DAYSIDE-ONLY ROLL STEERING

A method of roll steering of a spacecraft to align an aspect of the spacecraft, such as the surface of solar arrays carried by the spacecraft, to the sun, is described. The roll steering occurs only when the sun is at an angle (β) relative to the orbital plane of the spacecraft and when the spacecraft is not eclipsed by a body it is orbiting. This dayside-only roll steering of the spacecraft increases the power efficiency of the spacecraft. A spacecraft may include a controller which causes an attitude control subsystem to steer the spacecraft about a roll axis to position the surface of the solar array such that an axis normal to the surface of the solar array is aligned with the direction to a sun when the sun is visible to the spacecraft, and maintain a fixed orientation of the spacecraft about the roll axis when the sun is not visible to the spacecraft.