ESA GNC Conference Papers Repository
Precision ADCS of cubesats by on-orbit determination of the dynamic magnetic moment
CubeSats and Nano-Satellites are being increasingly specified for demanding Earth Observation and Astronomical applications where precise pointing and stability, and the ability to move quickly from one attitude state to another, are critical requirements. Such precision is difficult in the case of CubeSats and NanoSats as, firstly, their small moments of inertia mean that even small disturbance torques, such as those due to a residual magnetic moment, have a significant effect. Secondly, there are attitude determination and control system (ADCS) hardware limitations in terms of power, weight and size, which make the task of precision attitude control more challenging. Recently, a PhD research programme has been undertaken at the Surrey Space Centre (SSC), to study the source of the residual magnetic moment in CubeSats, and to characterise the effect of the resulting magnetic disturbance on the attitude of the spacecraft. It has been found that, although the disturbances may be minimised by good engineering practice, in terms of minimising the use of permeable materials, and minimising current-loop areas by good system layout, these disturbances can still be an issue when stabilities better than 1 degree are required. The dynamic nature of the disturbances requires an active mitigation strategy. To this end, we propose a new technique, using a network of magnetometers to characterize and compensate the residual magnetic moment - in flight and in real time. Magnetometer readings data have been taken from the https://ukamsat.files.wordpress.com/2016/09/alsat-1n_description_v1.pdf CubeSat and used in simulation. Hardware implementation is being devolved to fit into the engineering model of Alsta-1N and https://directory.eoportal.org/web/eoportal/satellite-missions/a/aarest. This paper reports on our findings to date.