The final Shuttle mission to Hubble, Sept. 9, 2009, was to install several new pieces of equipment. This mission's primary scientific priority was the installation of the Wide Field Camera 3 (WFC3) and the Cosmic Origins Spectrograph (COS).
Wide Field Camera 3 has become the power behind studies of dark energy and dark matter, the formation of individual stars and the discovery of extremely remote galaxies previously beyond Hubble's vision. WFC3 sees three different kinds of light: near-ultraviolet, visible and near-infrared, though not simultaneously. The camera's range is much greater than that of the instruments previously aboard.
Astronauts removed Hubble's Wide Field and Planetary Camera 2 (WFPC2) to make room for WFC3. WFC3 has a higher "resolution," or ability to distinguish details, and a larger "field of view," or area the camera is able to see, than WFPC2.
Galaxy evolution, the formation of planets, the rise of the elements needed for life, and the "cosmic web" of gas between galaxies are some of the areas of study for the Cosmic Origins Spectrograph (COS). COS sees exclusively in ultraviolet light and has improved Hubble's ultraviolet sensitivity at least 10 times, and up to 70 times when observing extremely faint objects.
COS took the place of the device installed in Hubble during the first servicing mission to correct Hubble's flawed mirror, the Corrective Optics Space Telescope Axial Replacement (COSTAR). Since the first servicing mission, all of Hubble's replacement instruments have had technology built-in to them to correct Hubble's marred vision, making COSTAR no longer necessary.