Abstract:
The development of an Attitude Determination System (ADS) based on a Star Tracker is
described. The ability to achieve the performance required to enable optical alignment from
Low Earth Orbit (LEO) to ground station is investigated. Commercially available (COTS)
hardware, and open-source software, are selected to design and simulate the Star Tracker.
The unit is intended for implementation in a U-class nanosatellite, also defined as CubeSat.
A review of ADSs based on Star Trackers is presented, including heritage satellite missions
implementing similar hardware. The importance of the Star Tracker as a self-sufficient
attitude sensor is highlighted. Concepts and techniques aimed to improve the performance
of pointing accuracy and sampling frequency are analysed and implemented. A program
simulating the celestial sphere is developed to produce synthetic calibrated images of the
starfields surrounding Earth. The algorithms implemented in the Star Tracker are tested using
synthetic images, and the results are presented. The Star Tracker produces attitude solutions at
a sampling frequency of 1:83 Hz, with a pointing accuracy of 11:051° when pointing between
-90° and 90° Declination, and a pointing accuracy of 0:244° when pointing between -45° and
45° Declination. The Star Tracker based ADS system demands further development to achieve
the intended performance, but a promising approach for the reduction of mass, volume and cost
in the development of an ADCS for CubeSats is presented.