Active pixel sensor geometrical characteristic effects on star image subdivided locating accuracy for star tracker

Active pixel sensor (APS) star tracker becomes an investigated hotspot because of its technical advantages. And controid algorithm is a subpixel method proper to star position calculation because of its high accuracy and simplicity. When centroid algorithm is applied on APS star tracker, APS pixel geometrical characteristics might effect on star image position accuracy. Because the amplifier circuit and other function circuits inter pixel of APS take Lip some pixel area, the Fill Factor is less than 100%. Moreover, the active sensitive area has a certain geometrical shape, such as square, rectangle and L shape. The Fill Factor of pixel influences on star image subdivided locating accuracy when using centioid algorithm. In this paper, we have analyzed all pixel geometrical characteristics influence on the star position accuracy. From simulation experiments, we can conclude that Fill factor and pixel geometric shape influence on star position accuracy. The star locating error increased when Fill Factor decreased, and different geometrical shape of active sensitive area of pixel can make different influence on star location accuracy, the symmetrical sensitive area in x or y axis have symmetrical location error in the same axis.