Dual LEO satellite system and method for global coverage
The present invention relates to satellite systems and more particularly, to the provision of a satellite system and method for communications applications, with global coverage. An optimal method of providing global broadband connectivity has been discovered which uses two different LEO constellations with inter-satellite links among the satellites in each constellation, and inter-satellite links between the constellations. The first constellation is deployed in a polar LEO orbit with a preferred inclination of 99.5 degrees and a preferred altitude of 1000 km. The second constellation is deployed in an inclined LEO orbit with a preferred inclination of 37.4 degrees and a preferred altitude of 1250 km.
1. A satellite communications system comprising:
a set of satellites in a LEO (low Earth orbit) constellation;
a user terminal for transmitting to, and receiving signals from, said set of satellites; and
a Gateway tear transmitting to, and receiving signals from, said set of satellites;
at least one of said set of satellites being operable to:
transmit and receive signals via a Wide Area Coverage beam;
receive a request from the user terminal for high-capacity beam coverage; and
respond to receiving the request from the user terminal for high-capacity beam coverage by switching the user terminal to a higher bandwidth, narrow, steerable beam, pointed towards the requesting user terminal;
wherein the Gateway is operable to avoid interference with a GEO satellite user terminal by switching the Gateway to an alternate LEO satellite that has an angular separation with a GEO satellite greater than a calculated discrimination angle, as measured at the GEO user terminal.
2. The satellite communications system of claim 1 , wherein each of said set of satellites is further operable to provide broadcast type services.
3. The satellite communications system of claim 1 , wherein each of said set of satellites is further operable to broadcast software distribution to user terminals.
4. The satellite communications system of claim 1 , wherein each of said set of satellites is further operable to broadcast or push Internet content to user terminals.
5. The satellite communications system of claim 1 , wherein the request from a user terminal includes a GPS location which can be used to steer the high bandwidth beam.
6. The satellite communications system of claim 1 , wherein the Gateway is operable to track the satellites across the sky.
7. The satellite communications system of claim 1 , wherein the Gateway and user terminal are operable to handoff communications between the satellites as they move across the sky.
8. A method of operation for a satellite communications system comprising:
launching a set of satellites in a LEO (low Earth orbit) constellation;
using a user terminal, transmitting to and receiving signals from said set of satellites;
using a Gateway, transmitting to and receiving signals from said set of satellites;
at least one of said set of satellites:
transmitting and receiving signals via a Wide Area Coverage beam;
receiving a request from the user terminal for high-capacity beam coverage; and
responding to receiving the request from the user terminal for high-capacity beam coverage by switching the user terminal to a higher bandwidth, narrow, steerable beam, pointed towards the requesting user terminal; and
avoiding interference with a GEO satellite user terminal by switching the Gateway to an alternate LEO satellite that has an angular separation with a GEO satellite greater than a calculated discrimination angle, as measured at the GEO satellite user terminal.