A thermal protection system technician takes a measurement of the surface on Atlantis' underside.

In Orbiter Processing Facility-1 at NASA's Kennedy Space Center in Florida, a thermal protection system technician takes a measurement of the surface in the area on space shuttle Atlantis' underside where a heat shield tile will be installed.

The tiles are part of the Orbiter Thermal Protection System that protects the shuttle against temperatures as high as 3,000 degrees Fahrenheit, which are produced during descent for landing. Atlantis is being prepared for the STS-135 mission, which will carry the Raffaello multi-purpose logistics module packed with supplies, logistics and spare parts to the International Space Station. STS-135 is targeted to launch June 28, and will be the last flight for the Space Shuttle Program. Photo credit: NASA/Jack Pfaller