Abstract: An onboard star tracking system is used to provide continuous attitude and orbital position data independent of the image generating instruments. Such data is instantaneously and continually supplied to the onboard computer which translates such information into mirror position coordinates which is added to the mirror position set based on estimated data from the ground control. An error signal is generated which is used to further adjust the position of the mirror.

Abstract: A method and an apparatus for a multibeam phased array antenna transmission based on heterodyning to produce the RF transmission signals with appropriate phase shift and thereby reducing the effect of certain space constraints in the confined area of the transmitter as higher and higher frequencies of transmission are employed. In the present invention, RF signals at an intermediate frequency, not the ultimate frequency of transmission, comprise the signal frequencies of a beam forming network which provides input to a multiplexed power divider. The power divider outputs the phase shifted signals to an input at each of a number of multiplexed combiners. The output of each combiner is fed to a mixing device which then shifts the input frequency to a higher frequency, using an appropriate local oscillator signal. The mixer outputs are coupled to separate power amplifiers, whose outputs are fed to the elemental radiators.

Abstract: The invention relates to a Common Direct Broadcasting Service (CDBS) system for a communications spacecraft. The CDBS system comprises N uplink antennas for receiving uplinks from terrestrial transmitting stations. Each uplink includes left-hand circular polarized (LHCP) signals and/or right-hand circular polarized (RHCP) signals. The LHCP signals and the RHCP signals have frequencies within predetermined channels of a first and/or second predefined frequency band. The CDBS system also comprises means for separating the LHCP signals of the uplinks received by each uplink antenna from the RHCP signals of the uplinks received by each uplink antenna. The CDBS system further comprises a plurality of receivers for converting the separated LHCP signals and RHCP signals of the uplinks to first signals and second signals, respectively, of the uplinks. The first and second signals have frequencies within channels of a third and/or fourth predefined frequency band.

Abstract: A broadband linearizer for use with a power amplifier. The broadband linearizer includes a broadband linearizer bridge, a preamplifier/attenuator, a post amplifier/attenuator, and a control circuit. The broadband linearizer bridge includes a power divider and a power combiner interconnected by linear and nonlinear arms. The linear arm has a phase shifter, a passive equalizer, and a first delay line that are serially coupled together. The nonlinear arm has a distortion generator, an attenuator and a second delay line that are serially coupled together. The control circuit controls respective settings of the broadband linearizer bridge, preamplifier/attenuator and post amplifier/attenuator. The control circuit provides bias circuitry and sends command and telemetry signals to control operation of the broadband linearizer. The broadband linearizer provides for independent, flexible gain and phase control that can mate with different kinds of power amplifiers having various gain and phase performance.

Abstract: A precise, spacecraft camera image navigation and registration system and method wherein a computer 36 on-board the spacecraft and a ground system comprising at least two ground stations precisely compute image navigation and registration data from precise data measurements. The computer on-board the spacecraft (spacecraft control system) uses precise star tracker, gyro, and earth sensor attitude data to precisely point the spacecraft and the camera. The ground system utilizes precise star measurement data from the camera and range data from the ground stations time tagged with GPS precise clock data. The ground system uses these precise measurements to determine precise orbit and attitude coefficients and uploads these coefficient to the spacecraft. The computer on-board the spacecraft uses these precise coefficients to generate and apply precise signals to compensate for slow orbit and attitude variations and register camera images in real time.

Abstract: A battery system for an body stabilized satellite traveling in a geosynchronous orbit comprises east and second battery modules and similarly facing radiators for discharging beat to deep space. Heat conduction arteries connect each battery module to its associated radiator. An east thermal switch is operable for thermally connecting the first battery module to and from the east facing radiator. Similarly, a west thermal switch is operable for thermally connecting the second battery module to and from the west facing radiator. A computer selectively operates the east and west thermal switches such that, in one instance, for a time between the satellite's emergence from the earth's shadow and its position nearest the sun, the respective thermal switches thermally connect the first battery module to its radiator while thermally disconnecting the second battery module from its radiator.

Abstract: A spacecraft includes a plurality of thrusters mounted at predetermined locations on a spacecraft structure, individual ones the plurality of thrusters being fired for generating a torque about a desired axis. The firing of a thruster is partitioned into two firings that are offset in time by an amount .DELTA.t, wherein .DELTA.t=(1/2).times.(1/F).times.SF, where F is a dominant modal frequency, in Hertz, for any particular axis (nominally the 1st mode) of the spacecraft structure, and where SF is a scale factor that is adjustable about the frequency. In a presently preferred embodiment the thruster is a low thrust thruster that is mounted on a solar array panel, and the thrusters are fired in pairs.

Abstract: A very large number of small electric cells are assembled electrically in parallel into a cell module to provide a large ampere-hour capacity and, in turn, multiple cell modules are series connected into a spacecraft battery having the power necessary to satisfy the requirement of the spacecraft. The invention provides for (a) three-dimensional packaging of parallel cells, (b) rejecting the internal heat from such a package, and (c) providing redundant electrical fuse protection for the internal cell array. Thus, at least first and second layers are provided, each being of plural commonly aligned, parallel bussed, electric cells, each cell including opposed ends and an outer peripheral surface. The cells are disposed in a planar side-by-side relationship, and each layer includes a plurality of outermost cells encompassing an interior region. The layers are connected electrically in parallel and are laterally coextensive and aligned in an end-to-end relationship.

Abstract: An antenna, forming a part of an antenna system, is suitable for use on a communication satellite encircling the earth, and has a reflector illuminated by a set of feed elements wherein one of the feed elements generates a primary beam. The reflector is shaped to establish a specific configuration of the beam, and, upon illumination of the earth, there results a specific shape to the beam footprint. A mechanical positioning device connects the antenna with a body of the spacecraft for adjusting an orientation of the feed antenna and its beam relative to the body of the spacecraft. Control circuitry for adjustment of signal strengths and phase shifts of signals sent to respective ones of the feeds is accomplished by electronic circuitry including a memory which stores coefficients employed in the operation of variable power dividers and variable phase shifters of a feed network supplying electromagnetic signals to the feed.

Abstract: For a switching of a magnitude of system gain in the driving of a load by a control system, a method of inhibiting formation of switching transients has a step of distinguishing between an estimate of a plant state, such as the attitude of a spacecraft, and an integral control state which allows the control system to provide actuation in response to long term disturbances, such as solar pressure, in operation of the system. In the case of a feedback configuration to the system with controller in a forward branch and an estimator in a feedback branch, a loop error signal serves to drive an actuator of the load via the controller. The method includes a further step of evaluating a portion of a controller input signal which is exclusive of an integral control state and which comprises a difference between a desired state and an estimate of the plant state.

Abstract: An antenna is shaped to provide a predetermined contour and is mounted for universal movement on its support. An electronically controlled drive mechanism is operatively associated with the antenna to rotate the antenna to preselected positions corresponding to specific target locations. A fixed feed horn excites the antenna to generate a first radiation pattern which conforms to the shape of a primary desired target location when the antenna is moved to a first position and a second radiation pattern which conforms to the shape of a secondary desired target location when the antenna is moved to a second position. By further designing the antenna shape, multiple contoured beams for multiple target locations are obtained.

Abstract: A technique of operating a lithium-ion (Li-ion) battery is proposed for maximizing battery life. In a first instance, this technique calls for charging the battery at a lower temperature than the temperature at which discharge begins. Preferably, the battery is charged at a temperature T.sub.1 in the range between about +5.degree. C. and -20.degree. C.; and discharged at a temperature T.sub.2, in the range of about +5.degree. C. to +30.degree. C., T.sub.2 being higher than T.sub.1. In another instance proposed by the invention, the battery is charged to an elevated state of charge which is above an initial state of charge at a temperature T.sub.1 between about +5.degree. C. and -20.degree. C. which is lower than a temperature T.sub.2, in the range of about +5.degree. C. to +30.degree. C., at which discharge begins.

Abstract: A system and method for RF autotracking multiple antennas to compensate for disturbances experienced by the antennas. The system and method uses two control algorithms implemented in fast and slow controllers and sums the result for each antenna that is tracked. One (fast) control algorithm corrects for rapid, common mode disturbances such as spacecraft motion disturbances, while the other (slow) control algorithm corrects for slower disturbances, such as thermal distortion, that do not affect all antennas in the same manner.

Abstract: RF signal nulling and loss of RF lock (i.e., loss of a communications or command link) is resolved by changing the phase of signals derived from first and second (+Z and -Z) antennas so that they add in phase instead of canceling. This is accomplished automatically by using a computer or processor to measure the RF signal level output by a receiver and change the phase of the incoming signal using a phase shifter to achieve the highest level. A squelch circuit in the receiver is used to determine the maximum obtainable RF signal level. The squelch level is compared in a computer to a threshold when the system looks for a higher squelch level. The phase of the phase shifter is changed using a computer to maximize the received signal level. A feedback loop from the receiver through the computer to the phase shifter provides a path to shift the phase of the incoming RF signal in one of the paths so the respective signals add instead of cancel, which eliminates the signal nulling problem.

Abstract: A wireless telephone system (10) capable of servicing a roaming wireless telephone user (30) includes a satellite (22) communications system consisting of at least one orbiting satellite (22); at least one terrestrial-based gateway (12, 14, 16, 18) having access to a database (20) of users, destination codes (telephone numbers); at least one network coordinating gateway (28) within at least one satellite service area (24); a single network control center (25); and a plurality of terrestrial communications links (e.g. 101). The system (10) operates by effecting communication between a terrestrial wireless telephone end user transceiver apparatus (e.g. 501) and a terrestrial communications link (e.g. 101) via a single relay through a single satellite (22) or a succession of single relay satellites (22) wherein the relay station may be in motion relative to the end user transceiver apparatus (501) and the terrestrial communications link (101).

Abstract: An antenna element and beamforming network (10) preferably comprises a plurality of radiators (12), a plurality of band pass filters (14) and a plurality of test couplers (16). Each radiator (12) is coupled to a dedicated MMIC (18). The output of MMICs (18) are coupled to a power stripline combiner (20) to provide a single output. Each of MMICs (18) is independently controllable to shape the antenna beams as desired for producing nulls in pattern coverage. The output of stripline combiner (20) may also be coupled through an output test coupler (46) to a jammer detector and correlator (24). In one embodiment, radiators (12) are horns that include filters (14). The output of each horn is coupled to the input of its dedicated MMIC (18). In another embodiment, radiators (12) are a patch array coupled together by a stripline combiner. The output of the stripline combiner is coupled by band pass filter (14) to the input of the respective MMICs (18).

Abstract: A wireless telephone system capable of servicing a roaming wireless telephone user includes a satellite communications system consisting of one or more orbiting satellites, each carrying a database of users, destination codes and call codes, within a satellite service area, a satellite control center, and a plurality of terrestrial communications links.

Abstract: The system consists of a satellite position and attitude reference system utilizing Global Positioning System data, an on board computer to analyze and generate position and attitude dependent instructions, an attitude control system to adjust the attitude of the space craft in response to instructions from the computer, an imaging system responsive to the computer to generate image data and transmit it, and a ground based, image data receiver and post processing system to assemble the image data, code the data and compile sequential images into a mosaic depicting the target. The on board computer delays the generation of attitude control instructions, during the process of capturing image data, in order to avoid image distortion due to attitude adjustment movement of the spacecraft.

Abstract: When the cell of a battery, most notably a lithium ion battery, fails and human intervention is unavailable to correct the problem. a system is provided for optimizing the energy storage capacity of the battery. At least two cellular strings, each including a plurality of battery cells, are connected electrically in series. All cellular strings contain the same number of battery cells and are electrically connected in parallel to form a battery array powering a load. A sensor detects the condition of each battery cell and sends a signal of the detected condition to a controller for operating the battery array for powering the load. A switching arrangement is responsive to the sensor, upon failure of a battery cell in one cellular string, for disconnecting at least one other battery cell of the battery array such that, thereafter, the modified battery array continues to power the load with reduced but optimized capacity.

Abstract: An electromagnetic wave propagation structure, suitable for the transmission of an electromagnetic wave and the formation of resonators within filters, is constructed of both high and low dielectric-constant materials wherein the high dielectric-constant is in excess of approximately 80 and the low dielectric-constant is less than approximately 2. A boundary between the high and the low dielectric-constant materials serves as an electric wall to waves propagating in the low dielectric-constant material and as a magnetic wall to waves propagating in the high dielectric-constant material. This permits substitution of the high dielectric-constant material for metal elements, such as resonators and feed structures in filters. Furthermore, the use of a cladding of dielectric material of one of the foregoing dielectric ranges about a core of material of the other of the foregoing dielectric ranges enables construction of waveguides having rectangular and circular cross-sections.