Method and system for spacecraft power acquisition using single-axis slit sun sensor

A method for power acquisition, the method comprising:

• a) in a spacecraft having a solar wing in a stowed state and a sun sensing apparatus, the sun sensing apparatus consisting of a single-axis slit sun sensor having a boresight, wherein an x-axis extends through or is parallel with the boresight, a y-axis extends through or is parallel with the spacecraft solar wing when it is in a deployed state, and a z-axis is perpendicular to the x-y plane, executing a yaw search phase in which the spacecraft rotates about the z-axis;
• b) monitoring the single-axis slit sun sensor for a time of arrival (TOA) signal at which the sun lies in the plane defined by the single-axis slit sun sensor's field of view;
• c) if the TOA signal occurs, resetting the spacecraft's attitude estimate and attitude command to identity at the orientation where the TOA signal occurred, rotating the spacecraft an additional ninety degrees about the z-axis from the orientation where the TOA signal occurred to orient the solar wing toward the sun, halting rotation about the z-axis and rotating the spacecraft about the x-axis;
• and
• d) if the TOA signal does not occur, executing a keyhole slew phase in which rotation of the spacecraft about the z-axis is halted and the spacecraft rotates about the y-axis through a predetermined angle based on the single-axis slit sun sensor field of view and a potential control error to move the sun away from a keyhole, and repeating steps a), b) and c);
• wherein the steps are performed in the order a)-b)-c) or a)-b)-d).

A spacecraft having a body reference frame with three mutually perpendicular axes, said spacecraft comprising:

• a solar wing having a plurality of solar panels;
• a sun sensing apparatus consisting of a single-axis slit sun sensor for providing a time of arrival (TOA) signal, the sun sensor having a boresight;
• and
• a set of gyros used to propagate attitude estimate;
• wherein the three mutually perpendicular axes comprise a roll axis extending through or parallel with the boresight, a pitch axis extending through or parallel with the spacecraft solar wing when it is in a deployed state, and a yaw axis perpendicular to a plane defined by the roll axis and the pitch axis;
• wherein the spacecraft is configured to perform a yaw search phase in which the spacecraft rotates about the yaw axis and the single-axis slit sun sensor is monitored for a TOA signal at which the sun lies in the plane defined by the single-axis slit sun sensor's field of view;
• wherein if the sun is detected crossing the single-axis slit sun sensor's field of view the spacecraft's attitude estimate and attitude command are reset to identity and the spacecraft rotates an additional ninety degrees about the yaw axis to orient the solar wing toward the sun, and the spacecraft rotates about the roll axis;
• and
• if the sun is not detected crossing the single-axis slit sun sensor's field of view, the spacecraft executes a keyhole slew phase in which rotation of the spacecraft about the yaw axis is halted and the spacecraft is rotated about the pitch axis through a predetermined angle based on the single-axis slit sun sensor field of view and a potential control error to move the sun away from a keyhole.