A tugboat escorts as it tows the right spent booster from space shuttle Atlantis' final to Port Canaveral.

A water-spraying tugboat escorts the Liberty Star as it tows the right spent booster from space shuttle Atlantis' final to Port Canaveral in Florida. The Liberty Star is one of NASA's solid rocket booster retrieval ships. The shuttle's two solid rocket booster casings and associated flight hardware are recovered in the Atlantic Ocean after every launch by Freedom Star and Liberty Star. The boosters impact the Atlantic about seven minutes after liftoff and the retrieval ships are stationed about 10 miles from the impact area at the time of splashdown. After the spent segments are processed, they will be transported to Utah, where they will be deserviced and stored, if needed. Atlantis began its final flight at 11:29 a.m. EDT on July 8 to deliver the Raffaello multi-purpose logistics module packed with supplies and spare parts for the International Space Station. Atlantis also delivers the Robotic Refueling Mission experiment that will investigate the potential for robotically refueling existing satellites in orbit to the station. In addition, Atlantis will return with a failed ammonia pump module to help NASA better understand the failure mechanism and improve pump designs for future systems. STS-135 is the 33rd flight of Atlantis, the 37th shuttle mission to the space station, and the 135th and final mission of NASA's Space Shuttle Program. For more information, visit www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts135/index.html. Photo credit: NASA/Kim Shiflett