Patent ID: 11902016
Assignee: THE MITRE CORPORATION
Field: Telecommunications (Electrical engineering)
Classification: CPC H | IPC H

Claim 17:
18. A system comprising:
a first communications terminal in communication with
a second communications terminal over a line-of-sight communications channel, wherein the first and second communications terminals are independently in motion with respect to each other and have unsynchronized timing domains, and the terminals are satellites;
wherein the first communications terminal:
transmits a range request to the second terminal;
stores a first timestamp in memory corresponding to a time at which the range request message was transmitted;
receives, from the second communications terminal, a range response to the range request, the range response including a residence time that characterizes an amount of time the second communications terminal required to send the range response after receiving the range request;
stores a second timestamp in memory corresponding to a time at which the range response was received;
calculates a roundtrip time for the range request and range response based on the second timestamp minus the first timestamp and the residence time; and
calculates a distance between the first communications terminal and the second communications terminal based on the roundtrip time;
repeatedly measures a doppler effect through a periodic sequence of range measurements; and
uses the doppler effect measurements to compute a corrected range.