The Spitzer Space Telescope is the final mission in NASA's Great Observatories Program - a family of four space-based observatories, each observing the Universe in a different kind of light. The other missions in the program include the visible-light Hubble Space Telescope (HST), Compton Gamma-Ray Observatory (CGRO), and the Chandra X-Ray Observatory (CXO).
Spitzer is designed to detect infrared radiation, which is primarily heat radiation. It is comprised of two major components:
The Cryogenic Telescope Assembly, which contains the a 85 centimeter telescope and Spitzer's three scientific instruments
The Spacecraft, which controls the telescope, provides power to the instruments, handles the scientific data and communicates with Earth
It may seem like a contradiction, but NASA's Spitzer Space Telescope must be simultaneously warm and cold to function properly. Everything in the Cryogenic Telescope Assembly must be cooled to only a few degrees above absolute zero (-459 degrees Fahrenheit, or -273 degrees Celsius). This is achieved with an onboard tank of liquid helium, or cryogen. Meanwhile, electronic equipment in The Spacecraft portion needs to operate near room temperature.
Spitzer's highly sensitive instruments allow scientists to peer into cosmic regions that are hidden from optical telescopes, including dusty stellar nurseries, the centers of galaxies, and newly forming planetary systems. Spitzer's infrared eyes also allows astronomers see cooler objects in space, like failed stars (brown dwarfs), extrasolar planets, giant molecular clouds, and organic molecules that may hold the secret to life on other planets.
Spitzer was originally built to last for a minimum of 2.5 years, but it lasted in the cold phase for over 5.5 years. On May 15, 2009 the coolant was finally depleted and the Spitzer "warm mission" began. Operating with 2 channels from one of its instruments called IRAC, Spitzer can continue to operate until late in this decade. Check out: Fast Facts and Current Status.