Much of the story about the U.S. Missile Defense Agency's Airborne Laser (ABL) so far has centered on the missile-killing "big laser," which continues to garner attention whenever it's fired.

Behind the scenes, though, the Beacon Illuminator Laser (BILL), one of the low-power lasers onboard the ABL aircraft, has been a steady and reliable, if unsung, contributor to the directed energy weapon system's performance during ground-based and in-flight tests. As part of ABL's targeting system, BILL has been fired 282 times during recent high-power tests, 49 of which occurred in flight.

This kilowatt-class, illuminator laser is used to measure atmospheric conditions, a critical task that allows compensation for atmospheric turbulence by the beam control / fire control system that points and focuses the high-energy laser's beam on its target with pinpoint accuracy.

Northrop Grumman Corporation designed and developed both the solid-state or electrically powered BILL and the megawatt-class, high-energy chemical laser on ABL.

"BILL helps solve the problem of a laser beam traversing the turbulent atmosphere between the jet aircraft and the target in flight," said Steve Hixson, vice president of Advanced Concepts - Space and Directed Energy Systems for Northrop Grumman's Aerospace Systems sector. "Due in part to BILL, ABL focused a surrogate high-energy laser on a boosting target, showing the incredible precision and maturity of the weapon system's technology."

According to Northrop Grumman ABL Program Manager Guy Renard, "Key to BILL's success has been its ability to maintain consistent power levels throughout ground and in-flight testing. Such stellar performance gives us very high confidence that we have made great strides toward reducing certain risks associated with this revolutionary directed energy weapon system."

The Boeing Company is prime contractor and overall systems integrator for ABL. Lockheed Martin provides the beam control / fire control system.