NZ743631B2

NZ743631B2 - Satellite system and method for global coverage

Info

Publication number: NZ743631B2
Application number: NZ743631A
Authority: NZ
Inventors: Andre E Bigras; Peter Megyeri; Paul Ng; Jack Rigley; Alireza Shoamanesh; Surinder Singh
Original assignee: Telesat Canada
Filing date: 2016-11-25
Publication date: 2024-09-03

Abstract

The present invention relates to satellite systems and more particularly, to the provision of a novel, non-geostationary satellite system and method for weather and climate monitoring, communications applications, scientific research and similar tasks, with global coverage. Contrary to the teachings in the art it has been discovered that global coverage may be obtained using a constellation of six satellites in two orthogonal, 24 sidereal hour orbits (geosynchronous) with inclinations of 70° to 90°, and eccentricities of 0.275 - 0.45. By placing three of the satellites in a first orbit with an apogee over the north pole, and three of the satellites in a second, orthogonal orbit with an apogee over the south pole, global coverage may be obtained. As well, the satellites in these orbits avoid most of the Van Allen Belts.

Claims

WHAT IS CLAIMED IS:

1. A satellite system for global coverage comprising: a constellation of six satellites, three of said satellites orbiting in a first orbit and the other three of said satellites orbiting in a second orbit; the first orbit having an orbital inclination approximately between 70° and 90°, an apogee over the northern hemisphere, a perigee which avoids an inner Van Allen belt of high energy protons, and an orbital eccentricity of greater than 0.28 and less than 0.45; the second orbit having an orbital inclination approximately between 70° and 90°, an apogee over the southern hemisphere, a perigee which avoids the inner Van Allen belt of high energy protons, and an orbital eccentricity of greater than 0.28 and less than 0.45; a major axis of the first orbit being substantially aligned with a major axis of the second orbit, and planes of the first orbit and the second orbit being orthogonal to one another; and at least one base station being configured to transmit to, and receive signals from said constellation of six satellites.

2. The system of claim 1 wherein the orbital eccentricity and the orbital inclination of each of the first and second orbits are selected to provide 99% global coverage, with an elevation angle of at least 10°.

3. The system of either one of claims 1 and 2, wherein the orbital inclination of each of the first and second is approximately between 80° and 90°.

4. The system of any one of claims 1 to 3, wherein the orbital inclination of each of the first and second orbits is approximately 90°.

5. The system of any one of claims 1 to 4, wherein the orbital eccentricity and the orbital inclination of each of the first and second orbits are selected to provide continuous global coverage, with an elevation angle of at least 8.7°.

6. The system of any one of claims 1 to 5, wherein the orbital eccentricity of each of the first and second orbits is approximately between 0.30 and 0.34. -3 3 -

7. The system of any one of claims 1 to 6, wherein the satellites have an orbital period of one sidereal day.

8. The system of any one of claims 1 to 7, wherein phasing of the satellites is such that a time between their respective apogees is approximately an orbital period divided by a number of satellites in the orbit.

9. The system of any one of claims 1 to 8, wherein directional antennas are used for communications between the satellites and the base station.

10. The system of any one of claims 1 to 9, wherein the orbital eccentricity and the orbital inclination of each of the first and second orbits are selected to result in a 50 krad radiation exposure over 15 years, allowing the use of conventional GEO satellite shielding.

11. A method of operation for a satellite system satellite system for Earth observation and communications having global coverage, comprising: providing a constellation of six satellites, three of said satellites orbiting in a first orbit and the other three of said satellites orbiting in a second orbit; the first orbit having an orbital inclination approximately between 70° and 90°, an apogee over the northern hemisphere, a perigee which avoids the inner Van Allen belt of high energy protons, and an orbital eccentricity of greater than 0.28 and less than 0.45; the second orbit having an orbital inclination approximately between 70° and 90°, an apogee over the southern hemisphere, a perigee which avoids the inner Van Allen belt of high energy protons, and an orbital eccentricity of greater than 0.28 and less than 0.45; a major axis of the first orbit being substantially aligned with a major axis of the second orbit, and planes of the first orbit and the second orbit being orthogonal to one another; and providing at least one base station for transmitting to and receiving signals from said constellation of six satellites. -3 4 -

12. The method of claim 11, wherein the orbital inclination of each of the first and second orbits is approximately between 80° and 90°.

13. The method of either one of claims 11 and 12, wherein the orbital eccentricity of each of the first and second orbits is approximately between 0.30 and 0.34.

14. The method of any one of claims 11 to 13, wherein the satellites have an orbital period of one sidereal day.

15. The method of any one of claims 11 to 14, wherein phasing of the satellites is such that the time between their respective apogees is approximately an orbital period divided by a number of satellites in the orbit.

16. A satellite base station, comprising: a communication system for transmitting and receiving signals to and from a constellation of six satellites, said constellation of six satellites providing global coverage; and a flight control system for controlling said constellation of six satellites such that: three of said satellites orbit in a first orbit and the other three of said satellites orbit in a second orbit; the first orbit having an orbital inclination approximately between 70° and 90° with respect to a first pole of the Earth, an orbital eccentricity of greater than 0.275 and less than 0.45, and a perigee which avoids an inner Van Allen belt of high energy protons; the second orbit having an orbital inclination approximately between 70° and 90° with respect to a second pole of the Earth, and an orbital eccentricity of greater than 0.275 and less than 0.45, and a perigee which avoids an inner Van Allen belt of high energy protons; and a major axis of the first orbit being substantially aligned with a major axis of the second orbit, and planes of the first orbit and the second orbit being substantially orthogonal to one another.

17. The satellite base station of claim 16, wherein the orbital inclination of each of the first and second orbits is approximately between 80° and 90°. -3 5 -

18. The satellite base station of either one of claims 16 and 17, wherein the orbital eccentricity of each of the first and second orbits is approximately between 0.30 and 0.34.

19. The satellite base station of any one of claims 16 to 18, wherein each of the satellites has an orbital period of one sidereal day.

20. The satellite base station of any one of claims 16 to 19, wherein phasing of the satellites is such that the time between their respective apogees is approximately an orbital period divided by a number of satellites in the orbit. -3 6 - 6 SATELLITES GLOBAL COVERAGE VS. ORBIT INCLINATION GLOBAL AREA COVERAGE 100.00% 95.00% 90.00% 85.00% 80.00% 75.00% 70.00% 90 80 70 60 50 40 30 20 10 0 INCLINATION (DEG)