NASA's Cassini spacecraft, launched in 1997, is on a journey to Saturn to study the planet's atmosphere, magnetic field, rings, and several moons. It flew by Jupiter in December 2000 and carries the Huygens Probe to be ejected towards Saturn's moon Titan in 2004.

Launched in 1989, the NASA spacecraft Galileo has been orbiting Jupiter since late 1995. It shut down all systems after being exposed to radiation from a close flyby of the moon Amalthea on November 6, 2002.

A proposed NASA mission designed to fly by and make studies of the planet Pluto, its moon Charon, and one or more of the large bodies in the Kuiper belt beyond Pluto's orbit. Work on this mission has been delayed for budgetary reasons; George W. Bush's 2002 spending blueprint for NASA, released February 28, 2001, provided no funding for the Pluto-Kuiper Express. However on February 20, 2003, a bill was signed by President Bush securing funding for a 2006 launch.

Launched in to 1960s and 1970s, NASA's Pioneer spacecraft made the first detailed observations of Saturn and Jupiter.

The twin Voyager 1 and 2 spacecraft were launched in 1977 to explore the outer solar system. More than 25 years later they are approaching the solar system boundary region -- the heliopause -- where the Sun's dominance of the environment ends and interstellar space begins. The primary mission was the exploration of Jupiter and Saturn. After making a string of discoveries there -- such as active volcanoes on Jupiter's moon Io and intricacies of Saturn's rings -- the mission was extended. Voyager 2 went on to explore Uranus and Neptune, and is still the only spacecraft to have visited those outer planets. The adventurers' current mission, the Voyager Interstellar Mission (VIM), will explore the outermost edge of the Sun's domain.