obtained: In the first case new time series concepts were developed, and in the 

 second a Fredholm integral equation of the first kind is solved. Both approaches are 

 complimentary in that the strong points of one generally tend to compensate for the 

 weaknesses of the other, and comparisons of final results, where possible, are rein- 

 forcing. 



3.0 INSTRUMENTS 



3.1 Sea Surface Profiler 



The airborne radar wave profiler used in this experiment is an advanced 

 system being developed for the U.S. Naval Oceanographic Office by AMECOM 

 Division of Litton Systems, Inc. It is composed of three functional sections: the 

 antenna assembly, height sensor, and vertical aircraft motion sensor. Figure 1 

 shows a simplified block diagram of the instrument and Table 1 lists its more Impor- 

 tant characteristics o 



The antenna assembly is a single, parabolic reflector using the "Split Feed 

 with Septum" technique which permits the single antenna to function simultaneously as 

 a transmitting antenna on the one half and a receiving antenna on the other. The 

 assembly is mounted very near the center of gravity of the aircraft (a Lockheed Super 

 Constellation). 



Vertical motion of the aircraft is sensed by an accelerometer (range ±lg, 

 sensitivity O.OOOlg), which provides a signal to electronic circuitry where double 

 integration takes place. The output is representative of aircraft displacement and is 

 applied as a second input to a summing network. With proper scaling factor and 

 phasing, this signal cancels the incremental altitude signal input erected by the verti- 

 cal displacement of the aircraft. Ail other signals (wave height information) from the 

 summing network are then forwarded to a precise, fixed gain voltage amplifier, the 

 output of which is recorded on an oscillograph. Figure 2 shows an analog trace of the 

 outputs of the wave height sensor and the doubly integrated accelerometer signal. 



At the operating altitude of 500 feet, the antenna illuminates a circular spot 

 on the sea surface approximately 15 feet in diameter. Theoretically, this places the 

 limit of wave length resolution at 30 feet. In actual practice, however, the system 

 noise level is unacceptable when operating with an instrument response time (.01 

 second) fast enough to match the minimum wave length resolution possible with the 

 antenna. It was decided that the present experiment would concern itself with wave 

 lengths greater than 100 feet, hence, the response time of the system was decreased 

 to 0.1 second. This value effected removal of most of the high frequency noise 

 components in the frequency band of apparent wave intelligence. 



