1. which were developed and successfully ground-tested in December 199916. The boomdesign has been
2. assumption in designing the power subsystem is the 8W/kg specific power figure (2ndgeneration RTG) and a degradation rate of 1 W/year. A typical RTG, e.g. Cassini uses 18 GPHS modules with an output of ~4500W thermal, or 290W electrical at BOL. Hence around 4200W of thermal power must be radiated, hence the large fins and the heat shield between the RTG and the spacecraft. The GPHS RTG has a mass of 54kg, and is commonly mounted on a spacecraft exterior space where it can radiate to space, the New Horizons Pluto mission has this mounted horizontally with the spacecraft in the launch vehicle shroud indicating ease of structural mounting. The Multi-Mission RTG (MMRTG) under development for Prometheus is based on the GPHS module, with a desired power output of 100W estimated from a wide ranging mission analysis30,31. The goal of the MMRTG program is to provide sufficient power for many missions while reducing the carried Plutonium. For a mass of 34kg, a BOL power of 120W is projected (3.5W/kg), decreasing to 110W (3.2W/kg) at EOL, after 10-14 years30, 31. This employs the same conversion components as the current RTGs but is shorter and fatter (estimated 58 cm long x 84 cm wide). Larger individual units are not planned, but missions requiring>120Wwill require usingmore than one MMRTG. B. RF System
3. phase (60 rpm), Meteosat/GEO platforms during their transfer phase (> 60 rpm), Cluster (10-15
4. than to otherspacecraft32-35.