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out the gyroscopes needed for pointing control. When a premature loss of solid-nitrogen coolant cut short NICMOS’s
operational life, engineers devised innovative mechanical refrigeration technology as an alternate way of cooling its detectors
to their operating temperature of –320°F (–196°C). On Servicing Mission 3B in 2002, this cooling system was retrofitted to

NICMOS, which brought the instrument back to life. During that mission, astronauts also replaced the productive, but aging,
ESA-built Faint Object Camera with a new, more powerful camera—the Advanced Camera for Surveys (ACS)—providing a
tenfold improvement over WFPC2.

Servicing Mission 4 (SM4), the final servicing mission to Hubble in 2009, brought the telescope to the apex of its
scientific capabilities. Astronauts installed two new instruments: the Cosmic Origins Spectrograph (COS) and the Wide
Field Camera 3 (WFC3). COS is the most sensitive ultraviolet spectrograph ever built for Hubble. It probes the cosmic

web, the large-scale structure of the universe, whose form is determined by the gravity of dark matter and is traced by
the spatial distribution of galaxies and intergalactic gas. WFC3 is sensitive across a wide range of wavelengths (colors)

Positioned on the remote manipulator system, astronaut Mike Good transports the assortment of tools required to repair the Space Telescope Imaging
Spectrograph during Servicing Mission 4. Included among them is the ingenious fastener capture plate (blue rectangular device floating above him) that
would be used to trap more than 100 non-captive screws during removal of the instrument’s electronics cover.

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