It is evident that improved service could be obtained if more 

 sources were available and if their angular rates were appreciably 

 higher than sidereal rates. Better coverage would be obtained and 

 the dependence on dead reckoning would be reduced. 



The TRANSIT NAVIGATIONAL SATELLITE SYSTEM, which is 

 now being developed by the U. S. Navy, has these features. Briefly, 

 navigation by a transit satellite is expected to be accomplished in 

 the following manner. Once the satellite is placed in orbit, tracking 

 stations on the surface of the earth will measure the doppler shift of 

 one or more radio signals transmitted by the satellite. From these 

 measurements the future orbit of the satellite can be predicted. 

 Corrected orbital data and accurate time signals will be transmitted 

 from a master computing and injection station to the satellite where 

 they are recorded for rebroadcasting to the mariner. The naviga- 

 tor's receiving equipment will measure the doppler shift of the 

 radio signals transmitted by the satellite for a finite period of time 

 while the satellite is above his radio horizon. From the observed 

 doppler data, the time signals, and orbital information transmitted 

 by the satellite, the navigator can compute his latitude and longi- 

 tude. The frequency of reception of the navigational data will de- 

 pend upon the number of satellites in orbit. It has been stated that 

 four satellites in circular polar orbits would provide fixes every 

 one and one-half hours over most of the earth's surface. Thus, 

 the entire transit system, as presently envisioned, will consist 

 of four orbiting satellites, 10 tracking stations, a master com- 

 puting and injection station, and the shipboard receiving equip- 

 ment. It has been estimated that this system will be operational 

 in 1963 and will be capable of providing worldwide, all-weather 

 fixing information with an accuracy to one-half mile. Present tests 

 utilize complex receiving equipment, including a computer, to 

 realize the full accuracy of the system. However, it is estimated 

 that by 1965, there will be available relatively inexpensive porta- 

 ble shipboard receivers which will provide 1- to 3 -mile accuracy. 

 There are many technical problems in the transit system. 

 However, the potential to the national defense effort for this sys- 

 tem is obvious and its continued development is mandatory. If its 

 technical problems can be resolved, it may provide the ultimate 

 solution to the navigational requirements of the National Oceanog- 

 raphic Program. 



DEAD RECKONING is another of the self-contained systems. 

 By adding course and speed inputs to a previously known position 

 the present position of the vessel can be determined. When 



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