Method and apparatus for selectively operating satellites in tundra orbits

Abstract

A satellite system provides geosynchronous satellites in elliptical orbits in respective elliptical orbital planes separated by 120 degrees. The satellites traverse a common figure-eight ground track comprising northern and southern loops. The satellites are controllably switched to operate the satellite currently traversing the northern loop to deliver a selected signal (e.g., a selected frequency signal) to satellite receivers.

1 . A method for controlling first and second geosynchronous satellites in elliptical orbits in respective orbital planes in a satellite communication system, the satellite communication system providing at least one of a first frequency signal and a second frequency signal to receivers, the satellites each traversing a common ground track having a northern loop, a southern loop, and a crossover point between the northern and southern loops, the method comprising the steps of:
 selecting said first frequency satellite signal to be transmitted from whichever of said first and second geosynchronous satellites is approaching and traversing said northern loop;   monitoring the orbital positions of said first and second geosynchronous satellites with respect to entering said northern loop and exiting said northern loop;   switching via a satellite command system said first frequency signal to one of said first and second geosynchronous satellites as said satellite approaches said northern loop;   powering down said first and second geosynchronous satellites when they are descending said southern loop below the equator; and   powering on said first and second geosynchronous satellites when they are ascending said southern loop from the equator.   
     
     
         2 . A method as claimed in  claim 1 , further comprising the step of transmitting said second frequency satellite signal from a third geosynchronous satellite.