Application of Magnetic Sensors to Nano- and Micro-Satellite Attitude Control Systems

These days, nano (1 kg – 10 kg ) and micro (10 kg – 100 kg) – satellites, which are smaller than conventional large satellite, provide space access to broader range of satellite developers and attract interests as an application of the space developments because of shorter development period at smaller cost. Several new nanoand micro-satellite missions are proposed with sophisticated objectives such as remote sensing and observation of astronomical objects. In these advanced missions, some nanoand micro-satellites must meet strict attitude requirements for obtaining scientific data or high resolution Earth images. Example of these small satellites are nano remote sensing satellite PRISM, which should be stabilized to 0.7 deg/s (Inamori et al, 2011(a)), and nano astronomy satellite ”Nano-JASMINE”, which should be stabilized to 1 arcsec (Inamori et al, 2011(b)). Most of these small satellites have the strict constraint of power consumption, space, and weight. Therefore, magnetometers which are lightweight, reliable, and low power consumption sensors are used in the most of these small satellite missions as a sensor for an attitude determination system. In addition, most of these satellites use magnetometers for the attitude control systems with magnetic actuators to calculate required output torque. Furthermore, in some nanoand micro-satellite missions, a magnetic moment is estimated using magnetometers to compensate the magnetic moment and magnetic disturbance. In these small satellite missions, magnetometers play a more important role than conventional large satellites to achieve the attitude control. Although the magnetometers are useful for nanoand micro-satellite attitude control systems, these sensors which are not calibrated are not suitable for an accurate attitude control because of the measurement noises which are caused from magnetized objects and current loops in a satellite. For a precise attitude estimation, many satellites use heavier and higher power consumption sensor such as star truckers and gyro sensors, which are difficult to be assembled to some small satellites. To achieve the accurate attitude control in the small satellite missions, the magnetometers should be calibrated precisely for the accurate attitude control system. This chapter will present what is the requirement for magnetometers in the nanoand micro-satellite missions, how these magnetometers are used in these small satellite missions.