Editor's note: According to a confusing article online at the Washington Examiner: "The cooling system was installed on the Hubble Space Telescope during the STS-95 mission in 1998. That mission, flown by Space Shuttle Discovery, is perhaps best remembered as John Glenn's return to space. The NICMOS cooling system upgrade was intended to provide a longer life than the previous dewar cooling system."
There is one small problem with this story (written by a former NASA PAO employee): STS-95 never visited Hubble. As such, I am not certain how John Glenn or anyone else who was aboard for that mission could have performed any upgrades to Hubble.
Editor's update: They fixed the error - this is what it used to say.