
Viewed from the roof of the 525-foot Vehicle Assembly Building (VAB), Shuttle Discovery approaches runway 33 at Kennedy Space Center, Cape Canaveral, Florida, USA 20 April 2010. Discovery touched down at 9:08am edt to complete a 15-day mission deliver supplies and spare parts to the International Space Station (ISS). EPA/JUSTIN DERNIER

Viewed from the roof of the 525-foot Vehicle Assembly Building (VAB), Shuttle Discovery approaches runway 33 at Kennedy Space Center, Cape Canaveral, Florida, USA 20 April 2010. Discovery touched down at 9:08am edt to complete a 15-day mission deliver supplies and spare parts to the International Space Station (ISS). EPA/JUSTIN DERNIER

Space Shuttle Discovery lands at the shuttle landing facility, Kennedy Space Center, Cape Canaveral, Florida, USA, 20 April 2010. Shuttle Discovery completed a fifteen day mission landing at 9:08 a.m. est. There are now only three shuttle launches and landings left in the shuttle program. EPA/GARY I ROTHSTEIN

Space Shuttle Discovery lands at the shuttle landing facility, Kennedy Space Center, Cape Canaveral, Florida, USA, 20 April 2010. Shuttle Discovery completed a fifteen day mission landing at 9:08 a.m. est. There are now only three shuttle launches and landings left in the shuttle program. EPA/GARY I ROTHSTEIN

Space Shuttle Discovery lands at the shuttle landing facility, Kennedy Space Center, Cape Canaveral, Florida, USA, 20 April 2010. Shuttle Discovery completed a fifteen day mission landing at 9:08 a.m. est. There are now only three shuttle launches and landings left in the shuttle program. EPA/GARY I ROTHSTEIN