|Names||SBIRS GEO-3 (SV-4)|
Space-Based Infrared System GEOstationary-3 
|Mission type||Infrared early warning|
|Operator||United States Air Force / United States Space Force|
|Mission duration||12 years (planned)|
4 years, 8 months and 27 days (in progress)
|Spacecraft type||SBIRS GEO|
|Manufacturer||Lockheed Martin Space|
|Launch mass||4,500 kg (9,900 lb)|
|Dimensions||15 m x 6.7 m x 6.1 m|
|Start of mission|
|Launch date||21 January 2017, 00:42 UTC|
|Rocket||Atlas V 401 (AV-066)|
|Launch site||Cape Canaveral, SLC-41|
|Contractor||United Launch Alliance|
|Reference system||Geocentric orbit|
|2 SBIRS sensors|
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.
The SBIRS satellites are a replacement for the Defense Support Program (DSP) early warning system. They are intended to detect ballistic missile launches, as well as various other events in the infrared spectrum, including nuclear explosions, aircraft flights, space object entries and reentries, wildfires and spacecraft launches.
The satellite bus consists of a militarized, radiation-hardened satellite, providing power, attitude control, command and control and a communications subsystem with five separate mission data downlinks to meet mission requirements, including system survivability and endurability requirements. SBIRS-GEO 3 was manufactured by Lockheed Martin Space and is built upon the A2100M satellite bus.
The SBIRS sensors are designed to provide greater flexibility and sensitivity than the DSP infrared sensor and detect short-wave and mid-wave infrared signals, allowing SBIRS to perform a broader set of missions. These enhanced capabilities result in improved prediction accuracy for global strategic and tactical warfighters. The on-going evolution of the ground system uses improved mission processing software, resulting in increased event message accuracy and reduced manpower for support and operations of the DSP and SBIRS.
The infrared payload consists of two sensors; a scanner and a step-starer. The scanning sensor continuously scans the Earth to provide 24-7 global strategic missile warning capability. Data from the scanner also contributes to theater and intelligence missions. The step-staring sensor, with its highly-agile and highly-accurate pointing and control system, provides coverage for theater missions and intelligence areas of interest with its fast revisit rates and high sensitivity. SBIRS infrared sensors gather raw, unprocessed data that are down-linked to the ground, so the same radiometric scene observed in space will be available on the ground for processing. The SBIRS sensors also perform on-board signal processing and transmit detected events to the ground, in addition to the unprocessed raw data.