text: The Galileo spacecraft launched on October 18, 1989, the Ulysses on October 6, 1990, the Cassini on October 15, 1997, and the New Horizons on January 19, 2006. All of these spacecraft contain the general purpose heat source (GPHS) RTG commissioned by the U.S. Department of Energy.  The GPHS-RTG employs identical heat-to-electrical conversion technology used in the MHW-RTGs from the Voyager missions, using SiGe thermocouples/unicouples and the Pu-238–fueled GPHS. New Horizons made its historic flyby  past Pluto and its moons on July 14, 2015 ([http://pluto.jhuapl.edu/ see JHU Applied Physics website]). The spacecrafts next destination will be a small Kuiper Belt object (KBO) known as 486958 Arrokoth that orbits nearly a billion miles beyond Pluto. Based on performance, data and modeling for the SiGe alloy RTGs, the GPHS-RTGs on Ulysses, Cassini and New Horizons' are expected to meet or exceed the remaining power performance requirements for their deep-space missions.