Patent ID: 6243648
Filing Date: 2001-06-05
Classification: G01S

Abstract:
A system for determining a location of a remote terminal located on or near the surface of the Earth by communicating with an orbiting communications satellite, said system comprising:a) a satellite gateway broadcasting an interrogation signal to the remote terminal via the communications satellite;b) said remote terminal including:(i) a receiver receiving the interrogation signal from the communications satellite, said receiver receiving a plurality of signals being broadcast from a plurality of GPS satellites;(ii) a processor measuring at least one characteristic in each of the plurality of signals being broadcast from the plurality of GPS satellites at a first predetermined time relative to receipt of the interrogation signal from the communications satellite; and(iii) a transmitter transmitting a reply signal at a second predetermined time relative to receipt of the interrogation signal to the communications satellite, wherein said reply signal includes the measured characteristic in each of the plurality of signals being broadcast from the plurality of GPS satellites;c) an earth station receiving the reply signal from the communications satellite, and measuring time of arrival information; andd) an operations center calculating a position of the remote terminal using time of arrival information and the measured characteristics returned by the remote terminal.