Hughes Electronics Corporation

The Boeing Company

Piyush R Shah

Douglas J Bender

David S Uetrecht

Garry Didinsky

Richard A Noyola

Thomas M Tanner

A system and method for determining the attitude in an inertial frame of a spacecraft spinning about an axis in a body frame including determining momentum vector direction in the inertial frame; determining momentum vector direction in the body frame; acquiring information from an at least single-axis sensor; obtaining reference information on the at least single-axis sensor; updating the attitude in the inertial reference frame using the momentum vector direction in the inertial frame, the momentum vector direction in the body frame, the output of the at least single-axis sensor, and the reference information on the at least single-axis sensor; and propagating the attitude using data from one or more inertial sensors.

Three-axis inertial attitude determination for spinning spacecraft

A system and method for acquiring the Earth by a three-axis stabilized spacecraft in the presence of a significantly time-varying Sun-Earth angle including obtaining an Earth cone described by rotating the nadir vector about the Sun vector, slewing the spacecraft about an axis until the Earth sensor boresight touches an edge of the Earth cone, updating the Earth cone due to the changing Sun-Earth separation angle, performing a spiral coning maneuver about the updated Earth cone until the Earth sensor detects the Earth, and locking onto the Earth so as to hold the Earth sensor boresight coincident with the nadir vector. Additionally, the spacecraft may be rotated about the nadir vector so as to bring the spacecraft into a desired final attitude.

Fuel and thermal optimal spiral earth acquisition

A system and method for acquiring Sun pointing in a three-axis stabilized spacecraft including slewing at least one solar wing until the Sun is detected, determining an initial Sun vector, performing one or more rotations of the spacecraft body so as to bring the instantaneous Sun vector coincident with a preferred final Sun vector, at least one rotation about an optimal axis, and slewing at least one solar wing to a preferred attitude relative to the Sun. In one embodiment, the optimal axis is chosen so as to minimize the time required to achieve an optimal thermal attitude. In another embodiment, the optimal axis is chosen so as to minimize the time required to align the instantaneous Sun vector with the final desired Sun vector. In a further embodiment, the optimal axis is chosen so as to maintain Earth lock.

Spacecraft acquisition of sun pointing

A system and method for slewing a spacecraft with a reaction wheel system including determining initial total momentum, determining maximum forward and reverse rates that can be realized within the reaction wheel system maximum storage capacity, determining a slew rate and slew direction from the maximum forward and reverse rates so as to minimize slew time for known slew angles or maximize slew rate for arbitrary slew angles, and slewing the spacecraft.

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Germantown, MD, United States of America

Piyush R Shah