Survey ships sail into history

The Navy has started to deploy the most computerized oceanographic survey ships in its history, with the Navy standard Tactical Advanced Computer-4 (TAC-4) contract providing most of the computing muscle for this new class of T-AGS 60 ships.

Not only do the central computers in the T-AGS 60 class handle on-board processing for 11 major surveying instruments, they literally steer the ship, according to Dan Depner, a geophysicist at the Naval Oceanographic Office, Stennis Space Center, Miss., who helped develop the ships' mission electronic suite.

"The captains were a little skeptical at first about using the central computer for steering," Depner said. "But it's much more accurate when we're doing tracks, especially in rough weather."

Two Hewlett-Packard Co. 9000/755 workstations acquired from the contract serve as the central mission computers, Depner said. They receive data from the surveying instruments through two 486/66 PCs hooked up to two 16-channel digiboards.

A multibeam echosounding system—a bathymetric sonar—feeds its signals into a Sun Microsystems Inc. workstation, "which then spits out the data over a copper wire to the central computer," Depner said.

The three T-AGS 60 ships—the USNS Pathfinder, the Sumner and the Bowditch—are built around multiple local-area networks, two made of copper cable and the other of optical fiber.

These networks carry data from the central computers to a system that refines the raw instrument data, a package that includes two HP 9000s and two Sun SPARC 10s, Depner said. The ships are also equipped with three SPARC 10s to help process acoustic data.

Accurate positioning information, essential to the surveys that the oceanographic vessels conduct, comes from a built-in Global Positioning System, with all ships in the class carrying their own differential GPS reference transmitter for even greater accuracy. If differential GPS signals are unavailable, the ships' crews would install this reference transmitter at a surveyed point on shore, providing corrections to the ships via a data link.

Science Applications International Corp. developed the Integrated Survey System Software that helps manage the data collected by the surveying instruments. This software manages the collection, storage and processing of data from the GPS, the multibeam echo-sounder and other real-time sensors. An X Window system lets scientists manage and view the data collected by the sensor as well as lay out precise survey tracks.

Though the T-AGS 60-class ships are multiple-mission ships capable of handling deep-ocean and littoral surveys, Depner said current data collection efforts focus on littoral areas, in keeping with a change in the overall Navy mission to focus more on close-to-shore operations.

Data collected by the survey ships goes to many users, including the Defense Mapping Agency, which uses it to help make charts, Depner said. The survey ships generally store data and then "dump" it after returning from a cruise, but Depner said the oceanographic office plans to install a secure 56 kilobit/sec satellite link on the survey ships that will allow access to shore-based computer systems.

Adm. Jeremy Boorda, the chief of naval operations (CNO), recently signed a new policy directing Navy oceanographers to emphasize their research on near-shore areas. Instead of hunting for Red October submarines, naval forces will be increasingly engaged in supporting nearby land forces and will need data to support safe, near-shore operations.

"The era ushered in by the end of the Cold War requires a new focus," Boorda said in recent testimony before Congress. "The high-tech systems we use in the Navy today require sophisticated and timely environmental information, or they simply won't work."

The CNO's new policy for naval oceanography also directs that a Navy oceanographic fleet of no less than eight ships be maintained. "Eight is the bottom line to do the work needed to be done," Boorda said.