A Boeing official says the YAL-1 Airborne Laser (ABL) will seek to pre-empt critics of the programme's first shootdown test scheduled later this year by choosing a deliberately difficult engagement scenario.

Both the first shoot-down attempt and a follow-on test will engage targets simulating the design and trajectory of short range ballistic missile (SRBM), Boeing Michael Rinn told reporters attending a week-long media tour.

To engage a relatively low-altitude SRBM, the 747-400F-based ABL's megawatt-class laser beam must pass through about 100km of atmosphere. Denser atmosphere at lower altitudes can more easily degrade the quality of the laser beam than against longer-range missiles, which reach apogee above the Earth's atmosphere.

"We have chosen one of the most difficult targets," Rinn said. "We have chosen something with a quick burn, very short timelines and atmosphere that we have to correct [the beam] to shoot through."

Rinn said the test scenario was chosen specifically to show that the shootdown attempt was not a "stunt", with the operational conditions tilted artificially in the ABL's favour.

"Having said that there are some things I have deal with," Rinn said. "I have to worry about where I point my laser, how they exit the sky. I have to worry about the FAA and other commercial aircraft So there is a little scripting that goes on."

The ABL programme is also planning to stage a follow-on demonstration soon after the first attempt.

"We think it's important to show the critics that ABL is not a one-shot wonder," Rinn said. "In fact the system is designed to do multiple shots and do them quickly even though we're early in the test programme."

The ABL update comes as the US Department of Defense has released a Fiscal 2010 spending proposal that lowers the programme's status. The DOD budget request confirms plans to delete funding for a second test aircraft, and re-designates the first aircraft as a research and development programme.

However, the first aircraft, dubbed T-1, will continue operating, although with fewer funds.

"We had always planned to fly the T-1 aircraft for a number of years as a test aircraft," Rinn said. "It's not as strong a test programme as I would like, but we will work with our customer to improve what we can do with the dollars available."

Source: FlightGlobal.com