacts. We describe the various system configurations, provide an overview of processing, and results of testing to date, including comparisons to other drifters.

STRIDR is a small, low-cost Lagrangian drifter with a standard suite of sensors including GPS, a 10–DOF inertial measurement unit, a microphone, and temperature and pressure sensors. Optional sensors include a sky pointing camera, a hydrophone, a radio frequency detector, or a conductivity sensor. On-board processing produces environmental measurements including drifter location and surface current estimates, wave statistics, atmospheric and ocean surface temperature, barometric pressure, wind speed, humidity, and cloud cover. STRIDR’s LINUX based operating system runs on a low-power ARM processor and includes a Python based analysis environment. This permits developing and deploying additional processing algorithms using modern development tools and APIs.

With its small size and rugged construction, STRIDR is easily deployed from a variety of platforms. While STRIDR is designed to be expendable and minimize environmental impact, including elimination of almost all plastic, it incorporates several design features to extend its lifespan. A lithium polymer battery is recharged by four solar panels attached to STRIDR’s stabilizing drifter arms. This extends drifter life and allows bursts of high-power processing, enabling a broad and adaptable mission set.