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`Thresholds' the key to reducing strategic arms

By Elizabeth PondStaff writer of The Christian Science Monitor / November 12, 1987

Washington and Cambridge, Mass.

The new buzzword is ``thresholds,'' as in ``thresholds list.'' At this point few understand the issue. But it is the linchpin for any reductions in the most threatening nuclear weapons, the strategic monsters.

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The technology and some of the concepts are complicated. The ABCs of it look like this:

What are ``thresholds?''

The Soviets have proposed that the two superpowers define permissible test magnitudes for the coming decade for the various 21st-century technologies needed for ``star wars.'' Anything below a certain brightness of laser or aperture of mirror, they say, could be freely tested on earth or in space. Any tests above these negotiated ``thresholds,'' however, could be conducted only on earth.

What does that have to do with agreeing on the 50 percent cuts in strategic offensive arsenals that President Reagan and Soviet leader Mikhail Gorbachev are aiming for as a top priority?

The Soviets say that they dare not implement deep cuts in offensive weapons unless they are sure that strategic defense (otherwise known as an anti-ballistic missile or ABM system, the Strategic Defense Initiative, SDI, and star wars) will remain limited. Threshold constraints on SDI are the necessary precondition for deep cuts in offensive weapons, they maintain.

Cutting Soviet offensive arsenals when the United States is building a defense would increase instability in a crisis, the Soviets argue, and could be suicidal. If the US goes ahead and deploys strategic defense, the Soviet countermeasure will thus be to increase, and certainly not to decrease, offensive warheads. (The US says it would respond the same way if the Soviet Union deployed strategic defense.)

Therefore, Mr. Gorbachev is signaling Mr. Reagan that either we limit both strategic offense and defense and cooperate in destroying some 10,000 nuclear warheads between us, or we don't limit either defense or offense - and race each other to build another 20,000 warheads in the 1990s.

So that's why the 1972 ABM Treaty prohibited testing or deployment of ABM systems or components in space?

Yes. The intent was to prevent so much development of defensive systems or components that one side could ``break out'' of the treaty with a sudden deployment that would give it decisive military superiority over the other and thereby destabilize the nuclear balance.

But at the same time the treaty allowed enough research and development to be a hedge against breakout by either adversary by letting each side learn enough about new technologies to design countermeasures. But the treaty failed to specify just what constraints would make this distinction in the case of lasers, particle beams, or other ``exotic'' technologies that were only dimly perceived 15 years ago. This gap is what a thresholds list would seek to fill.

But would setting test thresholds kill Mr. Reagan's SDI program?

The most ardent fans of SDI say it would. The most ardent fans of arms control say it would not - and so do pragmatists who stand in the middle and support SDI research and the ABM Treaty.

The clearest example, according to one US official familiar with the Soviet list, is the Soviets' proposed ``restriction'' of kinetic kill experiments in space to velocities of 5 miles per second, achievable from satellites in low-earth orbits. With one satellite traveling 5 miles per second in one direction, and another traveling 5 miles per second in the opposite direction, and with further modification possible by changing the orbital plane, tests could be determined for any impact speed up to 13 miles per second - a velocity much greater than is needed for any SDI experiments planned over the next decade.

Moreover, Soviet negotiators have said this specification would in effect confer Soviet legitimation on such American SDI testing in space.