an extended mission to at least one Kuiper Belt Object in subsequent years. The concept of operations requires a star tracker that operates autonomously both in a standard 3-axis "staring" mode during operations involving instrument observations and in a spin stabilized mode during cruise operations with nominal rotational rates up to 5 RPM. With the support of the Johns Hopkins University Applied Physics Laboratory, Galileo Avionica redesigned their autonomous star trackers (ASTR) to use time-delayed integration techniques to provide autonomous spacecraft attitude estimates at 10 Hz at spin rates up to 10 RPM. This paper will present the performance of the upgraded ASTR in both inertial stare and spin stabilized modes for the first six months of the mission. In addition, effects of the vehicle motion on performance, effects of stray light and direct Sun blinding on tracking and performance, and unanticipated "features" or characteristics of the ASTRs will be discussed. Star Tracker 1 ASTR 1 S/N 0019 RT Address 9 Star Tracker 2 ASTR 2 S/N 0020 RT Address 25 ASTR 1 X ASTR 2 X ASTR 2 Z ASTR 1 Z ASTR 2 Y ASTR 1 Y + Y LORRI RALPH
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