1993 STS-61: Astronauts replaced Hubble’s original Wide Field/Planetary Camera with WFPC-2, built to correct the telescope’s faulty optics.
1993 STS-61: The photometer they removed weighed 221 kilograms, making room for the optics-correction device COSTAR.
1993 STS-61: A deformed compartment door nearly jeopardized the EVA; astronauts worked its top and bottom from different positions to close it.
1997 STS-82: Replacing a Solar Array Drive Electronics unit meant handling bolts and connectors not designed for replacement during a spacewalk.
1997 STS-82: Astronauts patched only selected damaged insulation areas because their supply of repair blankets was limited, leaving other areas for later servicing.