Attitude Determination and Control System for the University of Missouri-Rolla Satellite Mission (UMR SAT)

This paper outlines the development and implementation of the Attitude Determination and Control System for the University of Missouri-Rolla Satellite mission (UMR SAT), one of eleven university entries into the Nanosat 4 competition administered by the Air Force Research Lab. The core objective of the mission is the development of autonomous control of formation flight. Due to budgetary constraints, this objective must be achieved using determination sensors and control hardware limited by mass, volume and cost. Attitude determination of the UMR SAT spacecraft is accomplished using only three-axis magnetometer measurements. Because the magnetic field measurement, provided by the magnetometer, only provides two-axis attitude information, the magnetic field derivative is used as well to resolve the third axis. The magnetic field derivative is obtained by filtering the magnetometer measurements with a standard extended Kalman filter. Both the magnetic field and derivative vectors are compared with a magnetic field model, provided to UMR SAT by the NASA Goddard Space Flight Center, to determine the real time attitude and angular velocity of the satellite. Attitude control is attained using low-cost magnetic coils and eight cold gas thrusters. The control software will use the coils and thrusters, appropriate to the current mission mode, to maintain the required satellite attitude