Hi Doug,

I'm going to suggest that the two STEREO spacecraft win this contest,if you mean traveled the farthest from Earth. Both are still in orbit about the Sun at about the same distance from the Sun as Earth is...1 Astronomical Unit..but both are separated from Earth by about 120 degrees. And this angle is increasing. When they get directly behind the Sun --directly across Earth's orbit from us -- they will be 2 AU from Earth!

The spacecraft that go to the outer solar system...Jupiter and beyond...all use a form of nuclear energy.

Paulett

Hi Doug,

The Mars rovers would not beat out STEREO right now as being the furthest spacecraft to use solar panels because Mars is only about 1.6 AU away! However, the Juno mission to Jupiter launched in 2011 will soon become the spacecraft to have traveled the furthest away from Earth that uses power from solar panels. Right now Juno is located just outside the orbit of Mars, but it is heading back into the inner solar system for an Earth flyby gravity assist maneuver to help it arrive at Jupiter in 2016. Juno is the first mission to the outer planets to use solar panels, thanks to recent advances in technology. All previous missions to the outer planets and the New Horizons mission (launched 2005) currently on its way to Pluto had to use radioactive materials to generate electricity.

Kris

HI Doug

I've just learned that while STEREO might hold the record now, NASA's Juno mssion to Jupiter will win the prize when it gets out toward Jupiter. It is solar powered--VERY large solar arrays. Right now, Juno is still picking up speed in the inner solar system..in fact it is now heading towards Earth! Spacecraft use Earth flybys to pick up more speed.

Paulett

A co-worker here at the University of Iowa who worked on one of the instruments on Juno just showed me this nifty NASA web site that will show you where various spacecraft are located and let you determine distances between spacecraft and different planets right now:

http://eyes.nasa.gov

To get the distance measuring tool, click on the symbol on the lower left hand side under "Destination" that looks like a hammer & wrench, and it should give you instructions on what to do.

Kris

Doug,

Well, we were wrong. A colleague points out that NASA's DAWN spacecraft is now out in the asteroid belt. It uses solar power to run an ion engine. Last year it reached the asteroid Vesta, 117 million miles from Earth.The DAWN spacecraft has been en route for about four years, traveling 1.7 billion miles across the sky, and is spending one year orbiting Vesta before heading for the dwarf moon Ceres (ETA February 2015).

Paulett