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Named for astronomer Edwin Hubble and launched into orbit in 1990, the Hubble Space Telescope is exactly that: an optical telescope that's also an orbiting satellite. There have been a variety of space telescopes before, but the Hubble is the largest optical telescope ever put into orbit.
- The main advantages of the Hubble relative to ground-based satellites are to be found in its orbital environment. Ground-based telescopes must deal with the distortion caused by the atmosphere and background light. Neither of these is an issue for the Hubble.
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Servicing the HubbleThe optical telescope on the Hubble is a Cassegrain Reflector. In this design, light is initially collected by a primary parabolic mirror. It's reflected to a hyperbolic convex mirror. It should then finally reflected through a hole in the primary mirror to the "eyepiece." However, the mirrors were designed to the very high specification necessary to operate in the UV range, as well as visible light.
Like most satellites, the Hubble uses a combination of on-board gyroscopes and thrusters to maintain and alter its position in orbit.
The telescope also carries a number of on-board instruments, and these have been changed by Space Shuttle servicing missions over time. The 2008 payload consisted of the the Advanced Camera for Surveys; the Cosmic Origins Spectrograph; the Multi-Object Spectrometer; the Near Infrared Camera; the Space Telescope Imaging Spectrograph; and the Wide Field Camera version 3.
