Abstract: Spacecraft payload orientation steering is provided for an orbiting spacecraft in motion along an orbit track around a celestial body, the orbit track having a nominal inclination with respect to an equatorial orbit, a substantial eccentricity, and a drift angle with respect to the nominal inclination. Coordinates of an optimal payload target location as a function of a spacecraft position along the orbit track are determined, the target location being on the surface of the celestial body and having a substantial motion with respect to the surface and with respect to a spacecraft nadir. A payload of the spacecraft is substantially aligned with the determined coordinates by steering the satellite body to correct for at least one of the inclination drift angle, and the eccentricity, thereby adjusting the spacecraft orientation as a function of the spacecraft position along the orbit track.

Abstract: Spacecraft payload orientation steering is provided for an orbiting spacecraft in motion along an orbit track around a celestial body, the orbit track having a nominal inclination with respect to an equatorial orbit, a substantial eccentricity, and a drift angle with respect to the nominal inclination. Coordinates of an optimal payload target location as a function of a spacecraft position along the orbit track are determined, the target location being on the surface of the celestial body and having a substantial motion with respect to the surface and with respect to a spacecraft nadir. A payload of the spacecraft is substantially aligned with the determined coordinates by steering the satellite body to correct for at least one of the inclination drift angle, and the eccentricity, thereby adjusting the spacecraft orientation as a function of the spacecraft position along the orbit track.

Abstract: A method for use in a spacecraft for controlling yaw angle deviations from a desired yaw angle profile. The method includes the steps of: (a) operating a profile generator to output roll angle, pitch angle, yaw momentum, and yaw angle profiles, the profiles being calculated to meet spacecraft pointing requirements while operating in an inclined orbit; (b) inputting to an observer raw roll-axis sensor measurements, commanded and measured yaw-axis wheel momentum storage, measured pitch-axis wheel momentum storage, and external roll-axis and yaw-axis torques, the observer generating a yaw angle estimate and a yaw momentum estimate; (c) subtracting the yaw angle profile from the yaw angle estimate to obtain a difference value; and (d) using the difference value and the yaw momentum estimate to control roll-axis thruster firings to limit spacecraft yaw angle deviations from the yaw angle profile.