Sponsoring Agency Code
Supplementary Notes
AbstractPosition surveillance using one active ranging/communication satellite and the time-of-arr i val of signals from an independent satellite was shown to be feasible and practical.A towboat on the Mississippi River was equipped with a tone-code ranging transponder and a receiver tuned to the timing signals of the GOES satellite. A similar transponder was located at the office of the towing company..Tone-code ranging interrogations were transmitted from the General Electric Earth Station Laboratory through ATS-6 to the towboat and to the "ground truth" transponder office. Their automatic responses included digital transmissions of t ime-of-arr i val measurements derived from the GOES signals.The Earth Station Laboratory determined ranges : ' ; '"' from the satellites to the towboat and computed position fixes. The ATS-6 1 ines-ofposition were more precise than 0.1 NMi, la, and the GOES 1 ines-of-posi t ion were more precise than 1.6 NMi, la.High quality voice communications were accomplished with the transponders using a sma 1 non-directional antenna on the towboat. The position fixing technique offers the advantages of surveillance, worldwide and continuously available, as an adjunct to satellite communications. The vehicle equipment that must be added for the surveillance function is likely to be lower in cost than equipment used with existing and planned radio and satellite navigation systems. The cost of position fixes in an operational system would be a trivial addition to the communication costs because the duration of the interrogation-response messages is short, as is the computer time for a fix determination. There are no space segment costs beyond those of the communication satellites, and the cost of ground station facilities are insignificant compared to those of any existing or planned radio or satellite navigation systems.The potential advantages of the surveillance technique justify its further evaluation for operational implementation in comparison with other approaches that are under consideration in national plans for navigation.
