Space Systems/loral, LLC

David Cielaszyk

Thomas J Holmes

Xen Price

Yassir Azziz

Matthew Machlis

Alicia Kavelaars

Rob Schwarz

Nobi Furumoto

Estimation of a desired antenna tracking profile is provided for a radio frequency autotracked (RFAT) antenna in the absence of a ground reference. A first RFAT antenna subsystem has a first antenna and a first antenna positioning mechanism (APM), each mounted on a vehicle, and a first ground-based RF beacon; a second RFAT antenna subsystem has a second antenna and a second APM, each mounted on the vehicle, and a second ground-based RF beacon. A controller stores an accumulated record of actuations of the second APM as a function of time under normal operation, calculates a desired antenna tracking profile for the second antenna, from a first ground-based RF beacon and from the accumulated record, excluding any real-time data from the second ground-based RF beacon, and transmits actuation commands to the second APM so as to cause the second antenna to track the desired antenna tracking profile.

Antenna tracking profile estimation

Apparatus and a method is presented for controlling yaw and roll excursions in a spacecraft having on-board components such as magnetic torquers, a roll thruster, momentum wheels, a wheel controller, an earth sensor, and a Digital Integrating Rate Assembly (DIRA). An observer module on the spacecraft receives inputs containing information comprising the unbiased roll error from the earth sensor, yaw momentum measured from the wheel speeds, and commanded yaw and pitch momentum output from the wheel controller, and produces therefrom output signals indicative of yaw estimate, yaw momentum estimate and torque disturbances estimate. A controller module on the spacecraft receives the output signals and combines them with inputs containing information comprising minimum yaw error and roll thrust yaw controller gain and minimum yaw error and roll thrust yaw momentum controller gain, and produces therefrom a signal for commanding the operation of the magnetic torquers to change roll momentum when within the dead band of the signal and, alternatively, for commanding the operation of both the magnetic torquers and the roll thruster to change roll momentum when the threshold of the dead band is exceeded. By so doing, the yaw attitude and yaw excursions are controlled.

Magnetic torquer control with thruster augmentation

A method for use in a spacecraft for controlling yaw angle deviations from a desired yaw angle profile. The method includes the steps of: (a) operating a profile generator to output roll angle, pitch angle, yaw momentum, and yaw angle profiles, the profiles being calculated to meet spacecraft pointing requirements while operating in an inclined orbit; (b) inputting to an observer raw roll-axis sensor measurements, commanded and measured yaw-axis wheel momentum storage, measured pitch-axis wheel momentum storage, and external roll-axis and yaw-axis torques, the observer generating a yaw angle estimate and a yaw momentum estimate; (c) subtracting the yaw angle profile from the yaw angle estimate to obtain a difference value; and (d) using the difference value and the yaw momentum estimate to control roll-axis thruster firings to limit spacecraft yaw angle deviations from the yaw angle profile.

Spacecraft yaw pointing for inclined orbits

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Longmont, CO, United States of America

David Cielaszyk