for the Navy Bureau of Weapons . Three of these are presently in orbit and have 

 been operational since July 1964. Over this period some operational units of the 

 fleet have made extensive use of Transit in all parts of the world and have 

 reported navigational fixes accurate to ±0.1 nautical mile. Transit is designed 

 to provide this accuracy on an all-weather, 24 -hour -a -day routine basis . 



Westinghouse is responsible for the integration of the antenna, the 

 data processor, the computer, and the new special -purpose receiver to form the 

 "Navigational Shipboard Receiver" (AN/BRN-3). This receiver provides four 

 basic outputs required for the navigation solution: 



(1) Vacuum Doppler frequency (corrected for refraction) 



(2) Digital data that furnish the navigator with satellite 

 orbital information 



(3) Timing pulses that provide accurate time information 



(4) Imc reference and clock frequency, which through a 

 frequency synthesizer provides all of the system conr 

 version and reference frequencies . 



The present Transit receiving and computing system requires several 

 racks of equipment(^) which, because of size and power requirement, is proba- 

 bly unsuitable for most aircraft use. Certain simplifications have been sug- 

 gested(4) which will decrease receiving equipment size and power requirements 

 as well as initial cost, while decreasing the fix accuracy only a modest amount. 



4 . NONMILITARY SATELLITE NAVIGATION 



Because of probable economic requirements , the nonmilitary satellite 

 systems being studied will require only a minimum amount of equipment aboard 

 the navigating vessel . The bulk of the complex and expensive computer equip - 

 ment will be concentrated at properly positioned shore stations . For these sys - 

 tems the navigator would not need to be concerned with satellite orbit informa- 

 tion and the corrections required for accurate computations . An additional 

 advantage of the "cooperative" systems is that they permit traffic control, navi- 

 gation hazard warning, and aids to vessels in distress; these are made possible 

 by the positional information control available at the computer station. 



Each vessel navigating in a given area would be assigned time slots 

 for satellite transmission, the frequency of which would depend upon the vessel's 

 requirements for position information. The satellite would be automatically 

 interrogated by the ground station and navigating vessel. The satellite thus 

 would serve as a retransmitting station to relay all measurement information to 

 a ground station for computation and then relay the resulting positional informa- 

 tion back to the vessel. In this manner one line of position could be established 



91 



Arthur ZD.ItittlcIlnr. 



