 Complete the following phrase:  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 