The "asteroid belt" is unimaginably sparsely populated. Nothing like you see in Star Wars with spaceships dodging and weaving around dense fields of rocks. Asteroids are separated by a million kilometers. The chance of hitting anything at all on a random trajectory is extremely low, on the order of one in a million.

http://physics.stackexchange.com/questions/26712/what-is-the...

http://wiki.answers.com/Q/What_is_the_average_distance_betwe...

Star Wars the Empire Strikes Back did some horrible things to a lot of people's conceptions about asteroid belts.

The asteroid belt is so unbelievably sparse, you would never even know you are flying through it. Absolutely no concern was given to the prospect of a collision.

To give you some perspective, as a test they flew one of the pioneer spacecraft through the rings of saturn, even the rings of saturn are so sparse that the spacecraft flew through completely untouched.

I think Voyager I is leaving our solar system on an angle that takes it away from the (relatively) flat plane of planetary and asteroid orbits.

http://physics.uoregon.edu/~jimbrau/BrauImNew/Chap06/7th/AT_...

They're really not that close together. If you were flying through space, you'd have a fairly difficult time determining that you were in an asteroid field when you reached one. Albeit some asteroids do travel in 'families.'

Dr. Marc D. Rayman on the Dawn Project: Dawn will travel 7.7 astronomical units (AU), or nearly 1.2 billion kilometers (almost 720 million miles), to its July 2011 rendezvous with Vesta. Yet in all that time, and across all that distance, the closest the probe will come to a catalogued asteroid is 1.0 million kilometers (greater than 600 thousand miles), or more than 2.5 times the distance between Earth and the moon.

It had a gyroscope that would rotate it to measure magnetic effects in a 360 range, but I believe it was disabled years ago. As far as I know, it's not being controlled. If it was ever manually controlled, the fuel would likely have run out decades ago. Either it got lucky or the engineers ran the calculations to find a clear path.