Abstract: According to an embodiment, a system includes a controller configured to determine a set of background light intensities associated with a satellite, where each background light intensity corresponds to at least one of an orientation and a position of a light source relative to the satellite, to determine a set of relative orientations of the light source corresponding to the set of background light intensities, and to generate an image of the satellite based, at least in part, on the determined set of background light intensities and the determined set of relative orientations of the light source.

Abstract: According to an embodiment, a system includes a controller configured to determine a set of background light intensities associated with a satellite, where each background light intensity corresponds to at least one of an orientation and a position of a light source relative to the satellite, to determine a set of relative orientations of the light source corresponding to the set of background light intensities, and to generate an image of the satellite based, at least in part, on the determined set of background light intensities and the determined set of relative orientations of the light source.

Abstract: Embodiments described herein provide for passive timing of asynchronous Inertial Measurement Unit (IMU) attitude data using information derived from a pattern of skipped and duplicate samples of attitude data generated by the IMU. One embodiment is an attitude controller for a vehicle that generates samples of attitude data at a first frequency (f1) from an IMU of the vehicle. The IMU updates the attitude data at a second frequency (f2). Each update of the attitude data includes a time stamp. The attitude controller is processes time stamps in the samples to identify a pattern of at least one of a skipped sample of an update to the attitude data and a duplicate sample of an update to the attitude data. The attitude controller estimates lag times between updates of the attitude data and samples of the attitude data based on the pattern and a relationship between f1 and f2.

Abstract: Embodiments described herein provide for passive timing of asynchronous Inertial Measurement Unit (IMU) attitude data using information derived from a pattern of skipped and duplicate samples of attitude data generated by the IMU. One embodiment is an attitude controller for a vehicle that generates samples of attitude data at a first frequency (f1) from an IMU of the vehicle. The IMU updates the attitude data at a second frequency (f2). Each update of the attitude data includes a time stamp. The attitude controller is processes time stamps in the samples to identify a pattern of at least one of a skipped sample of an update to the attitude data and a duplicate sample of an update to the attitude data. The attitude controller estimates lag times between updates of the attitude data and samples of the attitude data based on the pattern and a relationship between f1 and f2.

Abstract: In an exemplary embodiment, a pattern is recognized from digitized images. A first image metric is computed from a first digitized image and a second image metric is computed from a second digitized image. A composite image metric is computed as a function of the first image metric and the second image metric, and a pattern is identified by comparing the composite image metric against a reference image metric. The function may be a simple average or a weighted average. The image metric may include a separation distance between features, or a measured area of a feature, or a central angle between two arcs joining a feature to two other features, or an area of a polygon whose vertices are defined by features, or a second moment of a polygon whose vertices are defined by features. The images may include without limitation images of friction ridges, irises, or stars.

Abstract: A method for controlling an actuator of a vehicle comprises providing a dynamic condition sensor generating a vehicle movement signal and a position sensor for generating a reported position. A processor is coupled to the inertial sensor and the position sensor and comprises an estimator, a position measurement predictor having a filter, a comparator and a control shaping block, said estimator generating a vehicle position based upon the dynamic condition sensor, said position measurement predictor generating an estimated position measurement in response to the reported vehicle position and a matched frequency response to the movement signal, said control shaping block generating an actuator control signal in response to a comparison of the estimated position measurement and the reported vehicle position.

Abstract: In an exemplary embodiment, a pattern is recognized from digitized images. A first image metric is computed from a first digitized image and a second image metric is computed from a second digitized image. A composite image metric is computed as a function of the first image metric and the second image metric, and a pattern is identified by comparing the composite image metric against a reference image metric. The function may be a simple average or a weighted average. The image metric may include a separation distance between features, or a measured area of a feature, or a central angle between two arcs joining a feature to two other features, or an area of a polygon whose vertices are defined by features, or a second moment of a polygon whose vertices are defined by features. The images may include without limitation images of friction ridges, irises, or stars.

Abstract: A method for controlling an actuator of a vehicle comprises providing a dynamic condition sensor generating a vehicle movement signal and a position sensor for generating a reported position. A processor is coupled to the inertial sensor and the position sensor and comprises an estimator, a position measurement predictor having a filter, a comparator and a control shaping block, said estimator generating a vehicle position based upon the dynamic condition sensor, said position measurement predictor generating an estimated position measurement in response to the reported vehicle position and a matched frequency response to the movement signal, said control shaping block generating an actuator control signal in response to a comparison of the estimated position measurement and the reported vehicle position.

Abstract: A system (18) includes: a) A vehicle (12) includes an attitude or angular velocity control system (38), a plurality of star trackers or star sensors (22) each having a field of view (28); b) a memory (30) having a star catalog (32), a star pair catalog (58) and a reference table (56) stored therein; and c) a processor (24) coupled to the attitude or angular velocity control system (38), the star trackers or star sensors (22), and the memory (30). The processor (24) determines the vehicle inertial attitude or angular velocity or sensor alignment, based, in part, on the star pair catalog (58) and reference table (56). The design of the star pair catalog (58) and reference table (56) is suitable for rapid determination of attitude or angular velocity or sensor alignment, and an efficient use of memory.

Abstract: A method and apparatus for correcting a beam error is disclosed. One embodiment of the method comprises the steps of selecting beamweight coefficients based on the satellite orbital data, evaluating an effect of quantization of the beamweight coefficients on the beam error, and selecting beamweight coefficients based at least in part upon the evaluation of the effect of beamweight coefficient quantization on beam error. One embodiment of the apparatus comprises a beamweight correction module for selecting beamweight coefficients based on satellite orbital data, for evaluating the effect of quantization of the beamweight coefficients on beam error, and for selecting beamweight coefficients based at least in part upon the evaluation of the effect of beamweight coefficient quantization on beam error. The beamweight correction module comprises a beamweight generator and a beamweight quantizer for quantizing beamweights from the beamweight generator.

Abstract: A method of correcting for beacon pointing errors is disclosed. A desired beacon value and a predicted measured beacon value are computed and used to generate the beacon correction. An antenna pattern calculator can be used to compute the predicted measured beacon value, and a beacon correction value generator can be used to compute the desired beacon value and to generate the beacon correction.

Abstract: A method and apparatus for reducing centroiding error of a star sensor having a plurality of pixels is disclosed. The method comprises the steps of computing a star sensor angular slew rate of ? pixels per star sensor integration period ?, collecting star sensor data while slewing the star sensor according to the selected star sensor angular slew rate ?, and filtering the collected star sensor data according to a frequency determined by the selected star sensor angular slew rate.

Abstract: A method and apparatus for reducing centroiding error of a star sensor having a plurality of pixels is disclosed. The method comprises the steps of computing a star sensor angular slew rate of ? pixels per star sensor integration period ?, collecting star sensor data while slewing the star sensor according to the selected star sensor angular slew rate ?, and filtering the collected star sensor data according to a frequency determined by the selected star sensor angular slew rate.

Abstract: A vehicle (12) including a control system (18) is used for controlling vehicle attitude or angular velocity (38). The processor (24) is coupled to a star sensor or tracker (22) and a memory (30) that may include a star catalog (32), and an exclusion list (36). The exclusion list (36), a list of stars to be temporarily excluded from consideration when determining attitude or angular velocity or relative alignment of star sensors or trackers, is calculated on board. Such a calculation prevents the necessity for a costly, periodic, ground calculation and upload of such data. By manipulating the star catalog, or sub-catalogs derived from said catalog, based upon the exclusion list (36), measurements of such excluded stars are prevented from corrupting the attitude or angular velocity or alignment estimates formulated on board. The system uses multiple stayout zones for excluding stars from the exclusion list.

Abstract: A vehicle (12) including a control system (18) is used for controlling vehicle attitude or angular velocity (38). The processor (24) is coupled to a star sensor or tracker (22) and a memory (30) that may include a star catalog (32), and an exclusion list (36). The exclusion list (36), a list of stars to be temporarily excluded from consideration when determining attitude or angular velocity or relative alignment of star sensors or trackers, is calculated on-board. Such a calculation prevents the necessity for a costly, periodic, ground calculation and upload of such data. By manipulating the star catalog, or sub-catalogs derived from said catalog, based upon the exclusion list (36), measurements of such excluded stars are prevented from corrupting the attitude or angular velocity or alignment estimates formulated on board.

Abstract: A method and apparatus for filtering sensor measurements is disclosed. The method comprises the steps of digitally integrating the sensor measurements at a first processing rate to produce a first intermediate signal, digitally integrating the first intermediate signal at the first processing rate to produce a second intermediate signal, sampling the second intermediate signal at a second processing rate to produce a third intermediate signal, digitally differentiating the third intermediate signal at the second processing rate to produce a fourth intermediate signal, and digitally differentiating the fourth intermediate signal at the second processing rate to produce filtered sensor measurements.

Abstract: A system (18) includes: a) A vehicle (12) includes an attitude or angular velocity control system (38), a plurality of star trackers or star sensors (22) each having a field of view (28); b) a memory (30) having a star catalog (32), an allocated area for a star pair catalog (58) and a reference table (56) stored therein; and c) a processor (24) coupled to the attitude or angular velocity control system (38), the star trackers or star sensors (22), and the memory (30). The processor (24) populates the star pair catalog (58), using the method described herein. The processor (24) then periodically determines the vehicle inertial attitude or angular velocity or sensor alignment, based, in part, on the star pair catalog (58) and reference table (56). The novel ability of the software to autonomously populate the star pair catalog (58) allows users to avoid uploading a large amount of data, and the problems associated with such an upload.

Abstract: A method and an apparatus for controlling the attitude and momentum of a spacecraft while deploying an appendage from the spacecraft. The method uses solar tacking and similar techniques to produce differential solar torques that are used to control the momentum and attitude of the spacecraft during the appendage deployment.

Abstract: A method and an apparatus for controlling the attitude and momentum of a spacecraft while deploying an appendage from the spacecraft. The method comprises the steps of predicting an environmental torque the spacecraft will be subjected to during deployment of the appendage, computing a magnitude and a direction of momentum to add to the spacecraft to at least partially oppose the predicted environmental torque, and storing the computed magnitude and direction of momentum in at least one of the momentum wheels before deploying the appendage.

Abstract: A system and method for performing in-orbit alignment calibration using on-board attitude sensors to improve reflector alignment after deployment to improve spacecraft pointing.