Digistar II micro-star tracker: Autonomous on-orbit calibration and attitude estimation
Additional Document Info
A recursive on-orbit calibration approach for the recently proposed DIGISTAR II split field-of-view (FOV) star tracker, which use one mirror deflecting the sensor FOV to two orthogonal directions, is presented. This calibration study includes the corrections to effective focal lengths, focal plane offsets, interlock angles due to mirror misalignment, lens distortion and electronic aging nonlinearities. The process can be performed by retaining the residuals between the measured star image centroid locations and the projected estimated image coordinates, for several hundred frames. Gaussian Least Square Differential Correction (GLSDC) is used to update the correction terms recursively. Final best attitude estimation approach based upon the recursive calibration is then summarized. Numerical simulation is also performed to generate simulated image data and to validate this approach. In addition, the novel features of DIGISTAR I & II are described with hardware specifications and software algorithms for star identification and attitude determination.