Abstract: A zero-momentum spacecraft's attitude is controlled by determining the torque required about a control axis to maintain the desired attitude, and, during each of recurrent control cycles, enabling a magnetic torquer if the torque demand exceeds a threshold. During each of the control cycles, thruster(s) are enabled to make up the difference between the torque demand and the estimated torque produced by the magnetic torquer. In determining the torque demand, the attitude rate signal is low-pass filtered to reduce noise, and the control loop bandwidth is maintained by totalling the estimated torque applied by the magnetic torquer and thrusters, integrating and high-pass filtering the estimated torque signals, and adding the filtered estimated torque with the filtered attitude rate signals to generate low-noise attitude rate signals. A three-axis system is described.

Abstract: An improved system and method for ejecting and stabilizing a satellite/perigee stage assembly from a shuttle or orbiter type craft in space where the satellite includes gyros aligned parallel to three orthogonal axes, a computer, and spin and attitude control thrusters is described. The method comprises the steps of orienting the shuttle such that the perigee motor is pointing in the desired firing attitude, initializing said gyros and initializing the attitude determination algorithm in the spacecraft's computer, ejecting the spacecraft/perigee stage assembly without spin, after ejecting, slowly spinning the assembly about a desired spin axis, damping the assembly's nutation and precessing the assembly to the initial attitude while slowly spinning, and when at the initial attitude, spinning up the assembly for perigee motor firing.

Abstract: A closed-loop magnetic roll/yaw control system for high inclination satellites where the predominant component of the geomagnetic field lies in the orbit plane of the satellite. The system includes a torquing means that forms a magnetic dipole moment parallel to the pitch axis. The torquing means is energized to minimize roll or yaw error only in two spaced portions 1 and 3 of its orbit. Each of the portions lie between the extension of the earth's magnetic equatorial plane and a second plane normal to the orbit and passing through the magnetic poles of the earth. Portions 1 and 3 are those parts of the orbit in which the satellite is traveling toward the second plane. The torquing means is de-energized after the satellite crosses the second plane and is in either of the remaining spaced portions 2 and 4 of its orbit.