Feature ArticleSurveying With the SeaBED-Class AUV Mola Mola
By Max Woolsey
Dr. Arne-R. Diercks
Dr. Vernon Asper
Undersea Vehicle Technology Center
National Institute for Undersea Science and Technology
University of Southern Mississippi
Stennis Space Center, Mississippi
Mola Mola, named for the ocean sunfish with which it has a similar form factor, is a SeaBED-class AUV, which means it is designed to operate safely at low speed near the seafloor. Since the National Institute for Undersea Science and Technology (NIUST) acquired the Mola Mola in May of 2009, the institute has used it to collect data during transects over coral and performed a shipwreck survey. It has worked both independently and in tandem with Eagle Ray, NIUST’s larger and faster AUV. Eagle Ray can complete broad initial surveys that may be followed up by more focused Mola Mola surveys after identifying points of interest. This two-phase survey approach was successfully carried out during the shipwreck study.
The Mola Mola AUV was designed and built by Dr. Hanumant Singh and his team at Woods Hole Oceanographic Institution (WHOI). It has an upper and lower torpedo-shaped pod separated by two vertical struts. The upper pod is positively buoyant, containing the main electronics housing and syntactic foam. The lower pod provides ballast from a lithium-ion battery pack and sensors. This separation of buoyancy leads to passive stability with regard to pitch and roll. Maneuverability is provided by two horizontal thrusters, port and starboard, and a vertical thruster.
Typical survey parameters for Mola Mola are an altitude of three meters and speed of 0.15 to 0.25 meters per second, with a maximum depth capability of 2,000 meters.
The Mola Mola AUV being lowered toward the water on a quick release during a cruise in September. (Photo courtesy of Ken Sleeper, University of Mississippi)
Several institutions are currently using SeaBED-class vehicles for photo, multibeam and water-column chemistry studies. The vehicles are each customized with a suite of sensors for their particular operational tasks. Many of the surveys conducted by SeaBED vehicles are regional habitat studies in which photomosaics are created for population analysis. Examples of these missions include those performed by the NOAA Northwest Fisheries Science Center and the Australian Center for Field Robotics at the University of Sydney. Other studies have involved deep-sea plume detection and other water-column data collection from WHOI’s SeaBED variants Puma and Jaguar, which are capable of operating in depths up to 6,000 meters.
The primary task of Mola Mola is to survey specific targets as deep as 2,000 meters. These targets include areas of gas hydrate concentration, shipwrecks and anomalies spotted during broad-scale habitat studies carried out by Eagle Ray. The Mola Mola was ordered essentially as a “base model” SeaBED, with the intent of enhancing this base design to fit the needs of its primary uses. Its suite of navigation sensors included a Teledyne RD Instruments (Poway, California) Doppler velocity log (DVL), a Paroscientific (Redmond, Washington) depth sensor and long-baseline (LBL) navigation capability provided by a WHOI Micro-Modem. Attitude and heading were measured using the tilt sensors and magnetic compass internal to the DVL. The vehicle was equipped with a down-facing camera in the forward end of the lower pod and a flash unit in the rear of the pod. To continue this article please click here.
Max Woolsey graduated from the University of Mississippi in 2008 with an M.S. degree in electrical engineering. While at the university, he spent time building an autonomous robot, designing and testing components for an X-band radar system and researching parallel computing techniques. As an AUV engineer, he now programs, modifies and operates the National Institute for Undersea Science and Technology’s AUVs.
Dr. Arne-R. Diercks received a master’s in geology and paleontology from the University of Hamburg, Germany, in 1990 and a Ph.D. in geological oceanography from the University of Southern Mississippi in 1995. During his professional career, Diercks has studied coastal surface currents with high-frequency (HF) radars and helped with the implementation of the U.S. National HF Radar network. He also designed and built the first neutrally buoyant autonomous sediment-collecting device for deep-ocean climate studies.
Dr. Vernon Asper is a professor of marine science at the University of Southern Mississippi and the director of the Undersea Vehicle Technology Center division of the National Institute for Undersea Science and Technology. When not at the university, Asper works in Antarctica, where he studies the carbon budget of the Southern Ocean in collaboration with scientists from many institutions from around the world.