<h2>AAS 99-182</h2>
<h2>Star Pattern Recognition and Mirror Assembly Misalignment for DIGISTAR II and III                                                                </h2>
<h4>Star Sensors                                                                                                                                                                        </h4>
D. Mortari, M. Angelucci                                                                                                                                                  
<h2> Abstract </h2>
Two crucial aspects for the data processing of the recently proposed DIGISTAR II and DIGISTAR III multiple-FOV star trackers, which use one/two mirrors deflecting the sensor FOV to two/three orthogonal directions, respectively, are analyzed. These aspects concern the star-ID process and the mirror misalignment estimation. It is shown how to adapt the K-vector technique, which does not require any searching phase, to these sensors and, in order to keep the obtained gain in the attitude accuracy, two methods to compute the mirror misalignment are provided. The first method evaluates the misalignment by a least-square approach and it can be used for small misalignment, that is, such that the star-id process can still be performed. The second method can be used for any value of the misalignment but it implies that the star identification process can be performed for each sub-FOV. Results and tests of both methods are shown.