The Hubble Space Telescope has revolutionized our understanding of the universe. It has, among many other achievements, revealed thousands of galaxies in what seemed to be empty patches of sky; transformed our knowledge of black holes; found dwarf planets with moons orbiting other stars; and measured precisely how fast the universe is expanding. Here, retired astronaut Kathryn Sullivan describes her work on the NASA team that made all of this possible, recounting how she and other astronauts, engineers, and scientists launched, rescued, repaired, and maintained Hubble, the most productive observatory ever built.
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