This report describes the Evaluation Measurement System and associated depth-keeping 

 servo system, briefly explains the principles of operation and describes the hardware. The 

 report also includes a description of the measurement system permanently installed aboard 

 the submarine required for BIAS buoy operation. 



GENERAL CONSIDERATIONS 



One of the requirements for development of the BIAS buoy communication system was 

 the design and fabrication of an instrumentation system to measure certain buoy and tow- 

 cable parameters while under tow. Measurement of these parameters would serve four pur- 

 poses: ( 1) to provide basic quantitative hydromechanic evaluation of buoy design during 

 experiments in the towing basins of the Center and at sea, (2) to confirm predicted towcable 

 configurations at sea, (3) to provide the submarine operating crew with the necessary data for 

 buoy-positioning winch operation, and'(4) to provide warning of malfunctions in order that 

 corrective action may be taken to assure submarine safety. 



In addition to the above requirement, an automatic buoy depth-keeping system was 

 highly desirable. This system would operate in two automatic modes: (1) to cause the buoy 

 to follow 4 feet below the water surface (a requirement for high-frequency radio transmission 

 and reception) and (2) to cause the buoy to operate at a nominal 20 feet deep (for VLF 

 reception only). 



The hydromechanics evaluation of a cable-buoy system requires the measurement of the 

 nine parameters listed in Table 1 to provide the data necessary for validation of the steady- 

 state cable configurations. The general towing configuration and the location of the various 

 sensors are depicted in Figure 1 . The signals from the buoy sensors are telemetered down 

 one conductor of the towcable for recording at the data center. A remotely controlled and 

 automatic sequencing switch network is incorporated within the buoy instrument housing to 

 zero reference and electrically calibrate the sensors which may be used to eliminate measure- 

 ment errors due to long-term sensitivity and zero shifts of the data transmitting and recording 

 electronics. The sensors at the submarine end of the towcable are direct-wired to the data 

 center for recording. 



PRINCIPLES OF OPERATION 



The following discussion deals with the general operating principles of the Buoy Evalua- 

 tion Measurement System (which includes an Automatic Buoy Depth-Keeping System) and a 

 Buoy Operational Measurement System for use by the submarine crew while on patrol. 



