Design and Simulation of a Star Tracker for the Aramis Small Satellite

Star Trackers are devices that provide higher accuracy than other attitude sensors
with the added benets of 3-axis attitude determination. Nevertheless, Star Trackers
are frequently heavy, complex and costly systems that can not be adopted by small
satellites such as the Aramis from Politecnico di Torino, which needs high-accuracy
attitude determination to cover the requirements of certain types of payload.
In this thesis, the state of the art in attitude sensing is described, specially that
of Star Trackers. Then, a preliminary design of a low-mass, low-cost, low-power and
coarse accuracy Star Tracker is proposed to satisfy the requirements of the Aramis
spacecraft.
Dierent available algorithms for identifying the presence of single stars on the
imager plane are analyzed, as well as those for pattern recognition necessary to
ultimately measure the spacecraft attitude. One set of such image processing and
pattern recognition algorithms are chosen for use on board Aramis. Subsequently,
they are tested with the experimental use of the 3D open source planetarium Celestia,
while a parallel test of the image processing algorithms is performed on real
star eld imagery to conrm their capabilities with real-world data.
A scheme is proposed to reduce the amount of false results thanks to the use
of attitude approximations coming from other sensors, through the homogeneous
segmentation of the celestial sphere.
Commonly used methods to produce the desired quaternion output are described,
and nally, an assessment of the performance of the tested algorithms is made.