Space Systems/loral, LLC

Cisco Technology, Inc.

Kam K Chan

Xen Price

Jeffery D Stoen

Xenophon H Price

Shoou Jiah Yiu

Ahmed A Kamel

Donald W Gamble

Tung Y Liu

Philip Conway Hirschberg

Mohammad Saghir Munir

Byoungsam Woo

Thomas Randolph

Mathew Lodge

Bruce Brumfield

George E White

Three-axis spacecraft momentum management is performed for a spacecraft traveling along a trajectory, by an actuator including at least one thruster disposed on a single positioning mechanism. As the spacecraft travels along the trajectory, a desired line of thrust undergoes a substantial rotation in inertial space. When the spacecraft is located at a first location on the trajectory, the single positioning mechanism orients the thruster so as to produce a first torque to manage stored momentum in at least one of a first and a second of the three inertial spacecraft axes. When the spacecraft is located at a second location on the trajectory, the single positioning mechanism orients the thruster so as to produce a second torque to manage stored momentum in at least a third of the three inertial spacecraft axes.

Spacecraft momentum management

Methods and apparatus for a spacecraft () orbiting about a celestial body such as the Earth to reacquire operational three-axis orientation with respect to that body. A method embodiment of the invention comprises determining () a set of actual conditions of the spacecraft, comprising a position of the spacecraft () in inertial space as a function of time and a set of angular rotation rates of the spacecraft () with respect to a coordinate frame of the spacecraft (), determining () an actual instantaneous direction of the sun with respect to the coordinate frame, and propagating () an estimated actual sun direction with respect to the coordinate frame as a function of time; determining () a desired sun direction with respect to the coordinate frame as a function of time; rotating () the spacecraft () and adjusting angular rotation rates of the spacecraft () so that an actual angle between the spacecraft () coordinate frame and the sun as a function of time substantially coincides with the desired sun direction with respect to the coordinate frame as a function of time; and, rotating () the spacecraft () around an axis defined by a line between the sun and the spacecraft until () the celestial body is observed by a celestial body sensor of the spacecraft.

Spacecraft three-axis attitude acquisition from sun direction measurement

A program and a method for a gateway are provided to deny incoming calls to prevent overload. The program provides a maximum CPU utilization threshold CPUT, which is set by the user. When a new incoming call is presented to the packet telephony gateway, the program checks a present CPU utilization CPUP. If the present CPU utilization CPUP is greater than the threshold, the call is refused. This insures that sound quality of the calls currently being handled is maintained, and that existing calls are never dropped.

Program and method for preventing overload in a packet telephony gateway

A method for inertially aligning a spacecraft along an axis, comprising the steps of using quaternion feedback control to reorient the spacecraft, and during the step of reorienting, using rate integrating gyroscopes in a pulse rebalance loop. The method operates to orient the spacecraft along an inertial direction of interest by the steps of operating a sensor to provide an initial fix on the inertial direction of interest; repetitively determining a difference between a commanded quaternion and a quaternion estimated based on sensed angular rates; and selectively applying torques to the spacecraft so as to drive the difference towards zero such that a spacecraft vector is aligned with the inertia direction of interest, thereby orienting the spacecraft. One mode of operation maintains the spacecraft fixed in orientation, while another mode of operation rotates the spacecraft about the direction of interest by using a bias-rate blind quaternion propagation technique.

Method to reorient a spacecraft using only initial single axis attitude

A spacecraft, such as a geosynchronous weather or communications satellite, is constructed to include a plurality of low thrust thrusters mounted at predetermined locations on at least one of a spacecraft appendage or a spacecraft bus. The plurality of low thrust thrusters are fired in pairs for at least one of removing a disturbance torque or providing fine pointing attitude control. In one embodiment the low thrust thrusters are mounted on a solar array panel, thereby increasing the moment arm and enhancing the thrust output of the low thrust thrusters. In one embodiment a spacecraft has a plurality of low thrust thrusters arranged as at least two sets of two low thrust thrusters, individual ones of the low thrust thrusters of a set being disposed in a V-configuration and mounted at predetermined locations on at least one of a spacecraft appendage or a spacecraft bus. The plurality of low thrust thrusters are selectively fired for achieving control of 3-axes of spacecraft attitude or momentum.

Spacecraft attitude control system using low thrust thrusters

A feedback motion compensation (FMC) component for use in a spacecraft having a payload. The FMC component includes a controller having sensor data inputs and an open loop dynamics model that is driven by actuator commands to produce a high accuracy attitude estimate suitable for payload motion compensation.

Autonomous spacecraft payload base motion estimation and correction

A method in accordance with this invention for maintaining a spacecraft in a desired orbital configuration, comprises the steps of: (a) recording a history of yaw momentum stored in momentum wheels; (b) estimating an average inertial torque and momentum over a previous time interval (such as one day); (c) determining a desired change in inertial torques using PID control law; (d) commanding a change in satellite trim tab and solar array position from a desired change in solar torque; and (e) slewing the trim tab and solar array a desired amount.

Autonomous solar torque management

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.

Method using double thruster firings to deadbeat flexible solar array

An attitude or orientation control system for spacecraft that provides for yaw axis error reduction and momentum dumping using a simple calculation involving only the momentum wheel speeds as input and which outputs two axis (roll and yaw) torque commands. The system utilizes the spacecraft 1) momentum wheels that store spacecraft momentum, 2) processing means for the calculation of control torques, and 3) torque actuators, e.g., magnetic torquers, that can provide a torque axis anywhere in the spacecraft roll/yaw plane, and involves three fundamental steps, 1) the input of the momentum wheel speed mearsurements, and 2) the calculation of the required torques, using the wheel speed measurements, and and 3) the outputting of the required torques in a form appropriate for controlling the available actuators.

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San Jose, CA, United States of America

Kam K Chan