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

Claim 10:
11. A system for determining a range between two unsynchronized communications terminals comprising:
at least one data processor; and
memory comprising instructions which, when executed by the at least one data processor, result in operations comprising:
transmitting, by a first terminal, a range request to a second terminal over a line-of-sight communications channel, wherein the first and second terminals are independently in motion with respect to each other and have unsynchronized timing domains, wherein the terminals are satellites;
storing, by the first terminal, a first timestamp in memory corresponding to a time at which the range request message was transmitted;
receiving, by the first terminal from the second terminal, a range response to the range request, the range response including a residence time that characterizes an amount of time the second terminal required to send the range response after receiving the range request;
storing, by the first terminal, a second timestamp in memory corresponding to a time at which the range response was received;
calculating a roundtrip time for the range request and range response based on the second timestamp minus the first timestamp and the residence time;
calculating a distance between the first terminal and the second terminal based on the roundtrip time;
repeatedly measuring a doppler effect through a periodic sequence of range measurements; and
using the doppler effect measurements to compute a corrected range.