voice transmission. No satisfactory equipment 
currently exists for this underwater acoustic need. 
Development of higher data rates is greatly de- 
sired. 
b. Future Needs Needed will be a long-range 
acoustic communication system requiring investi- 
gations into the feasibility of new types of 
communication links perhaps through the benthic 
layer or solid earth. In the immediate future, an 
acoustic link must be developed to test and 
improve underwater communications and to sup- 
port advancement of other fundamental ocean 
technology. For later developments, it will be 
required as a primary communication link for 
facilities where cable and radio communications 
are not feasible, as in remote locations. = 
Specific developments required for communica- 
tions: 
—High and low frequency sound (infrasound and 
ultrasound) sources and receivers with narrow 
beam and directional characteristics. 
—Acoustic frequency and time conversion meth- 
ods to permit direct usage of a larger portion of 
the acoustic frequency spectrum. 
—Use of refraction layers in the ocean to enhance 
long-range communication and minimize interfer- 
ence from components. 
—Development of acoustic and electronic concepts 
to improve signal-to-noise ratio through signal 
manipulation. 
—Exploitation of other possible communication 
media and such advanced technology as lasers. 
Radio frequency communications among ships, 
buoys, surface platforms, aircraft, satellites, and 
shore stations will require adaptation of equip- 
ment to the special requirements of the ocean 
environment (Figure 9). Problems must be solved 
with respect to allocation of frequencies and 
bandwidths necessary to support ocean activities. 
3. Conclusions 
Navigation is basic to most underwater mis- 
sions. Ocean surveying requires the same types of 
basic reference systems and accuracies as on land. 
Satellite navigation improves accuracy on the 
VL-48 
Figure 9. Communications central aboard 
USC&GSS Oceanographer, one of the most 
completely equipped centrals aboard non- 
military U.S. flag vessels. (ESSA photo) 
ocean surface. However, for surveys below the 
surface, for undersea construction, and for geo- 
logical evaluation, the improved surface accuracy 
may be nullified by the underwater navigation 
method used. 
Undersea exploitation is limited by the lack of 
three-dimensional navigation systems, a combina- 
tion of navigation and bathymetry. The ocean 
environment places severe demands upon subsur- 
face navigation. To the extent that subsurface 
transponders or transmitters exist, accuracy is 
limited by original position determination plus the 
inaccuracies of acoustic ranging and direction- 
fixing. 
Acoustic communications are hampered by 
several basic deficiencies which prevent reliable, 
high speed, wide band, accurate, short and long 
range information exchange. Development of un- 
derwater acoustic link equipment is required for 
habitat-to-surface communications. 
Increasing surface traffic, wider utilization of 
submersibles, and future undersea stations and 
operations will require networks of communica- 
tions-navigation aids. 
Long range acoustic communications are diffi- 
cult to achieve. As alternatives, seismic and earth- 
field communications offer interesting possibil- 
ities. 
