NASA Space Flight
The US Air Force’s third Space-Based Infrared System (SBIRS) geosynchronous missile detection satellite will ride to orbit atop United Launch Alliance’s Atlas V rocket Thursday, lifting off from Cape Canaveral Air Force Station during a forty-minute window opening at 19:46 local time (00:46 UTC).
Space-Based Infrared System, or SBIRS, is a system of satellite-mounted sensors operated by the United States Air Force, designed to detect missile launches in order to provide an advance warning of any imminent threat.
The satellites can also perform additional infrared surveillance duties. SBIRS is a successor to the earlier Defense Support Program (DSP), whose twenty-three satellites were launched between 1990 and 2007.
SBIRS uses a combination of dedicated satellites in geosynchronous orbit and instrument packages hosted aboard other satellites in highly elliptical Molniya orbits. The payload of Thursday’s launch, SBIRS-GEO-3, is the third dedicated satellite to launch.
Three hosted, or SBIRS-HEO, payloads are also currently in orbit aboard National Reconnaissance Office signals intelligence spacecraft. A low Earth orbit component to the program was originally planned. However, this was canceled and later evolved into the Space Tracking and Surveillance System (STSS).
The early detection of incoming missiles gives the US military time to react to the threat of a potential nuclear attack, getting key personnel to safety and launching a counterattack. SBIRS also allows missile defense systems to be targeted to intercept the attack.
The SBIRS spacecraft are also tasked with missions described as Technical Intelligence and Battlespace Awareness, using their sensors to identify and analyze the signatures of events producing infrared radiation and to collect data on the conditions of battlefields to aid strategic planning.
The SBIRS program falls under the operation of the US Air Force’s 460th Space Wing, based at Buckley Air Force Base in Colorado.
The United States has operated early warning satellites since the 1960s, beginning with the Missile Defence Alarm System (MIDAS).
The space-based systems augmented ground-based radar systems such as the Ballistic Missile Early Warning System (BMEWS), providing longer range detection which allows missiles to be identified earlier in their flights.
MIDAS was never used operationally; of the first six satellites three were lost to launch failures and the remaining satellites all failed within a day of launch. It was not until MIDAS-7 launched in May 1963 that a missile detection capability could be demonstrated with the satellite tracking various US launches including Atlas, Minuteman, Polaris and Titan missiles.
The operational Defense Support Program (DSP) – originally named Integrated Missile Early Warning System (IMEWS) used geosynchronous satellites in contrast to the low Earth orbit MIDAS. Three generations of DSP satellites were launched – four first-generation spacecraft were launched between 1970 and 1973 using Titan III(23)C rockets.
The second generation, consisting of nine satellites, was deployed between 1976 and 1987; the first six satellites launching atop Titan III(23)C vehicles before its retirement – the final three second-generation spacecraft flew aboard Titan III(34)D/Transtage rockets.
Third-generation DSP satellites were predominantly launched by Titan IV rockets. Exceptions were the third satellite, which was deployed from Space Shuttle Atlantis with the aid of an Inertial Upper Stage (IUS) during 1991’s STS-44 mission, and the final satellite which flew aboard a Delta IV Heavy following the Titan’s retirement.
In total, ten third-generation DSPs were launched, with the first, second and fourth flying aboard the Titan IV(402)A and the Titan IV(402)B being used from the fifth launch onwards. Both of these Titan configurations also made use of an IUS to inject the satellite into geosynchronous orbit.
One of the third-generation satellites, USA-142 – also known as DSP 19, failed to reach its planned orbit as the first and second stages of the Titan IV’s Inertial Upper Stage failed to separate cleanly from each other. The final satellite, USA-197, failed after a few months in service.
The SBIRS program was begun in the 1990s to replace DSP, providing enhanced capabilities. The first satellite, USA-230 or SBIRS-GEO-1, lifted off from Cape Canaveral atop an Atlas V in May 2011. A second satellite, USA-241 or SBIRS-GEO-2, was deployed in March 2013 – also using an Atlas…
