Earth’s atmosphere distort the view of telescopes on the ground. This is why our stars look twinkle on the night’s sky. To see the planets and stars clearly is by placing the telescope beyond the atmosphere. Hubble telescope is 569 km above the surface of Earth and gives the clear picture of things in the space.
Every 97 minutes, Hubble completes a spin around Earth, moving at the speed of about five miles per second (8 km per second) — fast enough to travel across the United States in about 10 minutes. As it travels, Hubble’s mirror captures light and directs it into its several science instruments
(ref: http://hubblesite.org/the_telescope/hubble_essentials/)