centered on 65 kHz with input powers of 5 kW apiece, resulting in a difference frequency of 

 10 kHz with a beamwidlh of 2 deg. With this small a beamwidth, multipath effects were 

 minimized and good video was received. The experiment used amateur radio slow-scan format 

 and Robot Model 400 scan converters to produce the slow-scan signals. 



1.3 RELATION OF SUBSAT TO PREVIOUS WORK 



In view of the past work in acoustic SSTV as outlined above it is important to present 

 the relationship of SUBSAT to these previous experiments. Essentially CUTLINK and the 

 work of Conrad and Moffet showed the initial feasibility of transmitting acoustic SSTV; 

 SUBSAT's aims are to show that these transmissions can be made reliably, cost-effectively 

 and with maximum use of off-the-shelf and already-installed equipment. 



In particular, the unique characteristics of the SUBSAT program are: 



(a) Maximum use of already-installed equipment: The prime application envisioned 

 for SUBSAT is between manned or unmanned submersibles and their surface 

 support craft. Existing craft of this class are more likely than not outfitted with 

 standard UQC (underwater telephone) gear. One of SUBSAT's main objectives 

 is to determine the feasibility of transmitting slow-scan video over such gear 

 without the need for its modification. If successful this would obviously reduce 

 the cost of a slow-scan installation. 



(b) Determination of slow-scan operational envelope: If acoustic slow-scan tele- 

 vision is to be used routinely as an adjunct to UQC communication, the lateral 

 range and depths at which successful transmission is possible need to be made 

 available to the user. SUBSAT's principal goal during FY 78 will be the experi- 

 mental determination of this operational envelope. 



(c) Maximum use of existing scan-conversion technology and standardized SSTV 

 format: Use of scan converters allows the use of fast-scan cameras and moni- 

 tors. In particular the enormous sensitivity of silicon-intensified target cameras 

 can be used to advantage in undersea applications. Scan converters also allow 

 utilization of ordinary closed-circuit monitors, which have good performance 

 under ambient illumination, rather than low-luminosity P7 phosphor cathode 

 ray tubes. By retaining the amateur radio slow-scan format, SUBSAT can use 

 the modern, relatively inexpensive scan converters designed for that market. In 

 particular the Robot 400's full-frame digital memory allows easy interfacing with 

 microprocessors. Software programs have already been designed to do simple 

 processing such as interline interpolation and frame averaging, and work is con- 

 tinuing in this active area. 



2. SUBSAT EXPERIMENTS 



Two SUBSAT experiments were conducted during FY 77. The first, in December 

 1976, which will be referred to as the SEACLIFF experiment, tested acoustic video trans- 

 mission between the submersible SEACLIFF and its surface support ship, MAXINE D. 

 The second was conducted in January 1977 between the USS DOLPHIN and a Box L boat 

 and will be referred to as the DOLPHIN experiment. In both experiments the submerged 



