The concern about being hit by space junk brings up the question about the difference in the orbit speeds of the telescope and space craft and the junk that's also in orbit. I heard a report that the junk, of course, is moving at thousands of miles an hour. Isn't everything moving at similar speeds to maintain that orbit?

Are the differences in speeds that significant?

Anybody?

The problem is that the various bits of junk are in orbits with varying inclinations to each other. For example, let's consider two satellites, one which orbits exactly over Earth's equator, and another on an orbit which passes over the poles. The two orbital planes in this case are inclined 90 degrees to each other. If they collide, the speed at which they meet will be enormous.

The enormity of this sort of collision varies by how the orbits' inclinations vary. If they're inclined just 45 degrees, then the relative collision speed will be a lot less than the scenario above (though it'll still be disastrous). As the inclination approaches zero, the collision speed also approaches zero.

Of course, hard collisions can also happen between two objects in the same plane, if their orbits' elliptical eccentricities are different. For instance, consider two satellites in the same plane, one with very low eccentricity (nearly a circle), the other with great eccentricity, a lot more egg-shaped. If these two paths intersect, then a collision will again be at a large relative angle, and the relative speed will be large at that point.

Now, what happens when the shuttle needs to dock with another satellite, such as the ISS or the telescope, is what's called a rendezvous, which means that the shuttle puts itself on an elliptical orbit which just touches the other satellite's orbit, timed so that they'll both be at that point at almost the same instant. When the shuttle gets close, it uses rockets to alter its orbit to match that of the target, so that when they dock it's essentially a collision at a snail's pace.

Well said.

I'm disapointed. I like to read but I'm a visual person. I want to see photo's of said Space Walk

edit:
Stupid me. I just followed the link to the Nasa site that has plenty of amazing pictures

Excellent. Thanks