Riding a Boeing-built Delta 2 rocket, the global positioning satellite Navstar GPS 2R-12 reached space Wednesday after a successful launch from Florida's Cape Canaveral Air Force Station at 6:54 p.m. EDT (2254 GMT). The spacecraft slid into a transfer orbit 26 minutes later and will replace an aging satellite for the U.S. Air Force.

The successful liftoff was the fourth attempt in a week to launch the 2R-12 spacecraft after three attempts in as many days were scrubbed due to lightning and thunderstorms. In addition to weather delays, the launch also suffered setbacks due to technical glitches with its Delta 2 launch vehicle.

Twice, launch officials had to replace portions of the rocket's first stage. A problematic hydraulic pump was swapped out as a precautionary measure when Boeing engineers became concerned with a similar part of a different Delta 2 rocket, that one set to launch NASA's Aura spacecraft from Vandenberg Air Force Base next month. Later, a vernier engine yaw actuator - which helps keep the rocket on the proper path - was not working properly and had to be replaced.

Built by Lockheed Martin Corp. for the U.S. Air Force, GPS 2R-12 joins a constellation of 24 Block 2 spacecraft providing precise three-dimensional location, elevation, velocity and time services to the U.S. military and civilian customers. The Block 2R spacecraft are designed to cover a broader region of the globe and boost the satellite network's overall performance.

The liftoff of GPS 2R-12 marked the 58^th successful mission for Boeing's Delta 2 launch vehicle. The next Delta 2 launch is set for no earlier than July 8, when it is to carry NASA's Aura satellite into space from Vandenberg Air Force Base in California.