Where are the Voyager probes now, and are we still receiving information from them?

Question posed by Jennie.

The Voyager spacecraft were launched in 1977 with the mission of visiting and collecting data about Jupiter (Voyager 1) and Saturn (Voyager 1 & 2), and other objects and features around them such as moons and ring systems. With the probes designed to last for five years, the initial mission was completed in 1981, with Voyager 1 already on a trajectory that would eventually send it out of the solar system. Voyager 2, however, had been sent straight to Saturn (missing Jupiter) on a trajectory that would allow it to fly on to Uranus (arriving in 1986) and Neptune (in 1989) and so complete the Voyager Neptune Interstellar Mission.

Voyager 2's encounter with Neptune set it, like its twin, on a trajectory out of the solar system, never to return. The mission was extended again, and named the Voyager Interstellar Mission, and both spacecraft continue to collect data about their environment and send it back to Earth.

So where are they now?


Voyager 1
Having far outlived its designed life span, Voyager 1 is currently the furthest man made object away from the Earth, and is travelling out of the solar system at a speed greater than any other probe currently in space, including Voyager 2. This means that it will retain this record for the foreseeable future.

As of 2009, Voyager 1 is more than 110 Astronomical Units (AU) away from the sun - that's 2-3 times further away than Pluto and further out than any known solar system body excluding long-period comets - and travelling at a speed of about 61,600 kilometres per hour, which means that it is moving about 3.6 AU away from us each year. Signals from Voyager 1, travelling at light speed, take around 15 hours to reach Earth - to put this in perspective, light from the Sun takes about 8 minutes to get to us.

The spacecraft has passed the solar system's termination shock* and entered the heliosheath*. Part of Voyager 1's ongoing mission is to study both of these solar system features, with the goal of reaching the heliopause**.


Voyager 2
In 2009, Voyager 2 is around 90 AU from the Sun (more than twice as far away from us as Pluto), and leaving the solar system at a rate of around 3.3 AU per year in a different direction to Voyager 1. Voyager 2 has also crossed the termination shock boundary, but did so around 1,600,000,000 kilometres closer to the Sun than its twin did, providing information that suggests the solar system is not a perfect sphere, but squashed. Voyager 2 is also on a continuing mission to study the heliosheath and, eventually, the heliopause.


To infinity and beyond?
Even though both spacecraft have far outlived their design specifications, the Voyager probes' power sources*** will eventually dwindle to a point at which they can no longer power their scientific instruments. NASA have developed a schedule that outlines when each of the probes' capabilities will be shut down due to limitations in electrical power, and expect both spacecraft to be transmitting data back to Earth until at least 2025, almost 50 years after their launch.




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*  These terms are too complicated to explain fully here, and would be better off in a post of their own, but in very simple terms:

• The termination shock is a sort of boundary to the solar system where the solar wind particles emitted by the Sun are slowed down by their interaction with the local interstellar medium.
• The heliosheath is a region outside the termination shock where the slowed down solar wind particles interact further with the interstellar medium and become turbulent.
• The interstellar medium is the matter that exists mainly in the form of gas and dust in the spaces between (inter) the stars (stellar).

** Again, an explanation of the heliopause would require a post of its own (or, rather, would appear in a general post about the heliosphere), but in simple terms, the heliopause is the boundary of the solar system. Once the Voyagers cross this, they have very definitely grown up and left home.

*** Both probes are powered by three Radioisotope Thermoelectric Generators (RTGs), if you're interested.