The SBIRS program was designed to provide a seamless operational transition from DSP to SBIRS and meet jointly-defined requirements of the defense and intelligence communities in support of the missile early warning, missile defense, battlespace awareness and technical intelligence mission areas.[4]
SBIRS GEO-4 was the third geostationary SBIRS satellite to be built, Satellite Vehicle 3 (SV-3). Construction of the satellite was completed before it was required to launch, so the spacecraft was placed into storage. The U.S. Air Force later opted to launch Satellite Vehicle 4 (SV-4) first as SBIRS GEO-3, saving the cost of putting the newly-completed SV-4 into storage and additional testing that would be needed upon taking it back out.[3]
The Atlas V, with the tail number AV-076, flew in its 411 configuration. This Atlas V configuration differs from the 401 version used for the previous three SBIRS GEO launches – which did not use any solid rocket booster (SRB). The change of configuration has ostensibly been made to ensure Centaur can be deorbited after satellite separation, helping to mitigate space debris. On previous SBIRS GEO launches, Centaur has remained in a disposal orbit, close to geostationary transfer orbit (GTO), at the end of its mission.[3]
Launches are separated by dots ( • ), payloads by commas ( , ), multiple names for the same satellite by slashes ( / ). Crewed flights are underlined. Launch failures are marked with the † sign. Payloads deployed from other spacecraft are (enclosed in parentheses).
