NOAA mapping ship helps find JFK Jr.'s plane
When the Coast Guard needed advanced systems technology to help locate the wreckage of John F. Kennedy Jr.'s downed plane, it contacted the National Oceanic and Atmospheric Administration, which sent the Rude, a ship that uses side-scan sonar to map the ocean floor.
By Frank Tiboni
GCN Staff
When the Coast Guard needed advanced systems technology to help locate the wreckage of John F. Kennedy Jr.'s downed plane, it contacted the National Oceanic and Atmospheric Administration, which sent the Rude, a ship that uses side-scan sonar to map the ocean floor.
The 90-foot vessel is equipped with three systems that use commercial hardware and software to process sonar images, said Frank Colohan, Navigation and Communications Branch chief of NOAA's Atlantic Marine Center in Norfolk, Va., the Rude's home port.
The Coast Guard asked for the Rude's help after it began searching for Kennedy's Piper Saratoga II TC off the coast of Martha's Vineyard, Mass., late June 16.
Kennedy, his wife, Carolyn Bessette Kennedy, and his sister-in-law, Lauren Bessette, died when the plane he was piloting crashed. Divers found their bodies and part of the plane last week.
The Rude had docked earlier on the evening of the crash at Montauk, N.Y., after mapping the ocean floor off Long Island, N.Y., Colohan said.
'The Rude was producing nautical charts to ensure safe navigation in that area,' Colohan said. 'But the technology it uses to perform mapping every day makes it exceptional for search and rescue.'
When the Rude received the call, it quickly set out. With a cruising speed of 10 knots, the ship reached the Coast Guard's search-and-rescue area at 7 p.m. July 17, and began mapping the ocean floor that evening, Colohan said.
The Whiting, another NOAA vessel, joined the effort July 19, he said.
The steel-hulled Rude uses three basic systems to map the ocean floor: a vertical echo sounder, a shallow-water multibeam sonar system and an analog side-scan sonar system with digital processing, said Dave Pritchard, technical adviser for the System Support Branch of NOAA's Hydrographic Surveying Division..
The Rude primarily used the analog side-scan sonar system to help locate the wreckage of the plane in 116 feet of water about seven miles off the coast of Martha's Vineyard.
A 260-TH image-correcting side-scan sonar known as the towfish did sweeps of the ocean during the effort. The towfish, from EdgeTech Inc. of Cataumet, Mass., has two identical transducers that send out a fan-shaped pulse of energy that reflects off an object back to the transducer, Pritchard said.
Under the sea
The towfish, via an electromagnetic cable, connects to a recorder in the pilothouse of the ship. When the pulse comes back, it goes through an analog interface to an Isis sonar data-processing computer from Triton-Elics International Inc. of Watsonville, Calif.
Isis acquires and processes image data from both the side-scan sonar system and the shallow-water multibeam sonar system. Isis collects the data and archives it in a RAID storage system. Final processing of the sonar images taking place on SGI Indy workstations running Irix, Pritchard said.
The Rude tows the sonar in a predetermined line using a hydrographic survey package called Hypack from Coastal Oceanographics Inc. of Middlefield, Conn. Hypack, which runs on a 400-MHz Gateway Inc. PC under Microsoft Windows 95, plans and conducts the towfish's search path. NOAA and Coast Guard officials refer to this part of the process as mowing the grass, Pritchard said.
A Hydrographic Processing System, consisting of two Pentium PCs running Windows NT 4.0, collects the data from Hypack. The system also uses MapInfo geographic information systems software from MapInfo Corp. of Troy, N.Y., and Vertical Mapper contour, modeling and display software from Northwood Geoscience of Nepean, Ontario.
MapInfo and Vertical Mapper let the Rude's hydrographer visualize, correlate and analyze data. A Hewlett-Packard DesignJet 750 color plotter captures and prints the graphical representations of the data, Pritchard said.
After the system processes the sonar data, it generates a mosaic of the ocean floor. The SGI workstation lets users create georeference points for objects on the sea floor by clicking on an image with the mouse, he said.
When an object gets hit by sonar, it casts a shadow. The SGI workstations can measure the length of the shadow, which corresponds to the height of the object above the sea floor, Pritchard said.
The Rude's advanced systems do not come cheap, Colohan said. The total price tag was about $120,000'$70,000 for the side-scan sonar system and about $50,000 for the Isis system, he said.