Apparatus and method for autonavigation with one or more orbiting satellites and an anchor station

A method for carrying out communications between one or more earth-orbiting satellites and a point of fixed position relative to the earth's surface, and for computing the position of said satellites with respect to the earth, comprising the steps of:

• providing an anchor of fixed position relative to the earth's surface;
• broadcasting from each of said satellites an autonomous navigation message, each said message containing said satellite's determination of its own position;
• receiving autonomous navigation broadcasts from each of said satellites at said anchor;
• implementing a tracking algorithm at said anchor for computing a position determination of said orbiting satellites relative to the earth, wherein, said position determination is based on autonomous satellite navigation data and data available independently to said anchor;
• broadcasting said position determinations to said satellites as part of an autonomous navigation message sent from said anchor;
• implementing a tracking algorithm at each of said satellites that is substantially similar to the tracking algorithm implemented at said anchor, said tracking algorithm being used at each of said satellites to generate an updated satellite position determination;
• and
• broadcasting said updated satellite position determinations for reception by said anchor and said satellites.

A system for carrying out communications between one or more earth-orbiting satellites and a point of fixed position relative to the earth's surface, and for computing the position of said satellites with respect to the earth, comprising:

• transmitting means on board each of said satellites for transmitting data to said anchor and for transmitting data to other of said satellites;
• an anchor having an anchor receiving means for receiving data from said satellites, a first processing means for computing a position determination for each of said satellites, and for computing a satellite clock time, a means for computing a corrected clock value by comparing said satellite clock time to a time reference, and an anchor transmitting means for transmitting said position determination and said corrected clock value to said satellites, said position determination being updated every time a transmission is received from one of said satellites;
• receiving means on board each of said satellites for receiving transmissions from said anchor and for receiving transmissions from other of said satellites;
• and
• means on board each of said satellites for extracting position and time data received from said anchor and from other satellites, and for using said position and time data as input to a second processing means, said second processing means computing an on-board position determination for each of said satellites and for computing an on-board corrected clock value.