Space Shuttle Columbia 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
Hubble Space Telescope shroud of multi-layer insulation keeps the temperature within the telescope stable and surrounds a light aluminum shell in which the telescope and instruments sit. Within the shell, a graphite-epoxy frame keeps the working parts of the telescope firmly aligned. Because graphite composites are hygroscopic, there was a risk that water vapor absorbed by the truss while in Lockheed's clean room would later be expressed in the vacuum of space; resulting in the telescope's instruments being covered by ice. To reduce that risk, a nitrogen gas purge was performed before launching the telescope into space. While construction of the spacecraft in