Systems and methods for high-altitude radio/optical hybrid platform

1. A geostationary earth orbiting satellite comprising:

a first optical communication system configured to receive forward-direction user data via a forward optical link between the geostationary earth orbiting satellite and a stratospheric high-altitude communication device, and

a first radio frequency (RF) communication system configured to transmit, via a plurality of RF spot beams, the forward-direction user data received via the forward optical link;

wherein a substantial portion of forward feeder data throughput for all forward RF service link transmissions by the satellite is carried via the forward optical link.

2. The satellite of claim 1 , wherein the substantial portion of the forward feeder data throughput comprises at least 95% of the forward feeder data throughput.

3. The satellite of claim 1 , wherein the stratospheric high-altitude communication device comprises an aircraft operating in a stratospheric altitude.

4. The satellite of claim 3 , wherein the stratospheric high-altitude communication device operates in a range of altitudes between 17 km and 22 km.

5. The satellite of claim 1 , wherein the plurality of RF spot beams includes a first RF spot beam and a second RF spot beam, and wherein the geostationary earth orbiting satellite is configured to:

demultiplex the forward optical link into a plurality of optical channel signals with different wavelengths, the plurality of optical channel signals including a first optical channel signal,

obtain a first intermediate forward RF signal by an optical to electrical conversion of the first optical channel signal,

demultiplex the first intermediate forward RF signal into a plurality of RF subband signals, the plurality of RF subband signals including a first RF subband signal and a second RF subband signal,

generate a first forward RF service link signal by upconverting and amplifying the first RF subband signal,

transmit the first forward RF service link signal via the first RF spot beam,

generate a second RF service link signal by upconverting and amplifying the second RF subband signal, and

transmit the second RF service link signal via the second RF spot beam.

6. The satellite of claim 1 , wherein:

the first RF communication system is further configured to receive reverse-direction user data via a plurality of reverse RF service links including a first reverse RF service link received via a first RF spot beam and a second RF service link received via a second RF spot beam; and

the first optical communication system is further configured to transmit via a reverse optical link the reverse-direction user data received via the plurality of reverse RF service links.

7. The satellite of claim 6 , wherein the satellite is further configured to:

multiplex the first and second reverse RF service links in respective subbands of an intermediate reverse RF feeder link signal;

modulate the intermediate reverse RF feeder link signal onto a first laser beam with a first optical wavelength; and

multiplex the modulated first laser beam into a reverse optical link with the stratospheric high-altitude communication device.

8. A stratospheric high-altitude communication device comprising:

a first radio frequency (RF) communication system configured to receive forward-direction user data via a plurality of concurrent forward RF feeder links; and

a first optical communication system configured to transmit to a geostationary earth orbiting satellite, via a forward optical link, the forward-direction user data received via the plurality of concurrent forward RF feeder links,

wherein a substantial portion of forward feeder data throughput for all forward RF service link transmissions by the satellite is carried via the forward optical link and the plurality of concurrent forward RF feeder links.

9. The stratospheric high-altitude communication device of claim 8 , wherein the substantial portion of the forward feeder data throughput comprises at least 95% of the forward feeder data throughput.

10. The stratospheric high-altitude communication device of claim 8 , wherein the stratospheric high-altitude communication device comprises an aircraft operating at a stratospheric altitude.

11. The stratospheric high-altitude communication device of claim 10 , wherein the stratospheric high-altitude communication device operates in a range of altitudes between 17 km and 22 km.

12. The stratospheric high-altitude communication device of claim 8 , wherein the plurality of concurrent forward RF feeder links are between the stratospheric high-altitude communication device and a ground-based feeder RF terminal (RFT) array including a plurality of ground-based feeder RF terminals (RFTs) positioned at a same RF feeder site, wherein each of the respective RFTs are configured to transmit a respective one of the plurality of concurrent forward RF feeder links.

13. The stratospheric high-altitude communication device of claim 12 , wherein a first forward RF feeder link signal received via one of the plurality of concurrent forward RF feeder links comprises encoded forward-direction user data for delivery to the geostationary earth orbiting satellite.

14. The stratospheric high-altitude communication device of claim 8 , wherein the plurality of concurrent forward RF feeder links includes a first forward RF feeder link and a second forward RF feeder link, and wherein the stratospheric high-altitude communication device is configured to:

downconvert the first forward RF feeder link to a lower RF band to obtain a first downconverted RF signal,

downconvert the second forward RF feeder link to a lower RF band to obtain a second downconverted RF signal,

modulate the first downconverted RF signal onto a first laser beam with a first optical wavelength,

modulate the second downconverted RF signal onto a second laser beam with a second optical wavelength that is different than the first optical wavelength, and

multiplex the modulated first laser beam and the modulated second laser beam into the forward optical link.

15. The stratospheric high-altitude communication device of claim 8 , wherein:

the first optical communication system is further configured to receive reverse-direction user data via a reverse optical link with the satellite; and

the first RF communication system is further adapted to transmit, via a plurality of reverse RF feeder links to a ground-based feeder RF terminal (RFT) array, the reverse-direction user data received via the reverse optical link.

16. The stratospheric high-altitude communication device of claim 15 , wherein the plurality of reverse RF feeder links includes a first reverse RF feeder link and a second reverse RF feeder link, and wherein the high-altitude communication device is configured to:

demultiplex the received reverse optical link into a plurality of optical channel signals with different wavelengths, the plurality of optical channel signals including a first optical channel signal and a second optical channel signal,

obtain a first reverse RF signal by an optical to electrical conversion of the first optical channel signal,

obtain a second reverse RF signal by an optical to electrical conversion of the second optical channel signal,

generate the first reverse RF feeder link by upconverting and amplifying the first reverse RF signal, and

generate the second reverse RF feeder link signal by upconverting and amplifying the second reverse RF signal.

17. The stratospheric high-altitude communication device of claim 15 , wherein the plurality of concurrent forward RF feeder links includes a first forward RF feeder link and a second forward RF feeder link and the plurality of reverse RF feeder links includes a first reverse RF feeder link and a second reverse RF feeder link, and wherein the high-altitude communication device is configured to:

downconvert the first forward RF feeder link to a lower RF band to obtain a first downconverted RF signal,

downconvert the second forward RF feeder link to a lower RF band to obtain a second downconverted RF signal,

modulate the first downconverted RF signal onto a first laser beam with a first optical wavelength,

modulate the second downconverted RF signal onto a second laser beam with a second optical wavelength that is different than the first optical wavelength,

multiplex the modulated first laser beam and the modulated second laser beam into the forward optical link,

demultiplex the received reverse optical link into a plurality of optical channel signals with different wavelengths, the plurality of optical channel signals including a first optical channel signal and a second optical channel signal,

obtain a first reverse RF signal by an optical to electrical conversion of the first optical channel signal,

obtain a second reverse RF signal by an optical to electrical conversion of the second optical channel signal,

generate the first reverse RF feeder link by upconverting and amplifying the first reverse RF signal, and

generate the second reverse RF feeder link signal by upconverting and amplifying the second reverse RF signal.

18. The stratospheric high-altitude communication device of claim 8 , further comprising:

a plurality of sensors; and

a pointing, acquisition, and tracking (PAT) controller configured to perform, based on at least sensor data obtained from the sensors, optical pointing of a forward optical link signal between the stratospheric high-altitude communication device and the satellite.

19. The stratospheric high-altitude communication device of claim 12 , wherein the plurality of ground-based RFTs are arranged in a compact arrangement in which distances between individual ground-based RFTs are minimized but also maintain interference between the plurality of concurrent forward RF feeder links below a predetermined level.

20. The stratospheric high-altitude communication device of claim 15 , wherein the plurality of ground-based RFTs are arranged in a compact arrangement in which distances between individual ground-based RFTs are minimized but also maintain interference between the reverse RF feeder links below a predetermined level.