The Spitzer Space Telescope is a space-based infrared observatory launched in 2003. It is the fourth and final of the NASA Great Observatories program. The telescope is named after astronomer Lyman Spitzer, who proposed the concept of space telescopes in 1946. Its mission is to study objects in the universe that emit infrared radiation, such as stars, galaxies, and interstellar dust clouds. The telescope has made many discoveries, including the detection of water vapor on extrasolar planets and the identification of new classes of stars and galaxies. It has also been used to study star formation, supermassive black holes, and dark matter.