초록 ▼

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

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.

대표청구항 ▼

[ What is claimed is:] [1.] A method of acquiring the Earth by a three-axis stabilized spacecraft, the spacecraft having an Earth sensor with a boresight direction and a Sun sensor with a boresight direction, wherein a first vector from the spacecraft to the Sun defines a Sun vector, a second vector

[ What is claimed is:] [1.] A method of acquiring the Earth by a three-axis stabilized spacecraft, the spacecraft having an Earth sensor with a boresight direction and a Sun sensor with a boresight direction, wherein a first vector from the spacecraft to the Sun defines a Sun vector, a second vector from the spacecraft to the Earth defines a nadir vector, and wherein the angle between the Sun vector and the nadir vector defines a Sun-Earth separation angle, the Sun-Earth separation angle changing over time due to the relative movements of the Earth, the Sun and the spacecraft, the method comprising:obtaining an Earth cone described by rotating the nadir vector about the Sun vector;determining a slewing axis by taking the cross product of the Earth sensor boresight with the Sun sensor boresight;determining which edge of the Earth cone will be used to stop the slew based on the desired final attitude of the spacecraft;slewing the spacecraft about the slewing axis until the Earth sensor boresight touches the determined 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;locking onto the Earth so as to hold the Earth sensor boresight coincident with the nadir vector; androtating the spacecraft about the nadir vector so as to bring the spacecraft into a desired final orientation.