Magnetostatic cleanliness of the radioisotope thermoelectric generators (RTGs) of Cassini

The Cassini spacecraft, launched in October 1997 to reach Saturn in 2004, carries two magnetometer experiments on a 10-meter boom, one at the mid-section of the boom and the other at the end of the boom. In order to gather valid scientific magnetic field data and avoid electromagnetic interference, the spacecraft had to comply with stringent magnetostatic cleanliness requirements. Amidst the strongest magnetic field perturbations were three radioisotope thermoelectric generators (RTGs), which provide power to the spacecraft's engineering subsystems and science instruments. The RTGs have been compensated efficiently. This paper describes the field-mapping technique, the numerical modeling and the compensation approach used for the RTGs with the goal of minimizing its magnetic field interference with Cassini's DC magnetic field science instruments. A short synthesis of the total spacecraft cleanliness level is also given.