minal trajectories. Shorter range threats have burn times too short and burnout altitudes too low to engage before their midcourse or terminal phase of flight.

2.   In the view of this committee and based on 50 years of knowledge and experience with ballistic missiles and defense against them, midcourse defense with a terminal underlay where needed would be the most cost-effective defense against ballistic missiles. Among its other benefits, midcourse has time on its side, and this time should be used wisely.

3.   When carefully examined, early intercept is not early enough to avoid the issues of midcourse discrimination, and it reduces the time available for viewing, which is so important for midcourse discrimination. Moreover, the schemes recommended to circumvent that problem are vulnerable to the deployment scheme chosen by the attacker. However, early intercepts do sometimes offer additional shot opportunities and might also constrain an adversary’s payload deployment time, making effective countermeasures potentially more difficult.

4.   It should therefore be recognized that no practical defense scheme can avoid the need for midcourse discrimination. Until that reality is acknowledged, there will be no end to poorly thought out schemes proposing to avoid the need for midcourse discrimination.

5.   Whether decoys can be readily discriminated, particularly in the face of antisimulation techniques, remains a contentious subject however. The combination of observations for more than 100 sec by an interceptor-mounted optical sensor that is closing on the threat complex, together with concurrent X-band radar observations and a firing doctrine that exploits the battle space available for SLS engagements, offers the greatest probability of being able to separate real threatening objects from decoys and other objects and should be central to any defense of the U.S. homeland, allies and friends, and U.S. deployed forces.

6.   To effectively exploit these capabilities, interceptors must be within sight of a radar—not necessarily the same one—in order for the radar to communicate with the interceptor at any time from shortly after launch until intercept. This means that while tracking the interceptor and target, the radar(s) must be able to transmit in-flight updates based on radar or battle manager observations and to receive and relay downlinks from the interceptor once its sensor is uncapped and it sees and decides to engage. The interceptor then must have the ability to receive communication uplinks at any time after its first stage burns out (except during staging events) and to send down to the battle manager, via the radar data on its observation of the threat any time after sensor uncap, its decisions about ranking and which object it selects to intercept.

7.   The observed and processed data transmitted from a midcourse interceptor should include processed focal plane data as well as all object track files and their ranking for use by the battle manager for second-shot decisions. It is expected that the focal plane will be read out at a rate of at least 50 Hz and that the final image messages should be at a rate of at least 3 Hz within 0.5 sec of intercept. While it is recognized that this may dictate high bit rates in the last



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement