GPS Block IIF-4 Launch Set for May 15
>
http://www.gpsworld.com/gps-block-iif-4-launch-set-may-15/
> The next GPS satellite launch is scheduled for May 15 with the launch
> window extending from 21:39 to 21:58 UTC. An Atlas 5 rocket will be
> used to place the satellite, GPS IIF-4, into orbit from Cape
> Canaveral Air Force Station.
> This is the first time in almost 28 years that an Atlas rocket will
> be used to launch a GPS satellite. All of the prototype or Block I
> satellites were orbited with Atlas rockets. Since then, Delta rockets
> have been used exclusively for GPS launches. The IIF satellites are
> being launched with a mixture of Atlas and Delta rockets.
> The IIF-4 satellite, also known as SVN66, will operate as PRN27.
> SVN66/PRN27 will eventually occupy the C-2 slot, replacing
> SVN33/PRN03, a Block IIA satellite launched in 1996. Reportedly,
> SVN66/PRN27 will go through an extended period of testing following
> launch, and is not expected to be set healthy until August. SVN33
> will become a reserve or backup satellite.