Abstract: A positioning device has a reception unit for receiving navigation messages transmitted continuously in a time series from positioning information satellites orbiting the Earth and determines the location of the positioning device based on the navigation messages received by the transmission unit. Each navigation message is segmented into a plurality of data transmission blocks that are transmitted sequentially, a portion of the data transmission blocks carry almanac data containing orbital information for all positioning information satellites including the positioning information satellite transmitting the received navigation message, and the data transmission blocks carrying the almanac data are transmitted non-contiguously. The positioning device also has signal discrimination unit for identifying the start of receiving a data transmission block containing the non-contiguously transmitted almanac data, and identifying the end of receiving the data transmission block containing the almanac data.

Abstract: A communication system has a high altitude communication device that has an antenna for directing beams to a fixed cell pattern with a polarity of cells. A specific pattern of cells having the same communication resource is provided. Preferably, cells having the same resource are separated. The antenna is shaped to suppress interference with locations having the same resource. The areas not having the same resource are not suppressed to allow the system to have maximum capacity and allow a smaller antenna aperture.

Abstract: A method of controlling a satellite communication system, a timing unit, and a control unit of a timing unit. The method comprises dividing the coverage area of the satellite communication system into one or several geographical areas; positioning one or several timing units in at least one geographical area; determining which of the satellites of the satellite communication system are visible in each particular geographical area; controlling the timing unit with a control unit, in order to minimize the time difference within the system, to listen to one or several satellites visible in each particular geographical area, the signals received from the satellites by the timing unit fulfilling a predetermined condition; synchronizing a predetermined number of geographical areas with each other by means of the control unit of the system such that the time difference within the system is minimized in a predetermined combination area of geographical areas.

Abstract: A cellphone system comprises a GPS reference station located with a telephone cell site. Such GPS reference station tracks the GPS satellites visible to its local area and estimates the Doppler for each such GPS satellite. The system also includes mobile GPS receivers and cellphones that move around and through the operational area of the cell site. It is assumed that the satellite Dopplers seen by the GPS reference station will have insubstantial differences with the true Dopplers observed by other GPS receivers operating within the cell site's service area. The Doppler estimates are thus routinely communicated over a wireless telephone channel to the mobile GPS receivers and cellphones that register locally. Such mobile GPS receivers then can confidently adopt the surrogate Doppler estimates as a center starting point for their initialization frequency searches. The time required for such mobile GPS receivers and cellphones to initialize and provide a first fix is thereby substantially reduced.

Abstract: Method and apparatus for providing accurately synchronized timing signals at mutually distant locations employs a GPS or similar receiver at each location. These receivers are interconnected by a communications network, and exchange data over the network to agree a common timing reference.

Abstract: A satellite positioning device is disclosed for determining position based on received satellite navigation signals and a received non-satellite signal. A local clock controls the epoch period of a satellite signal processor. Correction signals are applied to the local clock in order to improve the synchronization between the satellite signal processor and the non-satellite signal processor.

Abstract: A method for providing location information. In the method a demand of providing location information of a terminal of a second user is accepted from a terminal of a first user. An approval of the location information provided to a terminal of the second user is requested, which depends on a request of providing the location information. A reply for approving providing the location information is received from the second terminal. Map information of the first and the second user which includes each other's location information is then generated, the location information which was provided from the first and second user's terminal is synthesized, and map data chosen based on the location information from the data base, when providing the location information, is approved. The generated map information is displayed at least on the first user's terminal.

Abstract: Shows orbit-constellation of satellites that appears virtually geosynchronous.

Abstract: This disclosure provides a communications system using a span-loaded flying wing, traveling at relatively slow speeds, that can remain airborne for long periods of time. The communications system uses the airplane as a long term high altitude platform that can serve at lest one of a number of potential functions. One function is to link to a ground station using radio wave signals and a satellite using optical signals. Another function is to serve as a relay station between ground communication nodes and individual end-users. Because the aircraft can tightly hold a station, the end-user's antennas do not need to be continuously adjustable. For such a system, a large number of aircraft can be used, with the end-user antennas being configured for a narrow beamwidth so as to allow frequency reuse for different communication links.

Abstract: The present invention relates to a global network based vehicle safety and security system and method. In this regard, a global network based data processing resource can wirelessly data communicate with an in-vehicle device to control and monitor vehicle safety and security. In addition, data communicated between the vehicle and global network based data processing resources can control, monitor, and track the vehicle as well as data communicate command and control functions, such as disabling vehicle operation. Furthermore, alarm and alerting functions can effectuate the notification of other data processing resources and or other agency or emergency resources. Vehicle and in-vehicle device data, including safety and security data gathered at data processing resources can be utilized to effectuate a wide variety of data dissemination. Such data dissemination can include warning, alarm, safety, or security determinations, and or other reporting or analysis related to vehicle safety and or security.

Abstract: A transmission or communication system, wherein plural individual elliptical orbits are so defined that an individual right ascension of a north-bound node is established with a designated angle. An artificial satellite is travels on a respective ones of the plural individual elliptical orbit and a group of artificial satellites arranged on respective ones of the plural individual elliptical orbits are used so that at least one of the artificial satellites having a communication system is always viewable within a pre-defined range of operational elevational angle in a zenith direction from a service area. The group of artificial satellites are on respective orbits obtained by combining an inclination angle and an eccentricity squared of the individual elliptical orbit so that a right ascension of north-bound node is a designated angle and a time period during which respective ones of the group of artificial satellites is viewable from ground is substantially identical.

Abstract: An array of satellites which is virtually geosynchronous. Each satellite is in an elliptical orbit. The apogee portion of each elliptical orbit is over one of the regions of interest. Each satellite is virtually geosynchronous during its apogee portion, over the region of interest. When it leaves the apogee portion, the satellite goes to another of the regions of interest, and acts virtually geosynchronous over that region.

Abstract: A method and apparatus for correlating a satellite signal with a reference code is described. In an example, samples of a satellite signal having a repeating code are received. At least one fast convolution between the samples and the pseudorandom reference code is performed. A correlation peak is detected within a result of the at least one fast convolution. A code phase of the repeating code relative to the pseudorandom reference code is estimated at the correlation peak. The samples are then correlated with the pseudorandom reference code using the code phase as an initial value.

Abstract: A system, apparatus and method provide wireless communications to a geographical area. The system includes at least one atmospheric platform serving as a central relay or node using a star network topology for the geographic area. The atmospheric platform carries a payload that comprises communications equipment. The system further includes a plurality of user equipment units located within the geographic area and at least one ground station or gateway for providing an information pathway between the user equipment units. The gateway has network processing and switching equipment for routing the information between the users. A wireless trunkline carries signals between the gateway and the atmospheric platform. The apparatus and method comprise gateway and payload uplink portions and downlink portions. The downlink portions aggregates and de-aggregates user generated information from the platform to the gateway.

Abstract: A method of determining the position of geostationary satellites by means of signals of at least one navigation satellite. A determination is made of data concerning the transit times of the signals from the at least one navigation satellite to the geostationary satellite by a device of the geostationary satellite, and a determination is made of navigation data of the at least one navigation satellite by an independent navigation device. A determination is made of data concerning the system time of the at least one navigation satellite by an independent navigation device, and a data exchange occurs between the geostationary satellite and the navigation device in order to determine position data of the geostationary satellite from the transit times, the navigation data as well as the system time of the at least one navigation satellite.

Abstract: An elliptical satellite communication system including a constellation of satellites which orbit the earth at a height less than that necessary for geosynchronous orbits but which simulate the characteristics of geosynchronous orbits. The satellites' velocity near the apogee portion of their orbit approximates the rotational velocity of the earth, and during that period appear to hover over the earth. The ground stations on the earth always communicate with a satellite at or near its apogee, and hence that satellite appears to the ground station to hover over the earth. During the times when the satellite is outside the apogee portion, its communication is shut off to prevent any possibility of interfering with geosynchronous satellites and its power supply is used to charge a battery on the satellite. Thus, the power supply of the system can be reduced by an amount equivalent to the percentage of time the satellite is not used.

Abstract: The present invention relates to an antenna alignment meter which comprises a receiver for detecting a signal with predetermined characteristics and outputting data pertaining to the detection of the signal, and a controller responsive to the data from the receiver for controlling generation of an indicator that signal has been received. The meter can be used for aligning an antenna with a signal source. The meter is arranged to monitor signals received by the antenna and to provide an indication of correct alignment of the antenna with a desired signal source when a signal of a predetermined frequency, polarization, symbol rate and error correction is received.

Abstract: A broadcasting or transmitting system using an artificial satellite. The artificial satellite is placed into an orbit in which individual artificial satellites orbit on an elliptical orbit so that at least one of the artificial satellites is always viewable within a pre-defined range of operational elevational angles in a zenith direction from a service area. A group of the artificial satellites are satellites on respective different orbits obtained by combining an inclination angle and an eccentricity squared of said elliptical orbit so that a time period during which one artificial satellite of the group of the artificial satellites is viewable from ground is substantially identical to a time period during which another artificial satellite of the group is viewable from the ground.

Abstract: A method for aligning an antenna polarization axes of a dual polarized end-user terminal having an antenna. The antenna is aligned with a satellite in relation to azimuth and elevation. The end-user terminal is configured in an alignment mode to produce a first output corresponding to a first component of a received signal parallel to a first polarization axis of the antenna and a second output corresponding to a second component of the received signal parallel to a second polarization axis of the antenna. The first polarization axis is orthogonal to the second polarization axis. The method includes the steps of: receiving a linearly polarized signal; autocorrelating the first output and the second output to produce a measurement of autocorrelation; and adjusting the antenna polarization axes to minimize the measurement of autocorrelation.

Abstract: An antenna controller comprises an antenna beam control unit for controlling the direction of an antenna beam of an antenna, an inertial navigation system for acquiring motion information on a motion of the mobile body, an antenna beam direction calculation unit for calculating the direction of the antenna based on the motion information from the inertial navigation system to direct the antenna beam toward the geostationary satellite, a motion information acquisition unit for separately acquiring motion information on the motion of the mobile body, and a motion estimation unit for estimating a delay of the motion information acquired by the inertial navigation system based on the motion information acquired by the inertial navigation system and the motion information acquired by the motion information acquisition unit, and for estimating motion information to be sent to the antenna beam direction calculation unit in consideration of the estimated delay.

Abstract: A system (20) and method (30) for estimating the location of a terrestrial-based user terminal (23) is provided. The user terminal (23) is capable of measuring the relative signal strengths of a plurality of spot beams pilot signal emitted from a geostationary satellite (22). The user terminal (23) then estimates its position based on the measured relative signal strengths. Using this approach, the user terminal (23) can quickly determine its location without prior knowledge of its position or delay time.

Abstract: The antenna system comprises a reflector which can be motionless, a source device and a device for treating the signals received by the source device. The system comprises means for automatically tracking the satellite that deviates from its initial position to an inclined orbital path.

Abstract: Clocks are synchronized using a reference clock in two possible ways. One method uses two-way communication between a reference clock and a moving clock. The other method uses one-way communication from the moving clock.

Abstract: A method and apparatus for locating mobile device over a broad coverage area using a wireless communications link that may have large and unknown latency. The apparatus comprises at least one mobile device, a reference network, a position server, a wireless carrier, and a location requester. The mobile device is in communication with the wireless carrier and receives global positioning system (GPS) signals from a plurality of satellites in the GPS satellite constellation. The reference network is coupled to the position server and provides GPS data. The mobile receiver receives GPS signals, performs rudimentary signal processing and transmits the processed signals to the wireless carrier. The wireless carrier passes the signals on to the position server. The position server processes the mobile receiver's GPS data and the reference network ephemeris data to identify the location of the mobile receiver. The location is sent to the location requester.

Abstract: A satellite subsystem for a satellite employs a reconfigurable communications payload and active array antennas. The subsystem includes an active receive array antenna having a reconfigurable beam forming network for forming input beam signals from input signals received by the receive antenna from sources. An input switch matrix power divides the input beam signals into sets of input beam signals. Each of the channel signals corresponds to a respective channel of the input beam signals. The subsystem further includes a channelizer having a plurality of channel processors each receiving at least one input beam signal from the input switch matrix. The channel processors filter the input beam signals into channel signals. Each of the channel signals corresponds to a respective channel of the input beam signals. The channel processors change the frequency of at least one channel signal to route the at least one channel signal to a different channel than the respective channel of the input beam signals.

Abstract: The invention relates to a method of locating a jammer (14) of a satellite telecommunications system (10). To locate the jammer, at least two of the following three measurements are performed: a measurement of the difference between the instant of arrival at the telecommunications satellite and at a detection satellite (16) of signals transmitted at the same time by the jammer (14), the detection satellite being used solely for detection purposes; a measurement of the difference between the frequencies received by the telecommunications satellite and by the detection satellite, for a signal transmitted by the jammer; and an interferometric measurement of the angle between a direction associated with the detection satellite and the straight line between said satellite and the jammer (14).

Abstract: A system of inclined geosynchronous satellite orbits has a service area defined on a surface of the earth. The service area has elevation angles greater than a predetermined minimum elevation angle from the horizon. A satellite has an orbit with respect to the earth having a sky track when viewed from within said service area. An operating arc is defined by a subset of points on the sky track within the service area. The satellites operate consecutively on the operating arc.

Abstract: A GPS receiver has a plurality of data demodulator circuits assigned to a plurality of GPS satellites, respectively, and a data memory which stores detailed orbit information of the GPS satellites. The GPS receiver searches for satellites the detailed orbit information of which was stored in the memory previously. When these searched GPS satellites are acquired, the GPS receiver executes satellite frame synchronization determination processing to check for an agreement among predetermined data included in satellite data transmitted from the acquired GPS satellites. When the searched GPS satellites cannot be acquired or the predetermined data do not agree, the GPS receiver executes a single-satellite frame synchronization determination processing to check for an agreement of predetermined data included in a plurality of frames of the satellite data. The GPS receiver starts positioning processing in response to an establishment of agreement to calculate its position.

Abstract: A method of controlling an antenna signal combiner in a vehicle having multiple antenna elements. The method comprises the steps of receiving broadcast signals from the antenna elements. An antenna beam is steered toward a first steering angle. Navigation data is generated in response to a navigation sensor, the navigation data identifying a relative changes in vehicle direction. The antenna beam is steered toward a second steering angle in response to the relative change in vehicle direction.

Abstract: In a wireless location system (WLS) including a plurality of geographically separated receiver systems, a system for synchronizing the respective receiver systems includes the use of an enhanced GPS receiver including a mechanism for receiving GPS signals and removing at least a portion of the timing instability of the GPS signals. An output of the enhanced GPS receiver is provided to a low phase noise phase-locked loop circuit that is used to produce reference signals with less than 0.01 degrees RMF of phase noise.

Abstract: A satellite broadcast and communication system employing a constellation of satellites in highly elliptical and highly inclined orbits, where the satellites remain almost stationary relative to ground users, describing a small loop in the sky around the apogee of the orbit for long periods of time. A user on the ground with conventional directive antenna will be provided with continuous communication services without interruption, 24 hours per day. The small loop where the satellites are operational is located around the highest latitude of the orbit. Therefore, it will have a high angular separation from satellites operating in the equational geostationary satellite orbit (hereafter more simply referred to as the geostationary satellite orbit), thus enabling a full sharing of the frequency hands used by the geostationary satellite orbit systems, without causing any interference between the two types of satellite network systems, and without the need for any interference migrating factors.

Abstract: A communication system, wherein plural elliptical orbits in which an apogee is located on a specified service area are so defined that an individual right ascension of north-bound node may be established with a designated angle. A satellite is made to travel on an individual elliptical orbit and a group of satellites to be arranged on said elliptical orbits are used so that at least one of artificial satellites having a communication system may be always viewable within a pre-defined range of ascending vertical angle in a zenith direction from the service area.

Abstract: A synchronized timing system is disclosed for one or more of a plurality of network interconnected computers. The system utilizes a global satellite system and includes a receiver device for detecting out-of-phase signals from a plurality of satellite sources of the satellite system. A mechanism is provided for processing and phase correlating these signals to generate a single absolute time reference signal therefrom. An interface device is disposed in each computer for receiving the reference signal and adapting this signal as the internal master clock reference for the operating system of the computer. Finally, a mechanism interconnects each computer in the network of computers to synchronize the internal master clocks of the computers to the absolute time reference signal to create a plurality of network interconnected time synchronized computers.

Abstract: In order to achieve a considerable reduction of the outlay required on the ground in connection with the accurate calculation of the exact orbital position of each individual satellite of a constellation, first the exact orbital position of a preferably central master satellite of a sub-group of satellites embodied as a special formation is determined. This calculation is performed autonomously on board the satellite by means of customary measurements supported from the ground, or respectively by means of GPS, MANS, etc. Then the exact position of all other satellites in the same formation is determined from range and pointing data, which are provided by each IS link terminal. These pointing data are well known after the establishment of the inter- satellite link and are continuously updated.

Abstract: A system for acquiring the beacon of a satellite and synchronizing data transmission between the satellite and a ground terminal is disclosed. The ground terminal conducts a search for a satellite to be acquired. The search may be based on previously developed information from which the location of the satellite can be predicted and, thus, limited to a small area of the sky, or cover a large area of the sky in accordance with a search routine. After the beacon of a satellite is acquired, the geographic area served by the satellite is determined. If the satellite does not serve the cell within which the ground terminal is located, a further satellite search is conducted, which may be based in part on information contained in the beacon of the acquired satellite. After the satellite serving the cell containing the ground terminal is acquired, a test is made to determine how long the satellite will continue to cover the cell.

Abstract: Methods are provided for accurate insertion of a constellation of satellites into a common orbit plane with a mean inclination .theta.. In an embodiment of the invention, an initial satellite is inserted on an initial insertion date and, for each of subsequent satellites, a respective orbit insertion date is selected. With reference to the latter date, the initial insertion RAAN is updated to find a current RAAN. This updating is accomplished with knowledge of a regression rate of the initial satellite's orbit normal about a Q vector. With reference to the Q vector's inertial position, an instantaneous inclination that corresponds to the mean inclination .theta. and the updated RAAN is then derived. Finally, the subsequent satellite is injected into an orbit having the instantaneous inclination and the current RAAN.

Abstract: A multiple altitude satellite relay system is disclosed in which Medium Earth Orbit satellites are continuously linked with at least one geosynchronous satellite to provide uninterrupted relaying of messages and data. The Medium Earth Orbit satellites are synchronized with the geosynchronous satellites to produce continuous links. A parameter to achieve the synchronization involves the positions of the Medium Earth Orbit satellite relays relative to the positions of the geosynchronous satellite relays. Another parameter to achieve synchronization involves the ratio between the orbital periods of the geosynchronous satellite relays relative to the orbital periods of the Medium Earth Orbit satellite relays. These parameters may be further adjusted to provide continuous links above the horizon of the earth.

Abstract: A system for acquiring the beacon of a satellite and synchronizing data transmission between the satellite and a ground terminal is disclosed. The ground terminal conducts a search for a satellite to be acquired. The search may be based on previously developed information from which the location of the satellite can be predicted and, thus, limited to a small area of the sky, or cover a large area of the sky in accordance with a search routine. After the beacon of a satellite is acquired, the geographic area served by the satellite is determined. If the satellite does not serve the cell within which the ground terminal is located, a further satellite search is conducted, which may be based in part on information contained in the beacon of the acquired satellite. After the satellite serving the cell containing the ground terminal is acquired, a test is made to determine how long the satellite will continue to cover the cell.

Abstract: A constellation (100) comprising a plurality of man-made satellites (1-27). The satellites (1-27) orbit a celestial body (110) along a plurality of orbits (120-128), which are located at a substantially common altitude and have a substantially common inclination. The satellites (1-27) are positioned in a predetermined order substantially along a wave (130). Each satellite (1-27) maintains its position in the predetermined order along the wave (130) while orbiting the celestial body (110). A system in accordance with the invention may further include a ground station adapted for enabling communication with at least one of the satellites (1-27). The satellites (1-27) may be positioned based on a Walker code T/P/F, where T is the total number of satellites (1-27) in a full Walker rosette corresponding to the Walker code, P is the number of distinct orbits (120-128), and F/T is the phase shift between adjacent orbits (120-128).

Abstract: The effect of the multipath distortions on the carrier phase measurements is reduced by using the weighted correlation functions. The generators of both periodic and dynamic weighted functions are used. The apparatus and method employing generators of such weighted functions can comprise the standard correlators and/or the weighted function correlators.

Abstract: A method and a system for locating ground equipment transmitting signals to a geostationary satellite, the method and the system being based on identifying the arrival directions of such signals within the coverage zone of the satellite. In the method, the arrival directions of the signals are identified by using a beam-forming active-module array antenna system on board the satellite, the system being controlled to define simultaneous beams in the radiation pattern of the antenna, the beams being superposed on one another with small offsets, the superposed beams corresponding to a limited analysis zone being illuminated within the coverage zone of the satellite, the system further being associated with a digital processing program which identifies the arrival directions of the signals which are received in the analysis zone.

Abstract: A method or system (10) includes test apparatus (14) for measuring the phase imbalance in a QPSK receiver (12). A signal generator (16) provides a test signal (18) to the receiver (12), which responsively generates I channel data (20) and Q channel data (22). The system includes an oversampler (26) for producing respective sets of oversampled I and Q channel data (24) and (25). A data processing system (28) cross-correlates the sets of I and Q channel data at each of a plurality of relative phase increments, and generates a plurality of cross-correlation energy values in response to said cross-correlation. The method or system determines the phase imbalance in response to at least a largest cross-correlation energy value of said plurality of cross-correlation energy values.

Abstract: An elliptical satellite system which carries out communication. The satellite orbits a height above the earth less than that necessary for geosynchronous orbits. When the satellite is near the apogee portion of its orbit, its velocity approximates the rotational velocity of the earth, and during that period it appears to hover over the earth. Each ground station on the earth always communicates with a satellite within a predetermined position of its apogee, and hence that satellite appears to the ground station to hover over the earth. The satellite hence does not communicate with any earth station when it is outside of that apogee portion. During the times when the satellite is outside the apogee portion, its communication is therefore shut off to prevent any possibility of interfering with geosynchronous satellites. During this time, the power supply on the satellite is also used to charge a battery on the satellite.

Abstract: A satellite attitude/orbit control system (300) for managing a satellite cluster (200) in a satellite constellation (207). A satellite cluster (200) comprises a master satellite (203) and secondary satellites (201, 202, 204, 204). The master satellite (203) receives sensor data from secondary satellites (201, 202, 204, 204) and combines such secondary sensor data with master sensor data from a master satellite (203) to calculate attitude/orbit estimates for all satellites within the satellite cluster (200). Attitude estimates are forwarded to each satellite for initiation of attitude/orbit control. Each satellite cluster (200) subordinates to a constellation master satellite (301) for receiving additional attitude/orbit estimates for use in determining and controlling satellite attitude/orbits.

Abstract: An elliptical orbit satellite system which describes communication and TT&C with ground stations. Earth stations are located for the circular orbiting satellite in a way such that the line of sight can never include geo synchronous satellites. The ground stations for the elliptically orbiting satellites monitor the position of the satellite, and no antenna communicates with a satellite which is in direct line of sight between the antenna and a geo satellite. Another aspect of the invention locates two TT&C stations, separated in longitude by 90.degree. and configures these stations such that each satellite in each constellation will be able to communicate with one of the two TT&C stations once during each satellite rotation period.

Abstract: A GPS reference system and corresponding method utilizing a network of reference stations and a master station. Each reference station receives GPS signals from GPS satellites it observes and computes in response a pseudo-range residual for each GPS satellite it observes. The master station is in communication with the reference stations to receive the computed pseudo-range residuals and comprises a pseudo-range residual synchronizer, an ephemeris and clock correction estimator for each GPS satellite observed by the reference stations, and a transmitter. The pseudo-range residual synchronizer is responsive to the received pseudo-range residuals in order to compute clock differences between the reference stations and remove the clock differences from the received pseudo-range residuals so as to synchronize them.

Abstract: A communication and position locating system (2) suitable for air traffic control is described. Multiple satellites (40) are provided in two geosynchronous constellations. One constellation (e.g., 4 satellites) has a first closed ground track (14). The other (e.g., 2 satellites (161, 182)) has a different ground track (18) or is geostationary, located outside of the first ground track (14). Geolocation information is transmitted by the satellites (40) to aircraft (28) and ground stations (26) so that aircraft (28) can determine their current position. A pseudo range correction map is provided to the aircraft (28) by the base stations (26) to permit differential geolocation measurements. The satellites (40) include communication transceivers (80) so that aircraft (28) can communicate voice and data to other aircraft (28) and to the ground stations (26, 30, 32) and automatically report their position to air traffic control centers (30), e.g., via the satellites (40).

Abstract: A satellite-based cellular telecommunications system employing a constellation of telecommunications satellites in medium earth orbit to provide multibeam radio frequency (rf) communications links for worldwide cellular telephone service with a minimum number of satellites. The telecommunications satellites are placed in a plurality of inclined orbits about the earth at an altitude of between approximately 5600 and 10,000 nautical miles. The characteristics of the orbits, such as the number of orbits, the inclination of each orbit, the number of satellites in each orbit and the altitude of the satellites, are tailored to maximize the coverage area of the satellites and their related line-of-sight elevation angles, while minimizing propagation time delays, the number of beam-to-beam and satellite-to-satellites handovers, and the total number of satellites.

Abstract: A system and method for maintaining a precise time standard among a system of orbiting satellites is disclosed. In an illustrative embodiment, atomic clock data is circulated among the satellites via RF crosslinks. Each satellite uses the received data as input to a Kalman process which acts to minimize the mean squared error among the satellite clocks to form a set of "ensemble clocks". The resulting ensemble clock values are then transmitted to an earth station where an offset between the ensemble clocks and Universal Time is computed. The offset is transmitted from the earth station to the satellites where it is used by the satellites to lock their on-board clocks to Universal Time, thereby creating a corrected system time. The corrected system time is transmitted, via RF crosslinks, to satellites not having operational on-board clocks. The satellites without atomic clocks employ phase locked loops to anchor their clocks to the corrected system time as it is received over the crosslinks.

Abstract: A satellite-based navigation system providing improved accuracy and reliability over wide geographical areas, including remote regions, is disclosed. Ranging-type signals transmitted through two or more commercial geostationary telecommunication satellites are received at known reference locations where navigation and correction information is generated and transmitted back to remote users. At the same time, the reference stations receive signals from the Global Positioning System (GPS), generate corrections for the GPS measurements, then transmit these corrections to the remote user. The remote user receives all of this information plus direct measurements from both the GPS and the geostationary satellites and, using conditional error processing techniques, provides a position solution whose accuracy and reliability exceeds that of GPS alone. Alternatively, integrated carrier phase data can be substituted for pseudoranges obtained from the geostationary satellite transmissions.