They are underwater research robots – so to speak. They receive their orders from an on-board computer that uses a GPS system to create their instructions. They belong to the EPA-America and University of Minnesota – Duluth and carry the names of two famous characters from Henry Wadsworth Longfellow’s Song of Hiawatha; Nokomis (daughter of the moon) and Gitche-Gume (Ojibway for big water.)
They look like torpedoes, but they are gliders—autonomous underwater vehicles that collect data as they travel through the lake, while programmed to GPS coordinates. While underway, the gliders are continuously measuring things like water temperature, backscatter (a metric for the amount of particles in the water), chlorophyll, and CDOM (colored dissolved organic matter.)
These 52-kilogram devises are self-propelled, using buoyancy created by an air bladder in the glider’s tail and a piston to fill the nose cone with water. The combination causes the glider to make a 26-degree descent. It is able to dive as deep as 650 feet. An altimeter monitors the movement and when the glider reaches that depth—or if it gets closer than 10 feet from the bottom of the lake—it climbs back up to 18 – 20 feet below the surface of the water.
Scientists stay in contact with the glider as it collects valuable information on Lake Superior – or other Great Lake lakes. At certain preset GPS waypoints and once every six hours the submersible comes to the surface and, like the alien of E.T. fame, “phones home.” Home is wherever the researchers are and the information is sent via the Internet. “It text messages us,” says project staff, if all is not well.
The check-ins are important, as none of the data collected can be sent while the gliders are underwater. The message lets researchers know that the glider has been working properly, recording all the data it is supposed to when it is out of contact. “It says ‘here I am’ or ‘I’m not okay, come get me.”
For real time location of these gliders click here.