The second "hit-to-kill" National Missile Defence (NMD) test on 18 January by the US Ballistic Missile Defense Organization (BMDO) failed in the closing stages because of faulty infrared sensors, according to a preliminary assessment of the $100 million evaluation firing.

A senior US officer says it could take several weeks to pinpoint the reason for the failure, but he says preliminary data indicates that the Raytheon exoatmospheric kill vehicle (EKV) failed to acquire and destroy the re-entry vehicle target when its two infrared sensors malfunctioned. The EKV also has a visible-light sensor, but it is unable to achieve an intercept by itself.

Until the last 6s of the surrogate NMD interceptor's 8min flight from Kwajalein Island Atoll in the central Pacific, all indications were that the EKV would hit the target launched from Vandenberg AFB, California.

All the supporting sensors - the Defense Support Program satellite system, ground-based X-band radar for precision target-tracking and ground-based early warning radars and battle management, command, control and communications (BM/C³) assets- performed as planned. This was the first time these systems have been used with the EKV.

Although disappointed by the results of Integrated Flight Test 4, project officials say setbacks are to be expected as the test flight series gets more complex.

Although no intercept was achieved, "the test helped us learn about collecting and processing target information and getting that information to the kill vehicle to help it conduct the intercept," say project officials.

"This was a real-time test, designed to increase our knowledge and level of confidence with regard to the individual elements, as well as the abilities of those elements to function as a system."

The next NMD test, IFT-5, is set for late April, when the In-Flight Interceptor Communications System (IFICS) will be used for the first time. IFICS provides the link between the BM/C³ and EKV.

Five flight tests are due before US President Bill Clinton decides whether a national anti-ballistic missile system is to be deployed by 2005, for about $13 billion.

Source: Flight International