Replacing the Raytheon AGM-88E High-speed Anti-Radiation Missile (HARM) with a more accurate and versatile weapon is gaining fresh interest from the US Air Force.

With the US Navy poised to deploy the Advanced Anti-Radiation Guided Missile (AARGM) as soon as next year, the USAF is favouring adopting a separate, two-tiered programme to replace HARM. The first step focuses on introducing an improved version developed by Raytheon that corrects for HARM's known deficiencies and expands its mission set to engage any time critical target.

For the longer term, the air force has initiated early design work to develop a so-called joint dual-role air-to-air dominance missile, which seeks to replace both the HARM and Raytheon's AIM-120 Amraam.

In May, Boeing received the first contract worth $4.2 million to develop propulsion and control technologies for the new missile, says Advanced Systems president George Muellner.

Although Boeing lacks experience in the air-to-air missile market, the company is not ruling out a prime contractor role in the programme, Muellner says. Other known rivals include Lockheed Martin, Northrop Grumman and Raytheon.

The 1970's-era HARM is designed to lock-on to a hostile radar emitter, but the missile's accuracy can vary wildly if the targeted radar is switched off or placed in stand-by mode. More disturbingly, the missile continues to scan for emitters, increasing the risk of fratricide if friendly forces are also operating ground radars nearby.

In the near-term, the USAF intends to move forward with a HARM upgrade. Raytheon's so-called "HDAM" proposal is included in a list of unfunded requirements submitted to the US Congress in hopes of obtaining sponsorship. No progress on Capitol Hill is expected this year, but the requirement remains an issue.

"The air force is still working, trying to get us into production," Raytheon says.

The HDAM is a spin-off of a three-nation effort called precision navigation upgrade, which the USN cancelled several years ago to focus on AARGM. The upgrade adds an inertial measurement unit and GPS capability for navigation, as well as software that prevents the weapon from targeting emitters in specified areas.