Method for accurately tracking and communicating with a satellite from a mobile platform

Abstract

A method for accurately tracking and communicating with a satellite from a mobile platform, wherein the satellite has an antenna which performs both transmit and receive functions from a single antenna aperture. The method involves using an inertial reference unit (IRU) of the mobile platform to initially acquire the signal from the satellite. A sequential lobing process is then used to more accurately center the antenna aperture relative to the receive beam from the satellite. The antenna is then used to transmit data or other information, and the antenna pointing is maintained by an additional IRU local to the antenna with higher accuracy and lower latency than the IRU of the mobile platform. Periodically, transmissions from the antenna are inhibited and the sequential lobing process is repeated to eliminate for any inertial reference drift error. The method allows for more accurate antenna pointing when a single antenna aperture is used for both transmit and receive functions without significantly interfering with the transmission of data or information from the antenna.

Description

technical field [0001] The present invention relates to satellite communication systems, and more particularly to a system for use with a mobile platform having an antenna aperture performing receive and transmit functions, and to a system for enabling precise tracking of the antenna aperture as the mobile platform moves method of targeting satellites. technical background [0002] High precision tracking of communication satellites from mobile platforms such as airplanes, ships and land vehicles is required to optimize data rate (ie, peak energy from / to the target) and prevent interference with satellites operating in close proximity to the target satellite. Various tracking methods that have been used include "dead-reckoning" or open-loop methods in which the correct pointing angle is calculated from known satellite and platform positions and platform attitudes. Other methods, such as "closed loop" tracking methods, use some form of feedback control through signal optimiz...

AI Technical Summary

Problems solved by technology

[0006] For antennas where the transmit and receive functions are performed in the same physical antenna aperture, several sources of error are eliminated, but at step sizes where the transmit beam pointing accuracy requirements are smaller than the misalignment used during the timing lobe process , the timing lobe technique cannot be used

Such a situation also results in an error (i.e. misalignment) in the pointing angle of the transmitting antenna relative to the target satellite

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