Under the Sea

Under the Sea

Scientific observation vessel docks in Alexandria to celebrate 200th anniversary.

It all started during Thomas Jefferson’s administration — an ongoing mission to explore strange new worlds, to boldly go where no man has gone before, and to turn a profit. The endeavor President Jefferson had in mind called for an act "to provide for surveying the coasts of the United States." The effort demonstrated a Jeffersonian appreciation for the importance of effective maritime commerce and border defense. For the open seas of a dawning 19th century, the tools of success were accurate charts of shores, waters and hazards to safe navigation.

Now, fast forward two centuries.

Last week the Norfolk-based ship Thomas Jefferson docked at Robinson Terminal South and invited the public to step aboard and see its high-tech underwater surveying equipment. Inside, visitors savored the fruits of a seed planted by Jefferson 200 years ago as a three-dimensional map of New York harbor whizzed through a virtual tour in the pilot room. The ship is operated by the National Oceanic and Atmospheric Administration, an organization that is perhaps better known by its acronym, NOAA. The 208-foot long ship was launched as a Navy vessel in 1991 and then transferred to NOAA in 2003 and christened Thomas Jefferson. As members of the public mingled with dignitaries on the dock, Rear Admiral Samuel De Bow Jr. recalled a recent adventure flying on an Orion P-3 aircraft into the heart of Hurricane Katrina.

"It was an unforgettable experience," said De Bow, who is director of NOAA’s Marine and Aviation Operations. "We were tasked to position the eye of the hurricane."

FLYING INTO THE CENTER of a hurricane is a dramatic yet useful concept to understand the mission of NOAA, whose 200th anniversary celebration brought a gaggle of officers clad in their Navy-inspired gleaming white uniforms to Alexandria last week. Aboard the Thomas Jefferson, Capt. Ray Slagle demonstrated equipment in the ship’s acquisition room and explained how the ship’s computers used acoustic shadows to pinpoint the movement of sediment or the presence of an obstruction. One color-coded image of a sunken pleasure boat cut a strikingly realistic assessment of the underwater piece of archeology.

"Look how you can see the railing," said Slagle, moving his finger along the image. "The sound waves move along an area to take everything in. It’s like mowing the grass, and you want total coverage."

Earlier maps had single-point depths, a function of the single-beam technology that was used until the era of digital mapping made multiple-beam projections a colorful reality. In the acquisition room, where information is gathered from deep below the water’s surface, purple lines represent the deepest points and red markers illustrate the nearest obstructions. Ensuring the safe passage of merchandise requires obstructions to be identified and communicated on the open seas.

"Like Thomas Jefferson himself, Alexandria’s history is tied to maritime commerce," said Mayor Bill Euille during a reception welcoming the ship to the city’s port. "Having good charts today is as important as it was in Thomas Jefferson’s time."

THE ENORMOUS SHIP has a breadth of 45 feet and a draft of 14 feet. Its cruising speed is 12 knots, and it carries a crew of 19. Life aboard the ship has many comforts of home, including an onboard gym, an occasional barbeque lunch and nightly movie viewings in the recreation room with selections including "The Hunt for Red October," "Oceans Eleven" and even "Titanic." Its computers can hold two terabytes of data — that’s 2,000 gigabytes of information. Recent missions for the ship’s crew included charting the movement of a sandbar in the Chesapeake Bay and resurveying hurricane-ravaged Gulf of Mexico.

"We know more about the surface of the moon than we know about the oceans," said Lt. Joe Pica, who is currently preparing to take command of the NOAA ship Okeanos Explorer. "We don’t have that kind of detailed knowledge about the bottom of the ocean, and that’s part of our mission."

The side-scan sonar used by NOAA creates images from returns off hard targets an their associated shadows. Using the echoes created by its targeted output, returning sounds are received by a transducer and transformed into electronic signal. An instrument known as a Klein Towfish can be mounted to the hull of two survey launches or towed behind the main vessel at an altitude of eight to 18 meters off the bottom. NOAA’s mission to provide maritime information to the Department of Commerce is an important goal, yet the ship’s crew cannot help but daydream about the stories waiting underwater.

"There are still pirate ships out there," said Capt. Slagle. "And don’t forget about the Spanish Galleon ships."