Estudo dos erros sistemáticos inerentes a um sensor de estrelas de cabeça fixa, quando à localização relativa de estrelas / Study of systematic errors inherent to fixed-head star trackers with respect to the relative position of stars

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

Star trackers are attitude sensors used in spacecrafts capable of providing accurate attitude in arc-seconds range. The attitude information is provided when the star coordinates, measured by the sensor in its frame, are compared with known star directions obtained from a star catalog. Nevertheless, as in all measurement instruments, the measures are likely to be affected by systematic and random errors, which limit the sensor accuracy. In this work it is proposed a methodology of study, by computer simulation, of systematic errors inherent to fixed-head star trackers, with respect to the relative position of stars. These errors are influenced by the optical aberrations present in the image formed by the sensor objective lens; by the sample in the focal plane originated from the pixels and by the procedure used for stars centroid computation. Besides, correction techniques for these systematic errors are proposed in order to reduce them. The methodologies proposed here showed efficiency in the system where they were tested. The methodology presented to the study of stars relative position systematic errors, allows characterize the sensor pointing accuracy, whereas the corrective methodologies for this systematic errors showed efficiency in the tested system, reducing in 87,14% the systematic errors in the worst case evaluated. As far as the author is aware of, the methods of study and correction of systematic errors, in the way presented herein, represent an innovative contribution to the area. In this way, we hope to have contributed to the star tracker project currently being developed at Instituto Nacional de Pesquisas Espaciais(INPE).

ASSUNTO(S)

erros aleatórios space mechanics and control random errors optical measuring instruments sub-pixel accuracy mecÂnica espacial e controle image centroid precisão sub-pixel attitude angular resolution systematic errors aberrações resolução angular sensores ópticos de medida sensor de estrelas atitude erros de instrumento star trackers instriment errors erros sistemáticos centríode da imagem aberration

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