Patent ID: 7681841

Claim:
A method for power acquisition, the method comprising: a) in a spacecraft having a solar wing and a sun sensing apparatus consisting of a single-axis slit sun sensor having a boresight, executing a wing sun search phase in which the solar wing continuously searches for the sun to face toward the sun for strong solar power reception and a solar wing current is monitored against a low current threshold; b) executing a body search phase in which the spacecraft rotates about a search axis that is substantially parallel to or in the same plane as the field of view plane of the single-axis slit sun sensor and perpendicular to the boresight of the single-axis slit sun sensor; c) monitoring the single-axis slit sun sensor for a time of arrival (TOA) signal; d) if the TOA signal occurs, rotating the spacecraft along the search axis to an orientation where the TOA signal occurred and placing the spacecraft in stable rotation about an axis coincident with or substantially parallel to a solar wing longitudinal axis; and e) if the TOA signal does not occur, executing a keyhole slew phase in which rotation of the spacecraft about the search axis is halted and the spacecraft is rotated about a keyhole axis coincident with or substantially parallel to the solar wing longitudinal axis through a predetermined angle based on the field of view of the single-axis slit sun sensor and a potential control error to move the sun away from a keyhole, and repeating steps b), c) and d); wherein the steps are performed in the order a)-b)-c)-d) or a)-b)-c)-e).