Hybrid RF/optical communications with RF system that provides continuous service during downtime in optical handoff

1. A computer-implemented method, comprising:

establishing an optical communication link between an optical communication system of a first balloon and an optical communication system of a second balloon;

detecting a rotation of the second balloon about an axis of the second balloon;

determining that of the rotation about the axis of the second balloon is predicted to cause the optical communication link to become unavailable at a given future time during the rotation, wherein the optical communication link is predicted to remain unavailable until the rotation is such that the optical communication link can be re-established between the optical communication system of the first balloon and the optical communication system of the second balloon;

in response to determining that the rotation of the second balloon about the axis of the second balloon is predicted to cause the optical communication link to become unavailable at the given future time during the rotation, establishing a radio frequency (RF) communication link between an RF communication system of the first balloon and an RF communication system of the second balloon before the given future time;

after establishing the RF communication link, detecting that the rotation of the second balloon about the axis is such that the optical communication link between the optical communication system of the first balloon and the optical communication system of the second balloon can be re-established; and

re-establishing the optical communication link based on the determined rotation between the optical communication system of the first balloon and the optical communication system of the second balloon.

2. The method of claim 1 , wherein establishing the optical communications link between the optical communication system of the first balloon and the optical communication system of the second balloon comprises aligning a directional transceiver of the first balloon with a directional transceiver of the second balloon.

3. The method of claim 1 , wherein:

the optical communication system of the first balloon comprises a plurality of directional transceivers;

the optical communication link is established using a first directional transceiver of the optical communication system of the first balloon;

the optical communication link is re-established using a second directional transceiver of the optical communication system of the first balloon.

4. The method of claim 1 , further comprising:

determining a level of atmospheric interference that is expected to cause the optical communication link between the optical communication system of the first balloon and the optical communication system of the second balloon to become unavailable for a given time period;

before the optical communication link becomes unavailable, establishing an RF communication link between the RF communication system of the first balloon and the RF communication system of the second balloon;

after establishing the RF communication link, detecting that the level of atmospheric interference is such that the optical communication link between the optical communication system of the first balloon and the optical communication system of the second balloon can be re-established; and

re-establishing the optical communication link based on the detected level of atmospheric interference between the optical communication system of the first balloon and the optical communication system of the second balloon.

5. The method of claim 1 , further comprising:

establishing an RF communication link between the RF communication system of the first balloon and an RF communication system of a third balloon;

after establishing the RF communication link between the RF communication system of the first balloon and the RF communication system of the third balloon, detecting a movement of the third balloon relative to the first balloon such that an optical communication link between the optical communication system of the first balloon and an optical communication system of the third balloon can be established; and

establishing the optical communication link between the optical communication system of the first balloon and the optical communication system of the third balloon.

6. The method of claim 5 , wherein establishing the optical communication link between the optical communication system of the first balloon and the optical communication system of the third balloon comprises discontinuing the optical communication link between the optical communication system of the first balloon and the optical communication system of the second balloon by redirecting a directional transceiver of the first balloon from a directional transceiver of the second balloon to a directional transceiver of the third balloon.

7. The method of claim 1 , wherein determining that the rotation is predicted to cause the optical communication link to become unavailable at the given future time during the rotation comprises determining that a component of the first balloon or the second balloon is predicted to block a path between respective directional transceivers on the first balloon and the second balloon at the given future time.

8. The method of claim 7 , wherein the component comprises a payload of the first balloon or the second balloon.

9. The method of claim 1 , further comprising determining a current speed of rotation of the second balloon, wherein determining that the rotation is predicted to cause the optical communication link to become unavailable at the given future time during the rotation is based on the current speed of rotation of the second balloon.

10. The method of claim 1 , wherein establishing the RF communication link between the RF communication system of the first balloon and the RF communication system of the second balloon before the given future time comprises establishing the RF communication link with a chosen time buffer before the given future time.

11. A balloon, comprising:

an RF communication system;

an optical communication system; and

a control system configured to:

establish an optical communication link between the optical communication system of the balloon and an optical communication system of a second balloon;

detect a rotation of the second balloon about an axis of the second balloon;

determine that the rotation about the axis of the second balloon is predicted to cause the optical communication link to become unavailable at a given future time during the rotation, wherein the optical communication link is predicted to remain unavailable until the rotation is such that the optical communication link can be re-established between the optical communication system of the balloon and the optical communication system of the second balloon;

in response to determining that the rotation of the second balloon about the axis of the second balloon is predicted to cause the optical communication link to become unavailable at the given future time during the rotation, establish an RF communication link between the RF communication system of the balloon and an RF communication system of the second balloon;

after establishing the RF communication link, detect that the rotation of the second balloon about the axis is such that the optical communication link between the optical communication system of the balloon and the optical communication system of the second balloon can be re-established; and

re-establish the optical communication link based on the determined rotation between the optical communication system of the balloon and the optical communication system of the second balloon.

12. The balloon of claim 11 , wherein:

the optical communication system of the balloon comprises a plurality of directional transceivers; and

the control system is configured to:

establish the optical communication link using a first directional transceiver of the optical communication system of the balloon; and

re-establish the optical communication link using a second directional transceiver of the optical communication system of the balloon.

13. The balloon of claim 11 , wherein the control system is further configured to:

determine a level of atmospheric interference that is expected to cause the optical communication link between the optical communication system of the balloon and the optical communication system of the second balloon to become unavailable for a given time period;

before the optical communication link becomes unavailable, establish an RF communication link between the RF communication system of the balloon and the RF communication system of the second balloon;

after establishing the RF communication link, detect that the level of atmospheric interference is such that the optical communication link between the optical communication system of the balloon and the optical communication system of the second balloon can be re-established; and

Re-establish the optical communication link based on the detected level of atmospheric interference between the optical communication system of the balloon and the optical communication system of the second balloon.

14. The balloon of claim 11 , wherein the control system is further configured to:

establish an RF communication link between the RF communication system of the balloon and an RF communication system of a third balloon;

after establishing the RF communication link between the RF communication system of the balloon and the RF communication system of a third balloon, detect that a movement of the third balloon relative to the balloon is such that an optical communication link between the optical communication system of the balloon and an optical communication system of the third balloon can be established; and

establish the optical communication link between the optical communication system of the balloon and the optical communication system of the third balloon.

15. A method, comprising:

establishing an optical communication link between an optical communication system of a ground-based station and an optical communication system of a balloon;

detecting a rotation of the balloon about an axis of the balloon;

determining that the rotation about the axis of the balloon is predicted to cause the optical communication link to become unavailable at a given future time during the rotation, wherein the optical communication link is predicted to remain unavailable until the rotation is such that the optical communication link can be re-established between the optical communication system of the ground-based station and the optical communication system of the balloon;

in response to determining that the rotation of the balloon about the axis of the balloon is predicted to cause the optical communication link to become unavailable at the given future time during the rotation, establishing an RF communication link between an RF communication system of the ground-based station and an RF communication system of the balloon before the given future time;

after establishing the RF communication link, detecting that the rotation of the balloon about the axis is such that the optical communication link between the optical communication system of the ground-based station and the optical communication system of the balloon can be re-established; and

re-establishing the optical communication link based on the determined rotation between the optical communication system of the ground-based station and the optical communication system of the balloon.

16. The method of claim 15 , wherein:

the optical communication system of the ground-based station comprises a plurality of directional transceivers;

the optical communication link is established using a first directional transceiver of the optical communication system of the ground-based station;

the optical communication link is re-established using a second directional transceiver of the optical communication system of the ground-based station.

17. The method of claim 15 , further comprising:

determining a level of atmospheric interference that is expected to cause the optical communication link between the optical communication system of the ground-based station and the optical communication system of the balloon to become unavailable for a given time period;

before the optical communication link becomes unavailable, establishing an RF communication link between the RF communication system of the ground-based station and the RF communication system of the balloon;

after establishing the RF communication link, detecting that the level of atmospheric interference is such that the optical communication link between the optical communication system of the ground-based station and the optical communication system of the balloon can be re-established; and

re-establishing the optical communication link based on the detected level of atmospheric interference between the optical communication system of the ground-based station and the optical communication system of the balloon.

18. The method of claim 15 , further comprising:

establishing an RF communication link between the RF communication system of the ground-based station and an RF communication system of a second balloon;

after establishing the RF communication link between the RF communication system of the ground-based station and the RF communication system of a second balloon, detecting a movement of the second balloon relative to the ground-based station such that an optical communication link between the optical communication system of the ground-based station and an optical communication system of the second balloon can be established; and

establishing the optical communication link based on the detected movement between the optical communication system of the ground-based station and the optical communication system of the second balloon.

19. A non-transitory computer readable medium having stored therein instructions, that when executed by a computing system, cause the computing system to perform functions comprising:

establishing an optical communication link between an optical communication system of a first balloon and an optical communication system of a second balloon;

detecting a rotation of the second balloon about an axis of the first balloon;

determining that the rotation about the axis of the second balloon is predicted to cause the optical communication link to become unavailable at a given future time during the rotation, wherein the optical communication link is predicted to remain unavailable until the rotation is such that the optical communication link can be re-established between the optical communication system of the first balloon and the optical communication system of the second balloon;

in response to determining that the rotation of the second balloon about the axis of the second balloon is predicted to cause the optical communication link to become unavailable at the given future time during the rotation, establishing a radio frequency (RF) communication link between an RF communication system of the first balloon and an RF communication system of the second balloon before the given future time;

after establishing the RF communication link, detecting that the rotation of the first balloon about the axis is such that the optical communication link between the optical communication system of the first balloon and the optical communication system of the second balloon can be re-established; and

re-establishing the optical communication link based on the determined rotation between the optical communication system of the first balloon and the optical communication system of the second balloon.