Inclined geosynchronous orbit spacecraft constellations
A constellation of Earth-orbiting spacecraft includes a first spacecraft disposed in a first orbit and a second spacecraft disposed in a second orbit. Each of the first orbit and the second orbit is substantially circular with a radius of approximately 42,164 km. The first orbit and the second orbit have a respective inclination with respect to the equator within a range of 5° to 20°. The first orbit has a first right ascension of ascending node (RAAN1) and the second orbit has a second RAAN (RAAN2) of approximately RAAN1+90°.
1. A constellation of Earth-orbiting spacecraft, the constellation comprising:
a first pair of spacecraft, the pair of spacecraft consisting of a first spacecraft disposed in a first orbit and a second spacecraft disposed in a second orbit, wherein:
the first spacecraft and the second spacecraft are each located at a substantially similar median first longitude and the constellation includes no other spacecraft located at the median first longitude;
each of the first orbit and the second orbit is a substantially circular geosynchronous orbit with a radius of approximately 42,164 km;
the first orbit and the second orbit have a respective inclination with respect to the equator within a range of 5° to 20°; and
the first orbit has a first right ascension of ascending node (RAAN1) and the second orbit has a second right ascension of ascending node (RAAN2) of approximately RAAN1+90°.
2. The constellation of claim 1 , wherein:
the constellation is configured such that the first spacecraft reaches a point of maximum northerly latitude at approximately the same time that the second spacecraft is crossing the equator moving northward.
3. The constellation of claim 1 , wherein the first orbit has a right ascension of ascending node (RAAN) of approximately 315° and the second orbit has a RAAN of approximately 45°.
4. The constellation of claim 1 , wherein each respective spacecraft transmits and/or receives RF signals only during periods of time when that respective spacecraft is at a latitude with magnitude greater than a safe latitude magnitude.
5. The constellation of claim 4 , wherein the safe latitude magnitude is approximately 7.5°.
6. The constellation of claim 4 , wherein the constellation is configured such that, at all times, at least one of the first spacecraft or the second spacecraft is at a latitude with magnitude greater than the safe latitude magnitude.
7. The constellation of claim 4 , wherein the constellation is configured to provide continuous communications services to regions having a latitude between 55° N and 55° S.
8. A method comprising:
executing a stationkeeping strategy for a constellation of Earth-orbiting spacecraft, wherein:
the constellation includes a first pair of spacecraft, the pair of spacecraft consisting of a first spacecraft disposed in a first orbit and a second spacecraft disposed in a second orbit;
the first spacecraft and the second spacecraft are each located at a substantially similar median first longitude and the constellation includes no other spacecraft located at the median first longitude;
each of the first orbit and the second orbit is a substantially circular geosynchronous orbit with a radius of approximately 42,164 km;
the first orbit and the second orbit have a respective inclination with respect to the equator within a range of 5° to 20° ;
a separation between a first right ascension of ascending node (RAAN 1 ) of the first orbit and a second right ascension of ascending node (RAAN 2 ) of the second orbit is approximately 90°; and
the stationkeeping strategy includes maintaining the separation at an approximately constant value of 90° while otherwise allowing RAAN 1 and RAAN 2 to drift.
9. The method of claim 8 , wherein:
the constellation is configured such that the first spacecraft reaches a point of maximum northerly latitude at approximately the same time that the second spacecraft is crossing the equator moving northward.
10. The method of claim 9 , wherein each respective spacecraft transmits and/or receives RF signals only during periods of time when that respective spacecraft is at a latitude with magnitude greater than a safe latitude magnitude.
11. The method of claim 10 , wherein the safe latitude magnitude is approximately 7.5°.
12. The method of claim 10 , wherein the constellation is configured such that, at all times, at least one of the first spacecraft or the second spacecraft is at a latitude with magnitude greater than the safe latitude magnitude.
13. The method of claim 10 , wherein the constellation is configured to provide continuous communications services to regions having a latitude between 55° N and 55° S.
14. A constellation of Earth-orbiting spacecraft, the constellation comprising:
a first plurality of spacecraft disposed in a first orbit and a second plurality of spacecraft disposed in a second orbit, wherein:
each of the first orbit and the second orbit is a substantially circular with a radius of approximately 42,164 km;
the first orbit and the second orbit have a respective inclination with respect to the equator within a range of 5° to 20°;
a first spacecraft of the first plurality of spacecraft and a second spacecraft of the second plurality of spacecraft are each located at a substantially similar first median longitude and the constellation includes no other spacecraft located at the median first longitude; and
the first orbit has a first right ascension of ascending node (RAAN1) and the second orbit has a second RAAN (RAAN2) of approximately RAAN1+90°.
15. The constellation of claim 14 , wherein:
a third spacecraft of the first plurality of spacecraft in the first orbit and a fourth spacecraft of the second plurality of spacecraft disposed in the second orbit are each located at a substantially similar second median longitude that is substantially different from the first median longitude.
16. The constellation of claim 15 , wherein:
a fifth spacecraft of the first plurality of spacecraft in the first orbit and a sixth spacecraft of the second plurality of spacecraft disposed in the second orbit are each located at a substantially similar third median longitude.
17. The constellation of claim 16 , wherein the first median longitude, the second median longitude and the third median longitude are spaced apart by approximately 120°.
18. The constellation of claim 16 , wherein the constellation is configured to provide global continuous communications services to regions having a latitude between 55° N and 55° S.
19. The constellation of claim 14 , wherein the first orbit has a right ascension of ascending node (RAAN) of approximately 315° and the second orbit has a RAAN of approximately 45°.
20. The constellation of claim 14 , wherein each respective spacecraft communicates with the ground only during periods of time when that respective spacecraft is at a latitude with magnitude greater than a safe latitude magnitude.