BACKGROUND ART Over the past decade, a number of satellite systems have been proposed. The largest of these, TeledesicTM, is scheduled to begin service in the year 2004. TeledesicTM will comprise a constellation of over two hundred low Earth orbit satellites, and will provide broadband telecommunications around the globe. The Iridium System became operational in 1998, and employs sixty-six satellites in low Earth orbit to offer voice and paging services to subscribers using handheld phones. GlobalstarTMwill inaugurate its service in 2000, utilizing forty-eight satellites to link special handsets that will communicate with both the orbiting spacecraft and conventional terrestrial cellular antennas. Hughes plans to launch a new geostationary system called SpacewayTM that is expected to furnish two way direct-to-satellite Internet connections to homes and businesses in 2001.

Each of these new satellite networks will offer unprecedented new forms of communications services. Some of these networks will operate in relatively close, low Earth orbits at altitudes of about 435 miles, while others will operate at distant geosynchronous orbits, at altitudes of about 23,000 miles. Each of these systems will require complex switching and beam control methods to insure reliable and uninterrupted service. These new networks will need to communicate with a wide variety of terminals, including large ground stations, fixed and mobile receivers and handheld phones. In addition, all of these constellations will require connections to public and private switched networks, including traditional land lines and cellular systems.

Several previous efforts to enhance, coordinate and interconnect worldwide communications capabilities have met with limited success. A few previous systems are briefly described below.

Robert R. Newton discloses a Multipurpose Satellite System in his U. S. Patent No. 3,497,807.

Newton describes a system in which any point on Earth is always within the line of sight of some satellite and any satellite is always within the line of sight of an adjacent satellite in the same orbital plane. See Newton, Column 2, Lines 4-7.

U. S. Patent No. 4,135,156 by Sanders et al., entitled Satellite Communications System Incorporating Grouszd Relay Station Through Which Messages Between Terminal Stations Are Routed, contains a description of a satellite relay communications system that includes a ground relay station

arranged so that each message from one subscriber to another is relayed by the satellite relay to the ground relay, processed by the ground relay and then transmitted to the second subscriber by way of the satellite relay. See Sanders et al., Abstract, Lines 1-6.

Paul S. Visher discloses a Satellite Arrangement Providing Effective Use of the Geostationary Orbit in his U. S. Patent No. 4,375,697. His Patent describes a satellite squadron or cluster formation which is disposed in a predetermined location in geostationary orbit. See Visher, Abstract, Lines 1-2.

U. S. Patent No. 5,666,648, issued to James R. Stuart, describes a telecommunications system that includes twelve satellites which are deployed in polar low Earth orbits. A preferred embodiment provides a system for transmitting a message between two terminals on the ground through a store-and-forward network. The store-and-forward relay method takes advantage of the geometry of a system which allows the satellites to fly over different parts of the globe frequently. A first satellite traveling in a first orbit receives and stores a message from a sending terminal or gateway on the surface of the Earth. As it passes near a relay station near a Pole of the Earth, it transmits the stored message from the sending terminal to the relay station. The message is stored at this relay station until a second satellite moving within a second orbit flies within range. The relay station then sends the stored message up to the second satellite which stores the message and finally transmits it to another receiving terminal or a gateway elsewhere on the Earth. The receiving terminal then forwards the message to the addressee. A satellite can send its stored message directly to a receiving terminal without the using the polar relay station if that path is faster.

In a related U. S. Patent No. 5,678,175, Stuart et al. disclose a satellite system which uses a combination of inclined, polar and Equatorial orbits to increase the capacity and speed of the message handling. To provide communication services to virtually every point on the globe, the system requires a substantial number of terrestrial relay stations, terminals and gateways. Such a system has an objective of supplying a worldwide low cost system. It would be beneficial if such a system did not require expensive, complex, large and aesthetically displeasing ground stations.

In U. S. Patent No. 5,822,680, Stuart et al. disclose a communication system and methods for sharing a common communication frequency by producing a spatial isolation of signals.

A new system which would provide reliable, efficient and low-cost interconnections and relay capabilities for the new satellite and terrestrial networks that will roll out services in the next few years would greatly enhance the present telecommunications business. Such a system would ideally offer a short communications path length and a high elevation angle. The development of such a system would constitute a major technological advance, and would satisfy a long felt need in the telephone, paging, television, radio, entertainment and data conveyance industries.

DISCLOSURE OF THE INVENTION The present invention comprises methods and apparatus for conveying or relaying signals to, from or among a wide variety of sources and destinations. The invention utilizes platforms or vehicles which operate above the surface of the Earth, but below orbital altitudes. In one embodiment of the invention, an unmanned, automated platform is placed above a populated region at an altitude of approximately 70,000 feet. This altitude is well above the range of commercial aircraft, but is far below low Earth orbit.

This platform is capable of operating for long periods of time, and carries equipment which automatically maintains its position over a desired location. The invention includes communications payloads which enable it to receive signals from, or to transmit signals to, a wide variety of terminals in space, in the atmosphere, on the oceans or on the ground. These signals may be conveyed using electromagnetic waves at radio frequencies, or at optical or other frequencies. One embodiment of the invention may serve as an intermediate relay for a variety of signal sources and targets, while another may serve as a data gathering or remote sensing system.

The invention is capable of providing service to rockets, reusable launchers or other space vehicles, which may include spacecraft in low, medium, high, geosynchronous, super-synchronous, lunar, planetary, interplanetary, orheliocentricorbits ; spacecraftin otherballistic, sub-orbital ornon-orbital flight paths ; or spacecraft located at or near lunar, planetary or deep-space locations. The invention may also furnish service to ground terminals, which may be fixed, portable or mobile ; and to airborne vehicles, which may include both piloted or unmanned airplanes and lighter-than-air ships.

The present invention will be used to enhance a broad spectrum of communications services, including voice and high-capacity data transmissions, paging, asset monitoring, broadband Internet and entertainment channels, and to enhance conventional land lines and terrestrial wireless, airborne and spaceborne communications networks.

An appreciation of the other aims and objectives of the present invention and a more complete and comprehensive understanding of this invention may be obtained by studying the following description of a preferred embodiment and by referring to the accompanying drawings.

A BRIEF DESCRIPTION OF THE DRAWING Figure 1 is a schematic illustration which reveals one embodiment of the present invention, and which also reveals some of the links to and from this embodiment and ground terminals. The term"ground terminal"includes, but is not limited to, all terminals that are fixed (stationary), portable (movable) or mobile (often in motion) on land and/or sea. All of these ground terminals may have receive-only, transmit- only or both transmit and receive capabilities.

Figure 2 is a schematic illustration which reveals another embodiment of the present invention, and which also reveals some of the links to and from this embodiment and airborne terminals. The term "airborne terminal"includes, but is not limited to, all terminals on any apparatus, heavier-than-air (e. g., an

airplane) or lighter-than-air (e. g., a blimp) that flies, floats or is levitated above the ground in or through the atmosphere using the buoyancy, fluid dynamics of the atmosphere or any other levitating mechanism.

All of these airborne terminals may have receive-only, transmit-only or both transmit and receive capabilities.

Figure 3 is a schematic illustration which reveals yet another embodiment of the present invention, and which also reveals some of the links to and from this embodiment and ballistic, sub-orbital terminals.

The term"ballistic sub-orbital terminals"includes all terminals on any apparatus (e. g. an expendable launcher, a reusable launch system, a re-entry vehicle, etc.) that is in unsustainable flight in the atmosphere, is sub-orbital or is in ballistic free fall before or after leaving the atmosphere. All of these ballistic, sub- orbital terminals may have receive-only, transmit-only or both transmit and receive capabilities.

Figure 4 is a schematic illustration which reveals another embodiment of the present invention, and which also reveals some of the links to and from this embodiment and spaceborne terminals in various Earth orbits. Spaceborne terminals on satellites may be in any orbit, besides the ones shown: Low Earth Orbits (LEO, 300km-3000km), MediumEarthOrbits (MEO, 8,000km-16, 000km), Highly Elliptical Orbits (HEO) which include highly eccentric orbits (e. g., Molniya orbits, Geotransfer orbits, etc.), Geostationary and/or Geosychronous Orbits (GSO, 35,786 km), Super-synchronous orbits (above GSO altitude 35,786 km, with longer periods). All of these spaceborne terminals may have receive-only, transmit-only or both transmit and receive capabilities.

Figure 5 is a schematic illustration of the links to and from spaceborne terminals in interplanetary, heliocentric orbits and on, above, or on-orbit around the moon (lunar) and/or other planets and other solar system bodies and the disclosed invention.

Figure 6 is a schematic illustration of an example of multiple receive and transmit beams of one embodiment of the invention. The beams of the sub-orbital platform communications system may be from any antenna configuration, e. g., fixed or steerable (using mechanical or electronic steering), phased array or parabolic reflector, single or multiple beam per antenna, etc.

Figure 7 is a functional block diagram of one embodiment of the invention, showing signal processing capabilities for a bent-pipe repeater.

Figure 8 is a functional block diagram of one embodiment of the invention, showing signal processing capabilities for on-board switching.

Figure 9 is a functional block diagram of one embodiment of the invention, illustrating capabilities for multiple beams/channels with an on-board switching.

Figure 10 is a functional block diagram of one embodiment of the invention, illustrating ground system signal processing for a ground-based switching.

BEST MODE FOR CARRYING OUT THE INVENTION I. A Preferred Embodiment of the Invention The present invention utilizes platforms operating above the ground, but below orbital altitudes, to furnish signal relays to a variety of conventional and newly proposed communication networks. In general, these platforms fly in the atmosphere above the maximum flight range of commercial aircraft, but below the lowest orbital altitudes, which are generally around 100 miles. In general, the platforms are unmanned, and are equipped with sensors that enable precise monitoring of their location and altitude above the Earth. The platforms are also generally equipped with engines, allowing them to automatically generate thrust which keeps them precisely positioned over their service territories. The platforms are linked together by transceivers which directly, or via ground, airborne and/or spaceborne connections, enable them to form a stratospheric regional, nationwide, continental or global communications network.

In one embodiment, the invention may be utilized to relay signals from a constellation of satellites in Earth orbit to terminals below the platform. When used in this Specification and in the Claims that follow, the phrase"below the platform"or any equivalent expression refers to locations that are generally closer to the surface of the Earth than the location of the platform. Similarly, the phrase"outside the Earth's atmosphere"or any equivalent phrases connote a location which is above an altitude required to sustain an orbit, or a location on the Moon, on a planet or otherwise in space beyond the Earth.

In one preferred embodiment of the invention, electromagnetic wave signal links (2-11,17-24,29- 42,49-54,60-67,73-84) in beams emanating from ground terminals (12-16,25-28), airborne terminals (1, 43-47) sub-orbital, ballistic terminals (55-57), spaceborne terminals in Earth orbit (68-71), and spaceborne terminals beyond Earth orbit (85-90) are collected by one embodiment of the invention and re-transmitted to ground terminals (12-16,25-28), airborne terminals (1,43-47) sub-orbital, ballistic terminals (55-57), spaceborne terminals in Earth orbit (68-71), and spaceborne terminals beyond Earth orbit (85-90). This embodiment routes signals between its receive and transmit beams (91-93) (fixed or steered) and receive channels (91) and transmit channels (92) using bent-pipe repeaters (Figure 7), using on-board processing (Figures 8 & 9) before re-transmission, or by relaying the signals to and from ground based processing (Figure 10) before re-transmission. The present invention uses relayed electromagnetic wave signals which may be anywhere in the frequency range from 3 0 Hertz (Extremely Low Frequency band) to 3000 Terahertz (Optical frequencies), as shown in Table One.

Table One: Frequency Ranges & Band Designations Frequency Range Acronym Designation 30-300 Hertz ELF Extremely low frequency 300-3000 Hertz VF Voice frequency 3-30 Kilohertz VLF Very low frequency 30-300 Kilohertz LF Low frequency 300-3000 Kilohertz MF Medium frequency 3-30 Megahertz HF High frequency 30-300 Megahertz VHF Very high frequency 300-3000 Megahertz UHF Ultra high frequency 3-30 Gigahertz SHF Super high frequency (cm wave) 30-300 Gigahertz EHF Extremely high frequency (mm wave) 300-3000 Gigahertz VEHF Very extremely high frequency 30-3000 Terahertz Optical frequencies Table One provides an overview of some of the frequency bands that may be used to implement the present invention. In this Specification and in the Claims that follow, the term"electromagnetic waveform"refers generally to any propagated or non-propagated signal such as a quasi-static field that is conveyed or furnished using frequency bands that are below the sensible limits of human eyesight. In alternative embodiments, the invention may be implemented using optical, or even higher, frequency bands of radiation. In this Specification and in the Claims that follow, the term"optical impulse"refers to signals emanated using the generally visible spectra, while the term"ultra-optical impulse''relates to signals that are conveyed using frequency bands that exceed the frequencies of sensible light. Similarly, the term "radiation interface"encompasses any antenna, sensor or device which emits or gathers any electromagnetic, optical or other signal, wave or impulse.

II. Advantages of the Invention One great advantage of the present invention is that they furnish a communications node which is maintained at a optimal location: below the lowest satellites, but high above the tallest towers or antennas connected to terrestrial networks. This enormous benefit offers a optimized communications architecture-an unobscured line of sight to all signal sources and customers, a short path length and a high elevation angle.

The specific benefits of creating this optimized communications architecture are summarized in Table Two: Table Two: Benefits of an Optimized Communications Architecture Platform is lowest, closest non-orbiting node in network Smaller spots Higher frequency re-use Higher density of customers serviced Platform Offers Shortest Signal Path Length Smaller customer premise antennas Lower transmit power Stationary in sky Clear line-of-sight Easily upgradable with new technologies, new services and new frequencies Single node for access and interconnection to space and terrestrial wired and wireless networks Optimal Location Above Terrestrial Towers and Subscribers Single tower coverage with one set of equipment Clear line-of-sight : no blockages Instant roll-out Easily upgradable with new technologies, new services and new frequencies Single node for access and interconnection to space and terrestrial wired and wireless networks Another advantage offered by the present invention is the placement of switching, signal processing and beam control equipment aboard a platform which is capable of lifting heavy and high-power payloads to its operating altitude. By utilizing switching, signal processing and beam control equipment aboard a sub-orbital platform, satellite systems can reserve their precious and severely limited switching and power resources for other tasks.

III. An Alternative Embodiment of the Invention The system consists of one or more transceiving satellites (i. e., capable of both receiving and transmitting information), one or more unmanned or manned air vehicles (U/MAVs) featuring a transceiver frequency converter system, and one or more transceiving units of Gateway/Customer Premise Equipment (Gateway/CPEs). In an altemative embodiment ofthe invention, sub-orbital vehicles may be employed as relays. The satellites may be low earth orbit satellites, medium earth orbit satellites, high altitude elliptical satellites, geosynchronous earth orbit satellites, interplanetary craft and/or ships in orbit about other celestial or planetary bodies, moons or asteroids. The satellite is capable of transmitting and receiving information at optical and lower and higher microwave frequencies, the U/MAV is capable of transmitting and receiving information at optical, higher microwave, and lower microwave frequencies, and the Gateway/CPE is capable of transmitting and receiving information at lower microwave frequencies. The U/MAV may be powered by an onboard fuel supply, atransmission of microwave energy from a microwave transmitting unit, solar cells, a combination of the foregoing, or other power systems. Other implementations of the invention may involve the use of a wide variety of combinations of up-link and down-link frequencies.

Data transmission can originate in any one of four ways. First, Gateway/CPEs can transmit data to satellites. Second, satellites can transmit data to U/MAVs. Third, Gateway/CPEs can transmit data to U/MAVs. Lastly, U/MAVs can initiate transmissions to either satellites or Gateway/CPEs. Such transmitted data includes, but is not limited to, video and voice data, remotely sensed data, television signals, and telescopic data.

The underlying principal of the system is that the U/MAV's payload up-converts (changes to a higher frequency) signals which are being transmitted away from the earth's atmosphere, and conversely down-converts (changes to a lower frequency) signals which are being transmitted towards the earth's atmosphere. Thus, optical or higher microwave signals going to the U/MAV from satellites (whether the signal originated directly from the satellites or Gateway/CPEs) would be down-converted by the U/MAV's high speed, onboard data switch, router, frequency converter or other similar device before being relayed to Gateway/CPEs. On the other hand, lower microwave signals going to the U/MAV from Gateway/CPEs would be up-converted by the U/MAV's payload, and then relayed to one or more satellites. Typically, data is simultaneously transmitted both from a Gateway/CPE through a U/MAV to a satellite, and from a satellitethrough aU/MAVto aGateway/CPE, withbothup and down-converting occurring simultaneously.

The preceding description discloses one particular implementation of this embodiment of the invention. The invention includes other complementary implementations, including those which involve the payload down-converting signals which are being transmitted away from the earth's atmosphere to a lower frequency, and conversely up-converting signals going to the U/MAV.

The U/MAV may also be used for up/down-converting in a configuration where data is sent from Gateway/CPEs to a U/MAV, the data is up-converted, crosslinked to another U/MAV (either the first or

a subsequent U/MAV could do the up-conversion), and sent to one or more satellites. The data transmission can also travel from satellites to crosslinked U/MAVs and then to Gateway/CPEs. As disclosed in the previous paragraph, such transmissions can occur simultaneously, and such a system may involve two or more U/MAVs. Other complementary implementations of this embodiment may involve signals having different frequency bands conveyed in opposite directions, and opposite conversion processes.

Additionally, the invention allows communications to go from a first Gateway/CPE to a first U/MAV, and then to a first satellite. The transmission can then be relayed from the first satellite to a second satellite, then to a second U/MAV and finally to a second Gateway/CPE. More generally, any multiple combinations of Gateway/CPEs, U/MAVs and satellites can be combined to transmit data.

The primary advantage of the aforementioned system is that overall data throughput is increased by allowing satellites to transmit at the more efficient optical or higher microwave frequencies. The U/MAV receives these optical or higher microwave transmissions before they are attenuated by the earth's atmosphere, converts the transmission to a lower microwave frequency which is not as adversely affected by the earth's atmosphere as higher frequencies, and then transmits the converted data to Gateway/CPEs.

The U/MAV payload up-converts and down-converts signals on a relative basis, i. e. what might be considered a higher frequency requiring down-conversion in one instance may be considered a lower frequency requiring up-conversion in another instance. As an example of one particular implemenation, the U/MAV payload typically would up-convert signals transmitted from Gateway/CPEs in the 1-51 gigahertz (GHz) range to higher optical frequencies, and would down-convert signals transmitted from satellites at optical frequencies to the 1-51 GHz range. However, the U/MAV could receive signals from Gateway/CPEs at 1 GHz, and up-convert to 47 GHz (microwave frequency) before transmission to satellites. Conversely, the U/MAV could receive signals from satellites at 47 GHz, and down-convert it to 1 GHz before transmission to Gateway/CPEs.

CONCLUSION Although the present invention has been described in detail with reference to one or more preferred embodiments, persons possessing ordinary skill in the art to which this invention pertains will appreciate that various modifications and enhancements may be made without departing from the spirit and scope of the Claims that follow. The various alternatives for providing sub-orbital platforms or vehicles that have been disclosed above are intended to educate the reader about preferred embodiments of the invention, and are not intended to constrain the limits of the invention or the scope of Claims. The List of Reference Characters which follow is intended to provide the reader with a convenient means of identifying elements of the invention in the Specification and Drawings. This list is not intended to delineate or narrow the scope of the Claims.

INDUSTRIAL APPLICABILITY The Sub-OrbitalRelays will be capable ofproviding service to rockets, reusable launchers or other space vehicles, which may include spacecraft in low, medium, high, geosynchronous, super-synchronous, lunar, planetary, interplanetary, orheliocentric orbits; spacecraft in other ballistic, sub-orbital ornon-orbital flight paths; or spacecraft located at or near lunar, planetary or deep-space locations. The invention may also furnish service to ground terminals, which may be fixed, portable or mobile; and to airborne vehicles, which may include both piloted or unmanned airplanes and lighter-than-air ships.