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Geolocation Communications Method During Visibility Between an Earth-Orbit Satellite and a Transmitter and Receiver

Abstract: 

A method for determining the geolocation of an object such as a vehicle traversing the earth's surface or airborne thereabove
includes employing a device which is capable of operating autonomously to transmit signals to a selected low earth orbit (LEO)
satellite for relay to a receiving station whose position is known, identifying the device and its geolocation, speed, altitude and/or
heading. The device includes a microcomputer which operates a Global Positioning System (GPS) receiver for receiving GPS
signals to identify the device geolocation and the precise time. A nonvolatile memory on board the device stores LEO satellite
ephemeris data, satellite operational and message formatting parameters, LEO satellite visibility footprint data and visibility
contour information for the device caused by obstacles which are permanently or temporarily in proximity to the device during
deployment and which block transmission of signals between the device and the LEO satellite, depending on relative positions.
Geolocation information is transmitted to a LEO satellite for relay to the receiving station after calculation of covisibility of the
satellite with the receiving station and the transmitter antenna for the device, taking into account the device visibility contour and
heading. The device transmitter antenna may have a steering mechanism for causing the antenna to be aimed at a predetermined
azimuth and elevation wherein the transmitted signals will be intercepted by the LEO satellite.

Patent Number: 
6,157,896
Date Of Issue: 
12/05/2000
Inventors: 

M. Pike Castles;Austin Walker Boyd, Jr.; James Andrew Moryl