The Boeing Company

Hughes Electronics Corporation

Yeong-Wei Andy Wu

Rongsheng Li

David D Needelman

Richard A Fowell

Ketao Liu

Yong Liu

Peter C Lai

Garry Didinsky

Hanching Grant Wang

Richard Yining Chiang

Douglas H Hein

William L Burkett, Jr

Christopher L Rice

Jeffrey L Lee

Bruce N Eyerly

Che-Hang Charles Ih

David S Uetrecht

Grant Wang

Jeffrey A Kurland

David L Augenstein

Umesh S Ketkar

Jonathan French

Salma I Saeed

Alec M Dawson

James H Green

James P Alstad

Method and system for determining a point-ahead angle from a first spacecraft to a second spacecraft, each spacecraft having a laser communication ('lasercom') terminal is provided If ephemeris data regarding the second spacecraft is unavailable to the first spacecraft while the second spacecraft is mobile, (a) obtaining attitude information regarding the first spacecraft; and (b) obtaining gimbal offload commands from a fast steering mirror and a first spacecraft telescope subsystem of the first spacecraft; wherein a point-ahead determination module receives the attitude information and the gimbal offload commands; and determining an estimate of the point-ahead angle from the first spacecraft to the second spacecraft based on the attitude information and the gimbal offload commands.

Method and system for laser based communication

A method of estimating the alignment of a star sensor () for a vehicle () includes generating star tracker data. A vehicle attitude and a star sensor attitude are determined in response to the star tracker data. A current alignment sample is generated in response to the vehicle attitude and the star sensor attitude. A current refined estimate alignment signal is generated in response to the current alignment sample and a previously refined estimate alignment signal via a vehicle on-board filter ().

Real-time refinement method of spacecraft star tracker alignment estimates

In accordance with an embodiment of the present invention, a resolver system has at least one resolver and at least one amplifier in electrical communication with each resolver. A reference circuit is in electrical communication with the amplifiers. The reference circuit provides reference signals to the amplifiers. A non-linearity calibration and compensation circuit in communication with each amplifier uses the amplified reference signals to provide scale factors, so as to enhance a precision of the resolver system.

Scale factor calibration and compensation for angular position resolver

A method and apparatus for determining the attitude of a satellite using crosslink information is disclosed. The method and apparatus integrates data from the crosslinks with data available from other sources including, for example, star sensors, inertial sensors, and earth limb sensors to derive an accurate estimate of the satellite attitude, even in harsh nuclear environments.

Method and apparatus for determining a satellite attitude using crosslink reference signals

Methods, systems and devices are disclosed for positioning an antenna having a sub-reflector assembly. A conical scan processor receives a period for a reference time pulse and a time tag. The processor calculates a rotation angle of the sub-reflector assembly using the received period for the reference time pulse and the received time tag. The processor may also receive a power measurement associated with the time tag. The processor may calculate and then output antenna boresight errors based on the calculated rotation angle of the sub-reflector assembly and the power measurements associated with the time tag.

Method and apparatus for precision antenna boresight error estimates

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.

Method for compensating star motion induced error in a stellar inertial attitude determination system

A method, apparatus, article of manufacture, and a memory structure for designing a robust controller. The method comprises the steps of determining a plant model G of the system dynamics; bounding system dynamics unmodeled by the plant model G of the system dynamics by a weighting function W; applying a transform to an augmented plant model T having the plant model G and the weighting function W; defining a controller {tilde over (F)} from the transformed plant model T; and applying an inverse of the transform to the controller {tilde over (F)} defined from the transformed plant model and the weighting function W to generate the robust controller F.

Robust spacecraft controller and method for designing same

An airborne radio frequency (RF) antenna terminal system includes a two-axis gimbals control system and a phased array antenna. The phased array antenna electronically steers the receive and transmit beams using phase shifters. The electronically steered beams provide a virtual third-axis for the two-axis gimbals control system. The combination of the electronically steered beams and the two-axis gimbaled system provides accurate beam steering for the keyhole region of the two-axis gimbals control system so that the RF communication link is prevented from being lost in the keyhole region.

Electronic beam steering for keyhole avoidance

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

Fast access, low memory, pair catalog

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 &#x3c9; pixels per star sensor integration period &#x3c4;, collecting star sensor data while slewing the star sensor according to the selected star sensor angular slew rate &#x3c9;, and filtering the collected star sensor data according to a frequency determined by the selected star sensor angular slew rate.

Pixel-frequency slews and filters for star data measurements

Time-of-day tracking with INS input is described. In one embodiment, a range rate and a range acceleration is generated from inertial navigation system data received from a moveable platform (e.g. an airborne platform). A time and frequency estimation filter receives the range rate, the range acceleration and a timing-based error signal from a time discriminator, and can then generate a time-of-day correction signal and a frequency correction signal. A time-of-day generator receives the time-of-day correction signal and generates a time-of-day correction, and a clock frequency generator receives the frequency correction signal and generates a frequency correction. The time discriminator receives a satellite synchronization signal from a satellite, the time-of-day correction from the time-of-day generator, and the frequency correction from the clock frequency generator. The time discriminator initially generates the timing-based error signal from the satellite synchronization signal, and subsequently generates the timing-based error signal from the time-of-day correction and the frequency correction to synchronize the satellite with the moveable platform.

Time-of-day tracking with INS input

A vehicle () including a control system () is used for controlling vehicle attitude or angular velocity (). The processor () is coupled to a star sensor or tracker () and a memory () that may include a star catalog (), and an exclusion list (). The exclusion list (), 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 (), 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. A central exclusion zone excludes all stars while a second or more exclusion zones allow some stars to be used in the attitude determination

Multiple stayout zones for ground-based bright object exclusion

A vehicle () including a control system () is used for controlling vehicle attitude or angular velocity (). The processor () is coupled to a star sensor or tracker () and a memory () that may include a star catalog (), and an exclusion list (). The exclusion list (), 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 (), measurements of such excluded stars are prevented from corrupting the attitude or angular velocity or alignment estimates formulated on board.

Method and apparatus for real-time star exclusion from a database

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

Growing community of inventors

Rancho Palos Verdes, CA, United States of America

Yeong-Wei Andy Wu