"Discovery" launched the Hubble Space Telescope and conducted the second and third Hubble service missions. It also launched the "Ulysses" probe and three TDRS satellites. Twice "Discovery" was chosen as the "Return To Flight" Orbiter, first in 1988 after the loss of "Challenger" in 1986, and then again for the twin "Return To Flight" missions in July 2005 and July 2006 after the "Columbia" disaster in 2003. Project Mercury astronaut John Glenn, who was 77 at the time, flew with "Discovery" on STS-95 in 1998, making him the oldest person to go into space.