| 摘要 |
<p>A satellite position determination system, for use in a communications environment, has an earth station (11) generate a positional signal which is relayed by the satellite (10) to all user terminals (13) within the coverage (16) of the satellite by using a single global beam (108), simultaneously generated on the same phased antenna array (42, 44) otherwise used to generate spot beams (30) for satellite communications. The earth station (11) also comprises a system for correcting the positional signal, which consists in time of satellite emission and contemporary satellite position, by monitoring the global beam, noting any errors in delay between satellite (10) and the earth station (11), and adjusting the time signal in the positional signal to correct the error. There is also provided an iterative method for correcting the internal clock in the user terminal (13) whereby drift is compensated and the correct time established, resulting in ever better positional estimates for the user terminal (13).</p> |
