---

Benjamin Abeles and George Cody Exxon Research and Engineering, Annandale T he Voyager space probes have been described as "an epic journey to the four giant gas planets of our solar system." The invention that made the Voyager mission possible, the silicon-germanium thermoelectric power generator, was developed in the 1960s by Benjamin Abeles and George Cody at the David Sarnoff Research Center in Princeton. While studying the high temperature properties of semiconductors the pair discovered unexpectedly low thermal conductivity in silicon-germanium alloys. By doping the alloys with impurities, they further lowered the thermal conductivity and optimized the electrical properties needed to efficiently convert heat to electricity at high temperatures. This discovery led to the development of a reliable and longlived source of energy, perfect for deep space probes which cannot use solar panels to collect energy. In 1980, the Franklin Institute presented the prestigious Stuart Ballentine Medal for advancing communications using thermomagnetic radiation to the researchers.