Patents

6,128,469
Satellite Communication System with a Sweeping High-Gain Antenna
The satellite communications system of this invention provides high-gain coverage to a wide geographic area with a minimum number of satellites. The satellites each include a high-gain antenna that periodically sweeps the satellite's service area to receive the messages from remote terminal units within the entire service area. In order to provide high gain, the antenna is designed to have a narrow beamwidth in at least one dimension. To cover the entire area, the antenna's field of view is swept across the entire service area. In the preferred embodiment, the antenna's field of view is essentially rectilinear, having a narrow beamwidth in one dimension and a beamwidth that extends across the entire service area in the other dimension, such that the sweeping effect is akin to that of a common push-broom. Because of the high gain of the satellite antenna, communications via the satellite can be accomplished using a low-gain wide-beamwidth antenna at the remote terminal unit.

6,396,819
Low-Cost Satellite Communication System
The satellite communication system has a ground station and multiple remote terminal units (RTUs). The RTUs are designed to infrequently transmit relatively short-duration messages and to repeatedly transmit the same message, so that it is received by a sweeping, high-gain satellite antenna. To minimize costs, the system is designed to allow the use of RTUs that use a fixed modulation scheme. Because the transmissions are infrequent and short, the loss of messages due to collisions is unlikely. As a further optimization, the RTUs have CDMA transmitters that each use the same CDMA code, and the ground station has multiple CDMA correlators using the same CDMA code. By using the same CDMA code, the loss of messages due to collisions is further reduced. For transmitting to the RTUs, the ground station has multiple CDMA modulators, each using a second CDMA code that is preferably orthogonal to the first CDMA code.

6,317,029
In Situ Remote Sensing
The in situ remote sensing system of this invention includes a plurality of sensors that are distributed about an area of interest, and the satellite communications system that receives communications signals from these sensors. The satellite communications system determines the location of each sensor at the time that the sensor transmits its communications signal, thereby facilitating the mapping of the value of the sensed parameter about the area of interest. In a preferred embodiment, the satellite communications system transmits a trigger signal to the sensors that are within the satellite antenna's field of view, and the sensors transmit only in response to the trigger signal. The sensors may be conventional active transmitters or passive transponders that receive their operating energy from a received trigger signal. The sensing devices within the sensor may also provide the operating energy for the sensor using, for example, photocells, piezoelectrics, and thermocouples.

6,296,205
RF Inspection Satellite
An inspection satellite is deployed in proximity to another satellite. The inspection satellite contains monitoring equipment and provides diagnostic information to an earth station to facilitate diagnosis of the other satellite and its equipment. The inspection satellite includes a flight control system that maintains the probe satellite in proximity to the satellite being monitored. In a preferred embodiment, the flight control system can also maintain the inspection satellite in an orbit about the satellite being monitored, to facilitate diagnostics based on patterns of signals. The monitoring equipment in a preferred embodiment for a transponder satellite includes an ability to monitor incoming signals and to compare the emissions from the satellite to them, to determine performance characteristics of the satellite equipment being monitored, such as phase shift and gain.

6,283,416
A Spacecraft Kernel
A spacecraft architecture is defined that distinguishes components and subsystems based on both functional and physical dependencies. On one side of the interface are kernel components that are both functionally and physically independent of the vehicle configuration and functionally and physically independent of the mission-specific system. On the other side of the interface are components that depend on either the spacecraft configuration or the mission-specific system. The kernel components can be included in a variety of spacecraft, independent of the spacecraft architecture and independent of the spacecraft mission. The kernel includes a communications system for communicating with an earth station, a command and data handling processor, and a power regulation and distribution system. The preferred kernel is extensible by allowing the selection of different capacity components within the kernel, each different capacity component utilizing the same standard interface for communicating with the vehicle and mission-specific components. By providing a standardized interface and extensible kernel, design changes do not propagate beyond the standardized interface, thereby substantially damping the costly ripple effect typically associated with changes that are introduced late in the design cycle.

6,286,787
Small Satellite GEO-to-Leo Orbit Transfer Vehicle
The excess space and weight capacity of a conventional geosynchronous-transfer launch vehicle is used to deploy satellites to a low-earth orbit (LEO). In a preferred embodiment, an orbit-transfer vehicle provides the navigation, propulsion, and control systems required to transport a payload satellite from a geosynchronous-transfer orbit (GTO) to a predetermined low-earth orbit. Upon entering low-earth orbit, the payload satellite is released from the orbit-transfer vehicle. To reduce the fuel requirements for this deployment via the orbit-transfer vehicle, a preferred embodiment includes aerobraking to bring the satellite into a low-earth orbit. In a preferred embodiment of this method of deployment, the provider of the orbit-transfer vehicle identifies and secures available excess capacity on geosynchronous-transfer launch vehicles, and allocates the excess capacity to the satellites requiring low-earth orbit deployment, thereby providing a deployment means that is virtually transparent to the purchaser of this deployment service.

6,561,461
Orbit Transfer Vehicle with Support Services
An orbit-transfer vehicle provides the navigation, propulsion, and control systems required to transport a payload satellite from a geosynchronous-transfer orbit (GTO) to a predetermined low-earth orbit (LEO). Upon entering low-earth orbit, the payload satellite is deployed from the orbit-transfer vehicle. To reduce the cost and complexity of the payload satellite, the orbit-transfer vehicle is configured to provide common functional services, such as communications and power regulation, to the payload satellite during the transport, and/or after deployment. To reduce the fuel requirements for this deployment via the orbit-transfer vehicle, a preferred embodiment includes aerobraking to bring the satellite into a low-earth orbit. In a preferred embodiment of this method of deployment, the provider of the orbit-transfer vehicle identifies and secures available excess capacity on launch vehicles, and allocates the excess capacity to the satellites requiring deployment, thereby providing a deployment means that is virtually transparent to the purchaser of this deployment service.

6,550,720
Aerobraking Orbit Transfer Vehicle
The excess space and weight capacity that is typical of a launch of large satellites to high-energy orbits, such as a geosynchronous orbit, is used to deploy small satellites at a substantially lower-energy orbit, such as a low-earth orbit. An orbit-transfer vehicle provides the navigation, propulsion, and control systems required to transport a payload satellite from a geosynchronous-transfer orbit (GTO) to a predetermined low-earth orbit (LEO). Depending upon the particular configuration, upon achieving the low-earth orbit, the orbit transfer vehicle either releases the payload satellite, or remains attached to the payload satellite to provide support services, such as power, communications, and navigation, to the payload satellite. To reduce the fuel requirements for this deployment via the orbit-transfer vehicle, the orbit-transfer vehicle employs aerobraking to bring the satellite into a low-earth orbit. The aerobraking is preferably performed at a nominal altitude of 150 km above the earth, where the atmosphere is dense enough to allow for a reasonably sized drogue device, yet rare enough to avoid the need for special purpose heat-shielding materials. In a preferred operation, the provider of the orbit-transfer vehicle identifies and secures available excess capacity on geosynchronous-transfer launch vehicles, and allocates the excess capacity to the satellites requiring low-earth orbit deployment, thereby providing a deployment means that is virtually transparent to the purchaser of this deployment service.

6,409,124
High-Energy to Low-Energy Orbit Transfer Vehicle
The excess space and weight capacity that is typical of a launch of large satellites to high-energy orbits, such as a geosynchronous orbit, is used to deploy small satellites at a substantially lower-energy orbit, such as a low-earth orbit. An orbit-transfer vehicle provides the navigation, propulsion, and control systems required to transport a payload satellite from a geosynchronous-transfer orbit (GTO) to a predetermined low-earth orbit (LEO). Depending upon the particular configuration, upon achieving the low-earth orbit, the orbit transfer vehicle either releases the payload satellite, or remains attached to the payload satellite to provide support services, such as power, communications, and navigation, to the payload satellite. To reduce the fuel requirements for this deployment via the orbit-transfer vehicle, the orbit-transfer vehicle employs aerobraking to bring the satellite into a low-earth orbit. The aerobraking is preferably performed at a nominal altitude of 150 km above the earth, where the atmosphere is dense enough to allow for a reasonably sized drogue device, yet rare enough to avoid the need for special purpose heat-shielding materials. In a preferred operation, the provider of the orbit-transfer vehicle identifies and secures available excess capacity on geosynchronous-transfer launch vehicles, and allocates the excess capacity to the satellites requiring low-earth orbit deployment, thereby providing a deployment means that is virtually transparent to the purchaser of this deployment service.