The ULA press release about the launch describes the mission:

The Space Based Infrared System is considered one of the nation’s highest priority space programs and is designed to provide global, persistent, infrared surveillance capabilities to meet 21st century demands in four national security mission areas:

Missile Warning
Reliable, unambiguous, timely and accurate warning for theater and strategic missile launches.

Missile Defense
Delivery of critical information supporting the effective operation of missile defense systems.

Technical Intelligence
Ability to characterize infrared (IR) event signatures, phenomenology and threat performance data.

Battlespace Awareness
Delivery of comprehensive IR data to help characterize battlespace conditions.

The SBIRS team is led by the Remote Sensing Systems Directorate at the U.S. Air Force Space and Missile Systems Center. Lockheed Martin is the prime contractor, with Northrop Grumman as the payload integrator. Air Force Space Command operates the SBIRS system.