The NASA space probes Voyagers 1 and 2 are currently in the Heliosheath, which is the outer part of the Heliosphere. This is where the solar system ends and outer space begins, these two probes will become the first man made objects to leave the solar system and venture into outer space some thirty three years after being launched.
According to the NASA Voyager website this is what the primary mission for the Voyager probes are;
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. And beyond.
Source [Geeks Are Sexy]