CW beacon system for hydrophone motion determination

Abstract

A system consisting of three bott0m-moored 12 000-Hz CW beacons, each separated in frequency by 40 Hz, and separated in space by about 8 k.m, has been used to track the motion of ship-suspended, ship-mounted, sonobuoy-deployed, and bottom-moored hydrophones to an accuracy of 4 cm. The system uses Doppler tracking of the beacon signals to provide real-time estimation of hydrophone velocity and displacement. Factors that m'•,ht compromise system performance, such as surface, bottom or forward volume scattering, ot multipath effects, were found to be negligible. Random phase fluctuations in beacon signals due to these phenomena are small compared with those due to hydrophone motion. Two tests of the system, near Eleuthera Island and near Bermuda, were made in September-October 1972. [This work was performed under U.S. Office of Naval Research Contract No. N00014-72-C-0205.].

Analysis of a high resolution deep ocean acoustic navigation system

“…Random phase fluctuations can be caused by multipath interference and forward scattering. The root mean square phase fluctuations from these sources has been estimated to be about .13 quadrants (Porter et al ( 1973). When compared with the errors due to ambient sea noise shown in Table 2 they have little effect (about 5-15% increase in Get ) and can be considered negligible.…”

“…continuous wave (CW) beacon system has been developed at the Woods Hole Oceanographic Institution to accurately track the position of ship-mounted and submerged hydrophones (Porter et al_. , 1973 profile, the depths of the transponder, and the survey point and varies with the amount of acoustic refraction (Vass, 1966) .…”

“…Travel times are computed using standard ray acoustic techniques (Officer, 1958 .»-« where f is the sampling frequency of the phase detector outputs (10 Hz) (Porter et al , 1973). where Pe is the probability of error in the n sample.…”

Inverse methods and results from the 1981 Ocean Acoustic Tomography Experiment

“…The problem of mooring motion was solved by using a refined version of the mooring tracking system developed at Woods Hole Oceanographic Instition by Spindel, Porter, and Jaffee (1973). The system uses three transponders installed on the ocean bottom in a triangle surrounding the mooring, which are interrogated by another transponder on the mooring.…”

“…Porter, Spindel, and Jaffee (1973) developed a mooring tracking system which used the travel times of acoustic transmissions to monitor the motion of a mooring. By 1977, low-frequency sound transmissions were being used to track neutrally bouyant "SOFAR" floats over long distances (Webb (1977), Spindel, Porter, and Webb (1977), or see Baker (1981)).…”