Voyager 1 was the first spacecraft to visit Jupiter and Saturn, it was launched in 1977, visited Jupiter in 1979 and Saturn in 1980, when its main mission was over. But 34 years on it is still doing science. Whilst Voyager 1's instruments may be outdated, and its radioactive power system is starting to run down, it is the furthest man made object from the earth, it is now 17.8 billion km from the sun over 120 times further than the earth is, and at least 3 times further than Pluto. So by being where no other spacecraft has been before it can still do new science.
At the moment it is passing through the edge of the Heliosphere where the sun's magnetic field is starting to be overwhelmed by the galactic magnetic field. This solar magnetic field deflects very high energy cosmic ray particles created when stars explode forming supernovae, so there should be fewer cosmic ray particles inside the Heliosphere than outside it.
In the three years up to January Voyager 1 saw a 25% increase in the galactic cosmic rays, which indicates that it is getting close to the boundary, but during may the cosmic rays increased by 9% in a month and 5% in a week, which in a 30 year mission is a very rapid change. It has also been seeing a drop in particles coming from the sun, though the final piece of data they need to be sure that it has left the sun, is if the direction of the magnetic field changes, but they need more data and time to analyse it to be sure.
The Voyager spacecraft are thought to have enough fuel and electrical power to last until 2025, so we may soon be finding what deep space is like.