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CSS Diver Display Technology Locates Space Shuttle Debris


25 April 2003

By Dan Broadstreet, Coastal Systems Station Public Affairs

PANAMA CITY, Fla. -- Upon encountering some of the most challenging diving conditions he'd ever experienced, Naval Sea Systems Command's Supervisor of Salvage and Diving (SUPSALV), Capt. Jim Wilkins contacted Naval Surface Warfare Center Dahlgren Division's Coastal Systems Station (CSS) and requested the deployment of two prototype Limpet Mine Sonar (LIMIS) systems to assist in finding the STS-107 Columbia space shuttle debris.

LIMIS systems are hand-held sonar prototypes used in combination with the Miniature Diver Display System (MDDS) to conduct underwater search and identification operations. Limpet mines are small, explosive, attack mines that are magnetically attached to ships' hulls, usually near the rudder and propeller systems. Wilkins, the Operational Commander of the debris search and recovery mission, also requested that CSS send supporting technical expertise to aid in the deployment of the LIMIS systems. CSS's Human Factors Engineer Ron Honaker and Senior Electronic Systems Engineer Bill Olstad were on site at the search area for two weeks with the systems and supporting materials. The call to assist provided a unique opportunity to test the systems in a near zero visibility environment.

The mission required nine dive teams deployed each day in the Toledo Bend Reservoir area, located in eastern Texas. Because there are only two LIMIS prototypes currently in existence, their use was prioritized for areas where careful and detailed scrutiny was essential-mainly the low visibility regions of the deeper reservoir and the shallow ponds. According to Wilkins, the LIMIS proved its worth.

"I'm convinced that in the future, the LIMIS will be the replacement system for the PQS-2A, which is now the standard diver hand-held sonar search tool in the U.S. Navy inventory," Wilkins said. "The high resolution heads-up display makes this device the best technological choice for zero-visibility, close-range, underwater searches."

According to Olstad, the LIMIS can be used to quickly scan an object from many different angles to help the diver define its characteristics and exploit it as required. The Limpet Mine Imaging Sonar unit was developed by Dr. Edward O. Belcher at the Applied Physics Laboratory, University of Washington (Seattle) through funding from the Explosive Ordnance-Low Intensity Conflict Program Office. Olstad noted that the LIMIS was able to find objects that most other sensors could not detect at ranges up to 40 feet.

Chief Warrant Officer Jeffrey Barone, one of Mayport, Florida's Shore Intermediate Maintenance Activity's most experienced divers, has used the LIMIS on numerous jobs and has observed that the technology has proven itself many times over.

"There is no other tool in my arsenal that can accomplish the tasking I receive with this high percentage of validity and in as minimal time as the LIMIS can," he commented.

Visibility is exactly what makes this search and recovery so challenging, according to Ron Honaker, a human factors engineer with CSS's Human Systems Integration and Engineering Team. "The Toledo Bend Reservoir is the search site where we used our equipment," Honaker said. It is a body of water that was actually flooded before residential houses and trees could be removed. It was virtually like exploring in an underwater forest."

Despite the tragic circumstances that necessitated the Columbia's debris recovery, CSS's technical experts and MDDS developers were appreciative for the opportunity to evaluate their technology in such an environment. During evaluations at the search site, the LIMIS systems were tested against a variety of search conditions and targets, including actual shuttle pieces placed in the water. After careful review of the LIMIS capabilities, Wilkins designated the LIMIS as the primary visual display sonar asset for searching small areas where larger side-scan sonar units could not be utilized-i.e., in ponds, rivers, and shallow-water areas around piers and seawalls.

CSS personnel participated in a number of actual search operations while at Toedo Bend, including "splash report" areas reported by several eyewitnesses. During these operations, CSS representatives were directly involved in the recovery of five land-based pieces of Columbia debris and their transfer back to the NASA staging site. "Supporting the Columbia in-water recovery operations was a unique and very rewarding opportunity, despite the underlying reason for the search," Honaker said. "But it was an honor and distinct privilege to support the recovery of the Columbia and her crew."

Space shuttle Columbia underwater search and recovery operations are drawing to a close, reports SEA 00C. Though little debris was located in these flooded forests (some recovered material is still being evaluated), Sean O'Keefe, NASA Administrator personally visited dive sites recently to hail this two-month long search by 19 agencies and more than 400 personnel (all under SUPSALV's command and control). He called the effort a major success, by confirming to the maximum extent of technology and human effort that there is no major shuttle debris within the reservoir search areas.

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