report burst of data, earlier reports can be at rates no higher than once every 3 to 5 sec until the last 5 to 10 sec before intercept. This is particularly important for the detection of some countermeasures.

8.   Complementing the interceptor capabilities indicated here is a need for enough X-band radars with sufficient acquisition range and capability to observe, image, and measure the dynamics of threat objects over as much of their trajectory as practical to support both discrimination of warheads from other objects and firing solutions and two-way communication for interceptors even in the presence of countermeasures and to perform kill assessment for SLS.

9.   AN/TPY-2 X-band radars forward-based in Japan and in eastern Turkey or Azerbaijan, for example, offer a very important capability, particularly for the defense of allies and deployed U.S. forces, but also for the defense of the United States. Cued by the Defense Support Program (DSP) or the SBIRS, they provide the earliest precision tracks that can be propagated forward in time and used for committing interceptors thousands of kilometers away. They should be appropriately defended against a rollback attack by short-range, short-time-of-flight ballistic or cruise missiles as well as against infiltrating ground attack.

10.   With capable forward-based radars, it is possible for shorter range engagements, where time is not an ally, to commit interceptors shortly after threat burnout. Remaining uncertainties during the interceptor’s boost can be removed by modest divert maneuvers sacrificing little fly-out velocity.

RECOMMENDED GMD EVOLUTION—THE INTERCEPTOR

Overview

As previously noted, the committee’s analysis shows, among other things, that the GMD system does not take advantage of fundamental features long known to maximize effectiveness in a midcourse hit-to-kill defense capability against threats to the U.S. homeland. These features can still be incorporated at a lower overall cost through the recommended GMD-E described here.

In short, the recommended evolutionary GMD-E would provide much longer and more effective concurrent threat observation during engagements by both X-band radars and the onboard sensors of the KV while closing on the threat complex. This combination, coupled with SLS battle space and firing doctrine supported by robust two-way communication, is a powerful tool for discriminating real warheads from countermeasures and for reducing leakage. Precluded in the current GMD architecture, this combination would also provide a more effective U.S. homeland defense capability, albeit still a limited one by virtue of the number of interceptors deployed. Moreover, it would minimize or eliminate the need and cost for so-called early midcourse engagements from Europe-based large interceptors (greater than 4.5 km/sec fly-out velocity).

The recommended GMD-E—a CONUS-based system—takes advantage of



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