Although combat proven, Global Hawk has yet to pass key tests.

In an upcoming evaluation of the U.S. Air Force Global Hawk reconnaissance unmanned aircraft, testers will determine whether a military system that already has seen extensive combat can pass the rigorous tests the Defense Department, by law, requires before an aircraft can be deployed.

The Global Hawk, which provides field commanders with high resolution and near-real-time imagery of large geographic areas, was deployed to Iraq and Afghanistan, even though the aircraft was still in development. Commanders needed the technology to find targets and gather tactical intelligence.

The Global Hawk will go through a so-called "operational assessment" at Edwards Air Force Base, Calif., in the spring of 2005. The more rigorous "initial operational test and evaluation" will not happen until 2007. IOT&E is considered the "big" report card for a program once it enters full production. It verifies that the system is meeting the specified requirements.

Putting a system that has been in real-world operations through a test program is "highly unusual," said Jay Humphlett, director of strategy and business development at the Raytheon Company, which makes the sensors and ground control stations for the Global Hawk.

However, the Pentagon has a track record of rushing prototype systems to war before they have completed operational testing. A case in point is the Joint Surveillance Target Attack Radar System ground surveillance aircraft. While still in development, JSTARS was deployed to the 1991 Persian Gulf War. The Predator UAV, which, like Global Hawk, began as a demonstration program, was sent to combat in the Balkans in 1999.

Northrop Grumman Corp., the manufacturer of the airframes, so far has delivered 10 Global Hawks to the Air Force--seven prototypes and three production aircraft. The first two production vehicles are at Edwards, while the third was scheduled to be delivered to Beale Air Force Base, in October. Beale, in northern California, is the home base for the Global Hawk.

As the Air Force prepares to test the aircraft, it is wrestling with "how to tailor the operational assessment based on the fact that it's a proven asset," said James J. Hvizd, Raytheon's senior manager for Global Hawk.

"The question is how to get credit because they've been deployed and what do they have to do from scratch in order to have a solid overall operational assessment," he said in an interview.

The tests will measure performance criteria such as range, persistence and sensor control. But most importantly, said Hvizd, the Air Force wants to make sure that the hardware is "production-configured," meaning that it can be manufactured according to specs. That is why the early Global Hawk prototypes are not acceptable in an operational assessment.

"A lot of what will be tested has been tested in combat. It's just a different level of rigor," said Humphlett. "In combat, you are worried about the mission. In tests, you take a look at specific metrics. In combat, you are not going to take the time to measure things, to make sure everything is delivered as advertised."

The Air Force is expected to purchase 51 air vehicles, to be delivered by 2010. The anticipated production rate is approximately six a year, at a cost of $28 million per aircraft, according to Northrop Grumman. The airframe is $18 million a piece, with the sensor package costing $10 million.

Humphlett noted that Raytheon has managed to slash the cost of the sensor suite by about 50 percent, although he would not disclose specific numbers. A Northrop Grumman official said he thought the 50 percent cost reduction is a stretch, "but without benefit of the starting cost and the ending cost, it's difficult to determine."