摘要:
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.
摘要:
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.
摘要:
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.
摘要:
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. A central exclusion zone excludes all stars while a second or more exclusion zones allow some stars to be used in the attitude determination
摘要:
A system for counteracting a disturbance in a spacecraft includes a biasing apparatus that is coupled to the spacecraft and a spacecraft controller within the spacecraft. The disturbance has a known sign, magnitude and time. The biasing apparatus controls the biasing apparatus to place the spacecraft in a first dynamic state or position as a function of the sign, magnitude, and time of the disturbance. The controller also controls the spacecraft to a second dynamic state as a function of the known sign, magnitude, and time so that the spacecraft is oriented in a position other than the desired orientation so that after the disturbance the spacecraft is oriented in the desired orientation in response to the disturbance. The biasing apparatus may comprise a momentum wheel and the disturbance may comprise thrusting firing used for controlling momentum dumping.
摘要:
A laser crosslink attitude determination system using the payload laser crosslinks as the principal attitude sensor and thereby eliminating the need for additional high-cost, high performance dedicated celestial body or inertial sensors to provide attitude information. The method and system establishes optical crosslinks among orbiting spacecraft for attitude control by performing a series of deterministic scans. The need for separate dedicated attitude sensors is minimized or eliminated by increasing the acquisition field of uncertainty and/or reducing the crosslink acquisition field of view.
摘要:
Solar tabs are provided which have thermal emissivity and absorptivity properties designed to increase the attitude-control torques that can be generated with rotatable wings in a spacecraft. These increased torques enhance the ability to offset attitude-disturbance torques which typically tend to alter the attitude of a spacecraft from a desired attitude. The tabs include highly absorptive and nonemissive front faces, highly emissive back faces and a high thermal conductivity between the front faces and the back faces.
摘要:
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.
摘要:
Spacecraft cost, volume and weight are reduced with gyroscope calibration methods that can be effected with structures (e.g., a single-axis Sun sensor and a wheel system) which are typically carried by spacecraft for other purposes. In a method embodiment, these methods include an initial step 1) of calibrating a selected gyroscope and subsequent steps for each uncalibrated gyroscope of: 2) slewing the spacecraft by a slew angle and controlling attitude with the uncalibrated gyroscope for a selected time period to thereby couple its drift into the inertial axis of a calibrated gyroscope, 3) backslewing the spacecraft to return the calibrated gyroscope to its inertial axis, and 4) measuring an error angle generated by the uncalibrated gyroscope during the selected time period (e.g., with a Sun sensor or with the calibrated gyroscope). In another embodiment, steps 2-4 are replaced by steps of: 5) orienting a momentum vector to inhibit spacecraft rotation about an uncalibrated gyroscope's respective axis, and 6) calibrating the uncalibrated gyroscope from its output signal. Another method embodiment retains steps 5 and 6 but replaces the initial step 1) by repeating steps 5 and 6 with a different momentum vector. Drift components are thus sensed in two different spacecraft planes and these components are mathematically resolved to find gyroscope drifts.
摘要:
A method and system of orienting a payload of an orbiting spacecraft (14) to maintain a desired pointing profile in the presence of orbit inclination. A cone (12) is determined which is traced in inertial space by a pitch axis of the payload to maintain the desired pointing profile throughout an orbit. A bias momentum vector of the spacecraft (14) is oriented at an attitude which lies along the cone (12). The attitude has a nonzero angle with respect to a plane spanned by an orbit normal vector and an equatorial normal vector. The payload is rotated about a single body-fixed axis perpendicular to the pitch axis to align the pitch axis along the cone (12). As a result, the desired pointing profile is maintained throughout the inclined orbit.