A comprehensive defense against intercontinental ballistic missiles remains difficult — and perhaps impossible — for several reasons, including the difficulty of achieving “midcourse discrimination” to identify weaponized payloads in a cloud of debris or decoys.
“In the context of missile defense, to discriminate is to distinguish among lethal RVs [reentry vehicles] in mid-course flight that should be targeted by defensive kill vehicles, and non-lethal accompanying objects, whether deliberate countermeasures such as decoys or objects that usually accompany a missile launch, such as booster stage and rocket fuel tanks. Even in the absence of countermeasures, discrimination is still necessary to distinguish RVs from these launch-associated objects.”
“Discrimination of countermeasures is a stringent challenge, because given a reasonable amount of time, money, initiative, and expertise, the offense can (in principle) field countermeasures that the defense cannot handle at any reasonable marginal cost.”
See MDA Discrimination (executive summary), JASON report JSR-10-620, August 3, 2010, released under the Freedom of Information Act on October 3, 2016.
The JASON authors found that the Pentagon’s Missile Defense Agency (MDA) was not well-equipped to address this fundamental problem.
“MDA today has a good record of intercepting RVs, but under conditions that often do not challenge the discrimination capabilities of the missile defense system.”
Even the scope of the discrimination problem is not entirely clear, the JASONs said at the time. “Much remains to be learned about the practical feasibility and effectiveness of countermeasure threats.”
MDA itself “is not agile and flexible, and it may have trouble responding to opponents’ timelines for developing and fielding decoys and other countermeasures,” the JASONs said.
The JASON report recommended that MDA incorporate critical reviews of its programs by independent experts, establish a countermeasures test program through an independent agency, and work more closely with intelligence agencies on analyzing foreign missile threats and countermeasures. It was not immediately clear if the recommendations had been acted upon.