The U.S. Air Force used an Atlas V 401 rocket to launch another Global Positioning System timing and navigation satellite into medium Earth orbit on May 15, replenishing the constellation of 24 spacecraft in a picture-perfect liftoff from Cape Canaveral.

Liftoff of the 3,600-lb. spacecraft came at the opening of its launch window at 5:38 p.m. EDT. The launch vehicle’s Centaur upper stage ignited for the first of two burns — planned to be bounded by a 3-hr. coast phase — at 5:42 p.m. EDT, following burnout and staging of the Atlas common core booster. Final separation of the spacecraft was scheduled at liftoff plus 3-hr., 24 min., according to United Launch Alliance.

Wednesday’s launch marked the first time in almost 28 years that a GPS spacecraft was launched on an Atlas, although prototype spacecraft in the series used Atlas launch vehicles before 1989. In the interim the constellation has been replenished with Delta launch vehicles.

Built by Boeing at its satellite development center in El Segundo, Calif., the new spacecraft is the fourth of 12 in the IIF series that the U.S. Air Force has ordered from the company.

Improvements in the IIF model include a 12-year service life, twice the predicted signal accuracy of its predecessors, reprogrammable on-orbit processing for software uploads, a new L5 signal for better civil aviation applications, and a military “M-code” with better jamming resistance.