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Hubble Space Telescope
Run from the Space Telescope Science Institute in Baltimore, but operated from the Goddard space centre, the Hubble Space Telescope is an orbital optical telescope which has already revolutionised our understanding of the universe.
Named for Edwin Hubble, it was launched into an orbit 300 miles up, and is designed to be serviced in space, it has surpassed the design aims, but it is better know to laymen for its many technical problems.
Probably the best known problem is with the mirror. They commissioned 2 different mirrors, specifically to make sure that there was not a problem with the satellite because of the mirror.
Unfortunately, while they were both delivered, they made a classic ISO9002 process error, and didn't check the final product, only the process. The result was that while one mirror was completely perfect, the other was made precisely wrong.
Obviously, this faulty mirror was the one installed, a fact not discovered until after launch, and about the only component they could not repair in space.
This in turn had the effect of making the image very blurred due to the edges and the centre focusing at different points. However the precision of the mirror had the side effect of making it fairly easy to create a computer filtering program to extract clean images from the distorted images. It also made the design of the COSTAR module easier.
COSTAR stands for Corrective Optics Space Telescope Axial Replacement, and it replaced the high speed photometer during the maintenance shuttle mission and optically error corrects the images, making the images 10 times better than any ground based images.
The mission also fixed a problem with the pointing, due to jitter from the solar panels being too flexible under thermal expansion, and a couple of dodgy gyroscopes. It also replaced the wide field and planetary camera with an improved model, which contains its own corrective optics.
The results from the first 3 years before the maintenance mission helped to shed new light on black holes, planetary nebula, supernova, proto-planetary discs and galactic evolution. Also planetary result show voyager quality images of storms on Saturn, and others of Mars and Io.
It also helped get a better value for the Hubble constant by imaging ic4182, which contains both a supernova (well studied since 1937) and Cepheid variables. It gives a value of 51kps/megaparsec, giving an age for the universe of 15-17 billion years old.
After the servicing, the results got even better, proving the concept of space based telescopes.