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The Naval Ocean Systems Center (NOSC) has been tasked by the U.S. Geological Survey to investigate the use of untethered, unmanned submersibles for underwater pipeline and structural inspection. A vehicle of this type is currently under development at NOSC. This robot vehicle, designed as a testbed for free-swimming vehicle technology, is of modular construction and can be expanded to accommodate varying payloads and a variety of sensor systems. The vehicle is 9 ft long, 20 in high, 20 in wide, and weighs approximately 400 lb. It is microprocessor controlled and is capable of following preprogrammed instructions. Programming is accomplished through an umbilical cable which is disconnected after the programming phase. After a time delay the vehicle then performs the preprogrammed operation.

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Inspection of underwater objects such as underwater pipelines and structures can be made more cost-effective if the technology for using unmanned, free-swimming (untethered) submersibles is developed. One major critical area in the development of such vehicle systems is that of a manipulator capability for implacement of sensors, positioning of imaging subsystems, and retrieval of small objects in the water. A small, lightweight, energy-efficient manipulator, which could be operated on an unmanned, free-swimming submersible, was required to act as a testbed for advanced supervisory-control techniques. RESULTS A small, lightweight, electrically driven manipulator capable of handling an 8-pound load in water was designed, developed, and tested in the laboratory. The unit was found to be quite satisfactory as a testbed for advanced supervisory-controlled teleoperator techniques. The oil-filled, pressurecompensated motor assembly design, incorporating potentiometer feedback and harmonic drive gearing, represents one of the most compact underwater designs of its kind in existence. The sleek exterior design, together with the smooth, quiet operation of the entire manipulator configuration, are noteworthy features. RECOMMENDATIONS Advanced techniques in manipulator control should be tested and evaluated with this manipulator mounted on the NOSC/US Geological Survey EAVE WEST freeswimming submersible testbed. CONTENTS

Underwater optical range-gating, designed to extend the maximum range of underwater photography, has been demonstrated in a series of experiments conducted at the NOTS Morris Dam Test Range. With black tape on Scotchlite being used as a target. comparison photographs of gated and non -gated exposures showed promising improvement in the clarity of the gated pictures. This was attributable to the elimination of most of the backscattered light.