Had Columbia not been destroyed, it would have been fitted with the external airlock/docking adapter for STS-118, an International Space Station assembly mission, originally planned for November 2003.
Columbia was scheduled for this mission due to Discovery being out of service for its Orbital Major Modification, and because the ISS assembly schedule could not be adhered to with only Endeavour and Atlantis.

Columbia's 'career' would have started to wind down after STS-118.
It was to service the Hubble Space Telescope two more times between 2004 and 2005, but no more missions were planned for it again except for a mission designated STS-144 where it would retrieve the Hubble Space Telescope from orbit and bring it back to Earth.
Following the Columbia accident, NASA flew the STS-125 mission using Atlantis, combining the planned fourth and fifth servicing missions into one final mission to Hubble.
Because of the retirement of the Space Shuttle fleet, the batteries and gyroscopes that keep the telescope pointed will eventually fail also because of the magnifier screen, which would result in its reentry and break-up in Earth's atmosphere.
 A "Soft Capture Docking Mechanism", based on the docking adapter that was to be used on the Orion spacecraft, was installed during the last servicing mission in anticipation of this event.

Columbia was also scheduled to launch the X-38 V-201 Crew Return Vehicle prototype as the next mission after STS-118, until the cancellation of the project in 2002.
Had Columbia not been destroyed, it would have been fitted with the external airlock/docking adapter for STS-118, an International Space Station assembly mission, originally planned for November 2003. Columbia was scheduled for this mission due to Discovery being out of service for its Orbital Major Modification, and because the ISS assembly schedule could not be adhered to with only Endeavour and Atlantis.
Columbia's 'career' would have started to wind down after STS-118. It was to service the Hubble Space Telescope two more times between 2004 and 2005, but no more missions were planned for it again except for a mission designated STS-144 where it would retrieve the Hubble Space Telescope from orbit and bring it back to Earth. Following the Columbia accident, NASA flew the STS-125 mission using Atlantis, combining the planned fourth and fifth servicing missions into one final mission to Hubble. Because of the retirement of the Space Shuttle fleet, the batteries and gyroscopes that keep the telescope pointed will eventually fail also because of the magnifier screen, which would result in its reentry and break-up in Earth's atmosphere.  A "Soft Capture Docking Mechanism", based on the docking adapter that was to be used on the Orion spacecraft, was installed during the last servicing mission in anticipation of this event.
Columbia was also scheduled to launch the X-38 V-201 Crew Return Vehicle prototype as the next mission after STS-118, until the cancellation of the project in 2002.
Space Shuttle Columbia