274 



ANNUAL REPORT SMITHSONIAN INSTITUTION, 1960 





^M^!»Mu.^^wiiA^ 









Figure 4. — This preliminary radar map of the moon is from 440-megacycle observations 

 with the 84-foot Millstone Hill antenna on January 8, 1960, at 0:04 Universal time 

 The sharp semicircular boundary corresponds to the moon's edge seen from above (as in 

 III of fig. 3), the part of the moon nearest the earth being at the top of the map. The 

 range increases downward by steps of 0.0005 second of radar echo time per line. Since 

 the echoes from the center of the moon as we see it are enormously stronger than the 

 limb echoes (bottom), the signaLstrengths have been scaled down by the factors labeled 

 at the left. 



noise receivers, and signal-processing techniques. The average power 

 available at frequencies extending from 30 megac^^cles per second to 

 30,000 megacycles must be increased. In many cases, the radio power 

 available at present is already crowding the capacity of a single trans- 

 mission line. New methods are needed to generate and distribute the 

 power over the antenna surface without having to funnel it all through 

 one transmission line. In order to preserve complete knowledge of the 

 transmitted waveform, these new transmitters must not distort the 

 output, even at the highest frequencies and powers that may be used. 

 Perhaps the most important field for improvement is antenna capa- 

 bility. In radar systems, the antenna plays a dual role, contributing 

 to the outgoing "power-on-target," and also determining the amount 

 of scattered signal that may be gathered into the receiver. At the 

 present time, antenna designs so nearly achieve full theoretical effi- 

 ciency, for a given size and operating frequency, that little remains 

 but to increase the collecting area if more sensitivity is to be realized. 

 Certainly the current trend lies in that direction. An example of the 



