Figure: A Second Look: Replacing the Wide Field and Planetary Camera

Astronauts remove the Wide Field and Planetary Camera to replace it with its more powerful successor, Wide Field and Planetary Camera 2, during Hubble's first servicing mission in 1993. The camera, shaped something like a grand piano, weighs 277 kg on Earth, but nothing in space. It can detect stars a billion times fainter than the ones we can see with our eyes. Most of Hubble's most popular pictures have been taken with this second camera.

Credit: NASA

http://hubblesite.org/gallery/spacecraft/15/