The Variable Radioisotope Heater Unit for the Cassini Spacecraft

This paper describes the Variable Radioisotope Heater Unit; its development, performance, and effectiveness at controlling the temperatures for the Cassini spacecraft thruster clusters.

To explore the Saturn system, the Cassini spacecraft relies on the electrical power from three Radioisotope Thermoelectric Generators, but the large power demand for science and engineering functions severely limits the electrical power available for temperature control purposes. The Variable Radioisotope Heater Unit combines the heating- and temperature-control functions into one nonelectrical self-controlled unit, thereby freeing up electrical heater power for other uses on the spacecraft.