Undersea robot aims for 3-D image of BP oil plume

WASHINGTON, USA: Scientists geared up on Wednesday for a 12-day trip in the Gulf of Mexico with an undersea robot they hope will capture 3-D images of oil plumes from the BP spill.

Oceanographers and others have been monitoring the plumes of oil, gas and dispersant chemicals coming from the broken BP wellhead since soon after the April 20 explosion on the Deepwater Horizon drilling platform.

An underwater video camera shows the oil gushing from the wellhead on the sea floor, and aerial and ship observations have charted where the spill has drifted on the water's surface.

But the exact location and the extent of oil and other chemicals in the water column have been harder to determine.

The scientists' robotic vehicle would try to figure out how big the plume is, where it is and what it is made of, said Christopher Reddy, director of the Coastal Ocean Institute at Woods Hole Oceanographic Institution.

"The technology that we're bringing to bear is perhaps more suited to interrogate the size, shape and chemical composition of those plumes than what traditional oceanographers have been using," Reddy said by telephone from St. Petersburg, Florida.

The robot, called Sentry, can be put over the side of a research vessel for 14 to 18 hours at a time, with a mass spectrometer that can "sniff for oil," Reddy said.

CIRCLING THE PLUME

Unlike robotic vehicles that are directed remotely by computer, Sentry can change course by itself -- like a bloodhound following a scent -- to track oil, gas or other hydrocarbons leaking from the sea bottom, Reddy said.

The Sentry AUV (autonomous underwater vehicle) is on the research vessel Endeavor, a 184-foot (56-metre) oceanographic ship owned by the U.S. National Science Foundation and operated by the University of Rhode Island.

Reddy is among some 30 scientists and crew who plan to set off from the Florida Gulf coast on Thursday for the area near the spill, focusing on the so-called southwest plume that has been seen about 20 miles (32 km) south of the wellhead.

Instead of sensors dropped over the side of boats almost like fishing lines, which can observe only a small portion of the plume, Sentry would move around on its own to circle the oil, move up and down or go through it.

"At the end of the day, we'll have a three-dimensional, almost holographical image of the plume," Reddy said.

The hastily arranged voyage has meant packing lots of scientific equipment and other supplies aboard Endeavor to make the most of the 10 days to be spent in the area of the spill, Reddy said.

One logistical issue is fresh water. Vessels like Endeavor usually can purify sea water for drinking and other uses, but that is impossible in the spill area. The ship could go outside the spill site or even dock to get fresh water, but that would mean less time for observation. Instead, Reddy said, water will be rationed.

More information about Sentry is available online here.