In some instances, two or more simultaneous television channels may be desirable, 

 perhaps to achieve a visual stereo effect, and thus the bandv/idth requirement of the trans- 

 mission channel will be increased. Real-time TV probably has the highest bandwidth require- 

 ment of any sensor hkely to be employed with an undersea inspection vehicle, and as such 

 will drive the system bandwidth requirement. 



Sonar is often employed as a sensor on undersea vehicles to extend the viewing range 

 greatly over that obtainable by using television, but with a corresponding reduction in reso- 

 lution. Both front-looking and side-looking units have been employed. Such sonars require 

 channel bandwidth that range from perhaps 10 kHz to more than 500 kHz, depending on 

 capability. The dynamic range required is on the order of 20 to 30 dB. 



Such sensors as magnetometers and fluorometers undoubtedly will be desirable on 

 some vehicles, especially those used for pipeline inspection. Data from these low-bandwidth 

 sensors is best transmitted digitally, with expected data rate requirements of only a few bits 

 per second. This class of sensor information is best transmitted by allowing the microproces- 

 sor controller to incorporate it, along with such data as compass heading and depth, via the 

 UART command-control link. 



Akin to sensors are manipulators, which range from simple claws to sophisticated 

 tactile, force-feedback units. It is possible that the inspection vehicle will contain some 

 form of manipulator which will allow it to attach markers and hnes to points of interest. 

 A supervisory-controlled manipulator soon will be installed on the EAVE WEST submersible 

 as one of the other technologies that are being investigated as part of the EAVE Program 

 (ref 5 and 6). Manipulators can, like low-rate sensors, be accommodated via the UART link, 

 although the more complex units will probably require the 9600-baud rate to minimize time 

 lag in the control loop. 



In the fiber-optically coupled free swimmer, therefore, it is obvious that the com- 

 munications link must be duplex; this can be realized by the use of different wavelengths or 

 light for the uplink and downlink signals. The downUnk will be digital PCM (pulse code 

 modulation) via a UART operating at 9600 baud to maximize the data transfer rate and pro- 

 vide for manipulator control. The uplink will carry an identical UART channel as well as a 

 monochrome television channel requiring a bandwidth of approximately 4 MHz. The 

 UART channel can be readily time-division-multiplexed into the blanking interval of the 

 television channel. In addition, missions may require color and/or stereo television sensors, 

 which will increase the bandwidth even more. Finally, a sonar channel having a bandwidth 

 requirement which is a small fraction of that required for television may be mandated if 

 visibility range in excess of that obtainable with optical techniques is required. 



3.0 SYSTEM REALIZATION 



We will now attempt to address the specific areas of investigation which are required 

 to develop a total system suitable for use on the EAVE WEST submersible for OCS pipeline 

 and structures inspection. In each of these areas, it was necessary to make choices that best 

 suited the OCS inspection appHcation (which may not necessarily be the same choice desira- 

 ble for military apphcations). For example, the desire to investigate the use of an unarmored 

 fiber link, which would be a low-cost, throwaway item, was important to the OCS scenario, 

 in which the operational cost for inspections is important. On the other hand, such items as 

 spool fabrication techniques and modulation and multiplexing techniques obviously have a 

 wide area of application for all types of underwater operations. 



15 



