Hubble Space Telescope (1990)

Launched in 1990 and serviced by astronauts on 5 Space Shuttle missions, the Hubble Space Telescope has made over 1.5 million observations, helped determine the expansion rate of the universe (the Hubble Constant), confirmed the existence of dark energy, and produced images that have become cultural icons. It has enabled over 19,000 scientific papers and fundamentally transformed our understanding of galaxy formation, black holes, and the age of the universe.