Abstract: A Low Earth Orbiting satellite system provides location and data communications services to mobile users equipped with a receiver/transmitter. The receiver/transmitter acts as a transponder that responds to a query transmitted over the satellite network. The response is sent after a precisely controlled time interval after the transponder receives the query so that the ground station can estimate the length of the propagation path from the satellite to the transponder. The transponder also transmits the response at a frequency that is proportional to the frequency of the received query so that the ground station can estimate the first and second derivatives of the length of the propagation path according to the measured Doppler shift. The ground station also estimates the satellite positioning using telemetry from the satellite obtained from the on-board GPS receiver. The position of the user terminal relative to the satellite position is then determined from the path length measurements.

Abstract: A Low Earth Orbiting satellite system provides location and data communications services to mobile users equipped with a receiver/transmitter. The receiver/transmitter acts as a transponder that responds to a query transmitted over the satellite network. The response is sent after a precisely controlled time interval after the transponder receives the query so that the ground station can estimate the length of the propagation path from the satellite to the transponder. The transponder also transmits the response at a frequency that is proportional to the frequency of the received query so that the ground station can estimate the first and second derivatives of the length of the propagation path according to the measured Doppler shift. The ground station also estimates the satellite positioning using telemetry from the satellite obtained from the on-board GPS receiver. The position of the user terminal relative to the satellite position is then determined from the path length measurements.

Abstract: A Low Earth Orbiting satellite system provides location and data communications services to mobile users equipped with a receiver/transmitter. The receiver/transmitter acts as a transponder that responds to a query transmitted over the satellite network. The response is sent after a precisely controlled time interval after the transponder receives the query so that the ground station can estimate the length of the propagation path from the satellite to the transponder. The transponder also transmits the response at a frequency that is proportional to the frequency of the received query so that the ground station can estimate the first and second derivatives of the length of the propagation path according to the measured Doppler shift. The ground station also estimates the satellite positioning using telemetry from the satellite obtained from the on-board GPS receiver. The position of the user terminal relative to the satellite position is then determined from the path length measurements.

Abstract: A Low Earth Orbiting satellite system provides location and data communications to mobile users equipped with a receiver/transmitter, which acts as a transponder that responds to a query transmitted over the satellite network. The response is sent after a precisely controlled time interval after the transponder receives the query so that the ground station can estimate the propagation path length. The transponder also transmits the response at a frequency proportional to the frequency of the received query so that the ground station can estimate the first and second derivatives of the propagation path length according to the measured Doppler shift. The ground station also estimates the satellite positioning using satellite telemetry obtained from the on-board GPS receiver. The position of the user terminal relative to the satellite position is then determined from the path length measurements.