Raytheon [RTN] has completed testing of a new passive seeker for the Tomahawk cruise missile designed to find and track frequency emitting targets and guide the missile to them, even as the Navy is looking to wind down production of the missile. 

The testing took place over two days in late April and involved attaching a nosecone for the Navy’s Tomahawk Block IV missiles to a T-39 aircraft to test its ability to seek, identify and track the emitting target.

“Preliminary results look really good and the system is doing what we want it to do,” Roy Donelson, Raytheon’s director for the Tomahawk program, said in an interview. “This is the start in terms of our passive seeker testing, captive carry testing.”

Raytheon is funding the development of the passive seeker and next year intends to integrate it with an active seeker to enhance the Tomahawk’s guidance and targeting capabilities, Donelson said. That work is being done in consultation with the Navy.

Raytheon is already under contract with the Navy to upgrade the warhead, navigation and communications systems for the Tomahawk IVs. Raytheon is also hoping the Navy will embrace deploying the new seekers on the Tomahawks IVs already delivered as well as ones slated for production.

Raytheon has delivered about 3,000 Tomahawks IVs to the Navy and the service has said it has a total inventory of 4,000, including older versions of the Tomahawk.

The Navy, however, has scaled back plans to buy Tomahawks in the next two years as it begins looking to a next-generation sea-based land-attack cruise missile. The Navy has requested funding for 100 Tomahawk Block IVs in fiscal 2015, marking the end of its plans to buy the missiles.

The decision to halt production of a missile that has been a cornerstone of the U.S. arsenal for more than two decades has sparked criticism on Capitol Hill and in other circles. It is launched by cruisers, destroyers and submarines.

Sen. John McCain (R-Ariz.), whose home state produces the Tomahawks, said during a hearing with Navy officials in March that Navy was “rolling the dice” in assuming it could have the new missile in place before the Tomahawk inventory depletes. Navy Secretary Ray Mabus replied that the Navy has begun a study to shape the next generation missile and believes the process would go quick enough to avoid any gaps in the capability.

“We believe we can get that follow-on weapon into the fleet expeditiously,” Mabus said. “We certainly don’t want a gap between the Tomahawk and the next weapon.”

The Navy has said little about what capabilities it is seeking for a next-generation land-attack cruise missile, but thinks it can move faster than the typically cited 10-year period for developing a new missile.

Navy acquisition chief Sean Stackley told lawmakers in March the service could revisit plans to cease Tomahawk production after fiscal 2015 and add the missiles to the budget for the following year if it needed to.

Donelson said Raytheon needs about a two-year lead time on production, and added shutting down the line and re-constituting it later would be costly. He said the Navy is planning to spend $96 million to wind down production.

“The hard part is my lead time is about two years,” he said. “You need an active supply base to do that replenishment, so having a two-to-three year gap would make it very hard to reconstitute the supply base.”