Hubble Space Telescope

Deployed in 1990, Hubble Space Telescope has delivered over 1.4 million observations, reshaping cosmology from measuring the universe's expansion rate to imaging the deepest galaxies. Its 1994 repair mission saw astronauts replace instruments at a cost of $1.9 billion, extending operations by 15 years. Hubble is 30% cheaper per year than the typical space telescope, yet it outperforms #4 James Webb Space Telescope in ultraviolet observation with sensitivity to wavelengths down to 115 nanometers.