Star tracker scan mode capability for the New Horizons mission

The New Horizons mission to Pluto and the Kuiper Belt is scheduled for launch in early 2006. The overall mission design requires a star tracker that operates autonomously both in a standard “staring” mode and in a star scanning mode. With the support of APL and the New Horizons Program, Galileo Avionica S.p.A. has redesigned the software for their A-STR star tracker to use time-delayed integration techniques (TDI) to provide autonomous spacecraft attitude estimates at 10 Hz and at spacecraft spin rates up to 10 RPM. This paper will present the design considerations and operating modes for the modified A-STR tracker, as well as expected accuracy performance.