Spacecraft payload orientation steering

摘要

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.

主权项

1. A method comprising:
determining, as a function of a position of a spacecraft along an orbit track around a celestial body, time varying coordinates of a non-fixed target location, the non-fixed target location having a substantial motion with respect to a fixed fit-target on a surface of the celestial body and with respect to a spacecraft nadir, said orbit track having one or both of (i) an eccentricity of at least 0.2, and (ii) an inclination with respect to an equatorial orbit of at least 50 degrees; and substantially aligning an antenna reflector of the spacecraft with the determined time varying coordinates by actively steering the spacecraft orientation as a function of the position of the spacecraft along the orbit track such that a boresight of the antenna reflector points to the determined time varying coordinates, wherein actively steering the spacecraft orientation includes:
determining an actual orbit position of the spacecraft;computing, for the determined actual orbit position, a desired inertial attitude of the spacecraft in terms of fitted expressions related to payload optimized roll angle, ΦFIT, pitch angle, θFIT, and yaw angle, ΨFIT, whereinone or more of ΦFIT, θFIT, and ΨFIT are expressed as a sum of a first function that computes a steering angle to the fixed fit-target and a respective second or third function modeling a fitted profile away from the fit-target.