text: It passed within 500 km of Rhea 's surface , downstream of Saturn 's magnetic field , and observed the resulting plasma wake as it had with other moons , such as Dione and Tethys .
simplified: It passed within 500 km of Rhea 's surface , downstream of Saturn 's magnetic field , and saw the resulting plasma wake as it had with other moons , such as Dione and Tethys .