On October of 1997, a two-story-tall robotic spacecraft will begin a journey of many years to reach and explore the exciting realm of Saturn, the most distant planet that can easily be seen by the unaided human eye. In addition to Saturn's interesting atmosphere and interior, its vast system contains the most spectacular of the four planetary ring systems, numerous icy satellites with a variety of unique surface features. A huge magnetosphere teeming with particles that interact with the rings and moons, and the intriguing moon Titan, which is slightly larger than the planet Mercury, and whose hazy atmosphere is denser than that of Earth, make Saturn a fascinating planet to study.
The Cassini mission is an international venture involving NASA, the European Space Agency (ESA), the Italian Space Agency (ASI), and several separate European academic and industrial partners. The mission is managed for NASA by JPL. The spacecraft will carry a sophisticated complement of scientific sensors to support 27 different investigations to probe the mysteries of the Saturn system. The large spacecraft will consist of an orbiter and ESA's Huygens Titan probe. The orbiter mass at launch will be nearly 5300 kg, over half of which is propellant for trajectory control. The mass of the Titan probe (2.7 m diameter) is roughly 350 kg.
The mission is named in honor of the seventeenth-century, French-Italian astronomer Jean Dominique Cassini, who discovered the prominent gap in Saturn's main rings, as well as the icy moons Iapetus, Rhea, Dione, and Tethys. The ESA Titan probe is named in honor of the exceptional Dutch scientist Christiaan Huygens, who discovered Titan in 1655, followed in 1659 by his announcement that the strange Saturn "moons" seen by Galileo in 1610 were actually a ring system surrounding the planet. Huygens was also famous for his invention of the pendulum clock, the first accurate timekeeping device.