초록 ▼

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 i

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.

대표청구항 ▼

1. A method for managing momentum of a spacecraft traveling along a trajectory, the method comprising: determining a respective momentum storage error (MSE) in each of three inertial spacecraft axes, said respective MSE comprising a difference, for each axis, between a momentum value actually stored

1. A method for managing momentum of a spacecraft traveling along a trajectory, the method comprising: determining a respective momentum storage error (MSE) in each of three inertial spacecraft axes, said respective MSE comprising a difference, for each axis, between a momentum value actually stored on the spacecraft and a desired momentum value;reducing each respective MSE by producing, with at least one thruster disposed on a single positioning mechanism, a plurality of torques, by: orienting the thruster, with the single positioning mechanism, so as to produce a first torque that reduces the respective MSE of either or both of a first and a second of the three inertial spacecraft axes when the spacecraft is located at a first location on the trajectory, and,orienting the thruster, with the single positioning mechanism, so as to produce a second torque that reduces the respective MSE of at least a third of the three inertial spacecraft axes when the spacecraft is located at a second location on the trajectory; wherein,the single positioning mechanism is configured to orient the thruster so as to simultaneously (i) accelerate the spacecraft along a line of thrust and (ii) produce a torque around at least one of two axes substantially orthogonal to the nominal thrust vector; andas the spacecraft travels along the trajectory, a desired line of thrust undergoes a substantial rotation in inertial space. 2. The method as recited in claim 1, wherein spacecraft acceleration and MSE are simultaneously controlled by the at least one thruster disposed on the single positioning mechanism. 3. The method as recited in claim 1, wherein the thruster is a low thrust electric propulsion device. 4. The method as recited in claim 3, wherein the thruster is a Hall effect thruster. 5. The method as recited in claim 1, wherein, as the spacecraft travels along the trajectory, the substantial rotation is approximately ninety degrees. 6. The method as recited in claim 1, wherein the single positioning mechanism has two degrees of freedom. 7. A spacecraft comprising: at least one thruster;spacecraft control electronics configured to: (i) generate a desired orbit transfer profile for the spacecraft; and(ii) determine a respective momentum storage error (MSE) in each of three inertial spacecraft axes, said respective MSE comprising a difference, for each axis, between a momentum value actually stored on the spacecraft and a desired momentum value; anda spacecraft steering apparatus, comprising the at least one thruster disposed on a single positioning mechanism, that, responsive to signals from the spacecraft control electronics: controls the attitude of the satellite so as to follow the desired orbit transfer profile; andreduces each respective MSE by producing, with the at least one thruster, a plurality of torques, by: orienting the thruster, with the single positioning mechanism, so as to produce a first torque that reduces the respective MSE of either or both of a first and a second of the three inertial spacecraft axes when the spacecraft is located at a first location on the trajectory, and,orienting the thruster, with the single positioning mechanism, so as to produce a second torque that reduces the respective MSE of at least a third of the three inertial spacecraft axes when the spacecraft is located at a second location on the trajectory; wherein, the single positioning mechanism is configured to orient the thruster so as to simultaneously (i) accelerate the spacecraft along a line of thrust and (ii) produce a torque around at least one of two axes substantially orthogonal to the nominal thrust vector; andas the spacecraft travels along the trajectory, a desired line of thrust undergoes a substantial rotation in inertial space. 8. The spacecraft as recited in claim 7 wherein the at least one thruster comprises an electric propulsion thrusters. 9. The spacecraft as recited in claim 8 wherein the at least one thruster comprises a Hall effect thruster. 10. The spacecraft as recited in claim 7, wherein, as the spacecraft travels along the trajectory, the substantial rotation is approximately ninety degrees. 11. The spacecraft as recited in claim 7 wherein the spacecraft control electronics comprises a profile generator configured to compute a desired orbit transfer profile such that perigee, apogee and inclination of the spacecraft are adjusted simultaneously in a mass-efficient manner. 12. The spacecraft as recited in claim 7 wherein the desired orbit transfer profile includes: placing the spacecraft in an Earth-pointed attitude when the spacecraft is at a predefined point in the trajectory;slewing the spacecraft from the Earth-pointed attitude to a desired orbit raising attitude; andsteering the spacecraft according to the desired orbit transfer profile while changing a spacecraft velocity. 13. The method as recited in claim 7, wherein the single positioning mechanism has two degrees of freedom. 14. A method comprising: dynamically computing an optimal steering profile for a spacecraft, based on position of the spacecraft on a trajectory, the spacecraft comprising at least one thruster disposed on a single positioning mechanism and an inertial reference sensor;dynamically computing the spacecraft's actual position;steering the spacecraft according to the computed optimal steering profile such that the at least one thruster imparts a change in velocity of the spacecraft along a desired direction;periodically shutting down the at least one thruster and reorienting the spacecraft;restarting the at least one thruster;autonomously repeating the above steps until the desired orbit is reached wherein three axis momentum management of the spacecraft is performed by: determining a respective momentum storage error (MSE) in each of three inertial spacecraft axes, said respective MSE comprising a difference, for each axis, between a momentum value actually stored on the spacecraft and a desired momentum value;reducing each respective MSE by producing, with at least one thruster disposed on a single positioning mechanism, a plurality of torques, by: orienting the thruster, with the single positioning mechanism, so as to produce a first torque that reduces the respective MSE of either or both of a first and a second of the three inertial spacecraft axes when the spacecraft is located at a first location on the trajectory, and,orienting the thruster, with the single positioning mechanism, so as to produce a second torque that reduces the respective MSE of at least a third of the three inertial spacecraft axes when the spacecraft is located at a second location on the trajectory; wherein,the single positioning mechanism is configured to orient the thruster so as to simultaneously (i) accelerate the spacecraft along a line of thrust and (ii) produce a torque around at least one of two axes substantially orthogonal to the nominal thrust vector; andas the spacecraft travels along the trajectory, a desired line of thrust undergoes a substantial rotation in inertial space. 15. The method as recited in claim 14, wherein the at least one thruster comprises a Hall effect thruster. 16. The method as recited in claim 14, where the inertial references sensor comprises a gyro that is reset to remove any drift when the spacecraft is in an Earth pointed orientation, using a calculated position of the Earth relative to the spacecraft, spacecraft orbital information and Earth sensor data. 17. The method as recited in claim 14, wherein the single positioning mechanism has two degrees of freedom.