The sea glider is an autonomous underwater vehicle (AUV) developed
collaboratively by scientists and engineers at the University of Washington
(UW) School of Oceanography and Applied Physics Lab (APL). It represents a
recent trend in oceanography away from relatively expensive ship-based
research. While traditional observational methods facilitated by ships,
submarines, and remotely-operated vehicles will continue to help us understand
specific parts of the oceans, autonomous vehicles make thorough exploration of
the vast ocean volumes conceivable. The sea glider flies through the water with extremely modest energy requirements using changes in buoyancy for thrust coupled with a stable, low-drag, hydrodynamic shape. The glider alters its buoyancy with the mechanical equivalent of a fish bladder and navigates by using the resultant descending or rising motion to steer a specified compass course. Designed to operate at depths up to 1000 meters, the hull compresses as it sinks at the same rate that seawater compresses, thereby avoiding additional buoyancy adjustments. The sea glider's cylindrical hull is a series of arched anodized aluminum panels separated by ring frames. The hull is surrounded by a fiberglass fairing to give it a low drag shape. Because of their high efficiency, these small, free-swimming vehicles can gather endure for months at sea and transmit the data they collect via satellite in near real-time (during each surface interval).
The sea glider can acquire oceanographic measurements traditionally collected by research vessels or moored instruments, but at a fraction of the cost. It can survey along a transect or profile at a fixed location, and can be commanded to alter their sampling strategies throughout a mission. In fact, by providing the glider computer with information about the bottom topography, the glider could conceivably be deployed and recovered from a coastal pier, but gather data throughout an entire ocean basin!
The sea glider is 1.8 m long and weighs 52 kg, a size and weight that allow easy launching and recovery by two people from a small boat. It can travel at slopes as gentle as 1:5 or as steep as 3:1. At gentle glide slopes the vehicle transits most efficiently, while steeper slopes are used to maintain position and act as a "virtual mooring." After each dive the sea glider dips its nose to raise its antenna out of the water. It determines its position via GPS, calls in via Iridium data telemetry satellite, uploads the oceanographic data it just collected, then downloads any new instructions. In the near future, it will be possible to conduct observational programs from land by coordinating a fleet of gliders.
Find more information at: http://www.apl.washington.edu/projects/seaglider/summary.html