Satellite gravity gradient compensation using on-orbit solar array reorientation

A method for operating a three axis stabilized orbiting spacecraft of a type that includes a plurality of solar array panels, the orbiting spacecraft having principal moments of inertia Ixx, Iyy and Izz along X, Y and Z axes, respectively, of an orbital coordinate frame, comprising the steps of:

• changing a mass distribution of the spacecraft from a first mass distribution by varying an angular position of at least two of the solar array panels away from a sun-pointing configuration for setting one of a pair of Ixx and Iyy, Iyy and Izz, and Ixx and Izz approximately equal to one another, thereby minimizing a gravity gradient torque about a third axis that is not an axis associated with the pair of principal moments of inertia that are approximately equalized;
• performing a desired activity while the gravity gradient torque about the third axis is minimized;
• and
• resetting the mass distribution back to the first mass distribution at a completion of the desired activity by varying the angular position of the at least two solar array panels towards the sun-pointing configuration.

A method for stabilizing an orbiting spacecraft, comprising the steps of:

• altering a mass distribution of the spacecraft from a first mass distribution for setting a first principal moment of inertia of the spacecraft along a first axis to be greater than a second principal moment of inertia of the spacecraft along a second axis, thereby reversing a sign of a gravity gradient torque upon the spacecraft and resisting a rotation of the spacecraft about a third axis;
• performing a desired activity while the sign of the gravity gradient torque is reversed;
• and
• resetting the mass distribution back to the first mass distribution at a completion of the desired activity;
• wherein
• the spacecraft includes a plurality of solar array panels, wherein the step of altering is accomplished by varying a position of at least two of the solar array panels away from a sun-pointing configuration, and wherein the step of resetting is accomplished by varying the position of the at least two solar array panels back to the sun-pointing configuration.