In December 1993, the space shuttle Endeavour rendezvoused with the Hubble Space Telescope to conduct one of the most high-profile missions of the entire shuttle program. Over the next ten days, the crew of mission STS-61 installed corrective optics to fix the Hubble’s flawed vision, replaced instruments and gyroscopes and solar panels, and sent Hubble off as practically a new telescope.
Twenty years earlier, the secretive National Reconnaissance Office (NRO) that operated America’s fleet of intelligence satellites evaluated the possibility of doing this kind of mission on a regular basis with the largest reconnaissance satellite then in the inventory, the schoolbus-sized HEXAGON.