Stray light performance of the long range reconnaissance imager (LORRI) on the New Horizons Mission

Abstract

The LOng-Range Reconnaissance Imager (LORRI) is a high resolution imaging instrument on the New Horizons spacecraft. New Horizons will collect data during a fly-by of Pluto and its satellites in 2015, and may continue on to collect data at another Kuiper Belt Object in an extended mission phase. New Horizons launched on January 19, 2006, the first mission of NASA's New Frontiers program. LORRI is a narrow field of view (0.29°), Ritchey-Chretien telescope with a 20.8 cm diameter primary mirror. The telescope has an effective focal length of 262 cm and has a three lens field flattener near the focal plane. The focal plane unit consists of a 1024 × 1024 pixel charge-coupled device detector operating in frame transfer mode. LORRI provides panchromatic imaging over a bandpass that extends approximately from 350 nm to 850 nm. The instrument operates in an extreme thermal environment, viewing space from within the warm spacecraft. For this reason, LORRI has a silicon carbide optical system with passive thermal control, designed to maintain focus without adjustment over a wide temperature range from -100 C to +50 C. LORRI has been successfully operated through initial commissioning, a fly-by of Jupiter, and two annual checkout periods. We describe the in-flight testing and measured performance of LORRI, and provide comparisons to pre-launch performance predictions. We also detail plans under consideration for changing LORRI's flight software to accommodate autonomous detection of targets within the instrument's field of view.