The United States has detected what appears to be a major new Soviet arms violation on the eve of the summit meeting between President Reagan and Soviet leader Mikhail Gorbachev.
According to a government defense expert, U.S. intelligence services have discovered that the Soviets have deployed a combination of mobile SA-X-12 surface-to-air missiles (SAMs) and mobile "Griddle Pan" radar systems to protect newly deployed SS-25 mobile intercontinental ballistic missiles.
Some experts within the administration say the combination of mobile SAM missiles, mobile radars and mobile ICBMs can be viewed only as a mobile anti-ballistic missile defense system.
By itself, the deployment of the SA-X-12 as an anti-aircraft system is not new. But its deployment in the same area as ICBMs could provide the first concrete indication of it being used to defend missiles in violation of the 1972 ABM treaty.
U.S. officials are concerned about the development of a separate interceptor missile [------CUT OFF LINES--------] defensive capability against medium-range and submarine-launched ballistic missiles. Such a system would violate the 1972 ABM treaty, which limits each country to one fixed ABM system at one location. The Soviets already have an updated ABM system defending Moscow.
"You don't defend mobile ICBMs against bomber and cruise missile attacks," one defense expert said. "The ICBMs would be long gone before bombers or cruise missiles got there. A mobile SAM plus a mobile ICBM equals a mobile ABM system."
The United States has no system for defending against Soviet ballistic missiles, although the administration's proposed space-based Strategic Defense Initiative foresees such a defense.
The significance of a Soviet mobile ABM system, if it does exist, is that it would permit the Soviets to launch a first strike from their large inventory of fixed silo-based ICBMs and then be relatively sure their mobile reserve missiles would be immune from a U.S. counterattack, according to one expert.
"The Soviets have developed an invulnerable second-strike capability on top of an overwhelming first-strike capability," he said. "Once this is all fully operational in large numbers, the U.S. deterrence is gone."
That could happen, he said, "by this time next year."
Despite elaborate Soviet efforts to camouflage and conceal the new deployments, the expert said, U.S. intelligence services have detected them at several of the five existing SS-25 sites.
It is assumed, but not yet proven, that the mobile missiles and radars have been deployed at all five of the existing SS-25 sites at Yoshkarola, Yurya, Shadrinski, Novosibirsk and Omsk. Each base houses nine ICBMs, and the Soviets plan to have a total of 20 bases, a source said.
Critics of the arms-control agreements have argued that the Soviets have been moving for some time toward a nationwide ABM system, pointing to Soviet development of a large "battle management" radar near Krasnoyarsk in Siberia.
Such a radar is a key link in a nationwide ABM system, since it has the task of detecting, sorting out and tracking swarms of incoming missiles. That information would be passed through a control center to defense sites, such as those now apparently deployed at the SS-25 bases.
According to an unclassified Defense Department publication on Soviet military power, "The Soviets are continuing to deploy improved air surveillance data systems that can rapidly pass data from outlying radars through the air-surveillance network to ground-controlled intercept sites and SAM command posts."
The Griddle Pan radars would take over once incoming missiles were within the 100-kilometer range of SA-X-12 ground-to-air missiles.
The Soviets and some supporters of the ABM treaty have argued that the Krasnoyarsk radar is not such a battle-management radar. But the Soviets also have offered to stop work on the site in exchange for the U.S. giving up modernization of two air-defense radars -- one in England, the other in Greenland.
Sources also claim that Soviet development of the Griddle Pan radar and SA-X-12 combination, even without deployment, violated the ABM treaty. The treaty and several interpretive accords bar testing of SAM missiles and ABM components, such as the Griddle Pan radars, together.
Thus, technically, the Soviets were barred from testing the Griddle Pan radars and the SA-X-12 missiles against incoming ICBMs.
But interpretations signed by both sides permit the radars to be used at any time to test their range or when aircraft are in the area. To test the combination together and stay within the letter of agreements, the Soviets needed only to claim that an aircraft was in the area at the same time as a test ICBM.
"We were begging them to lie to us, and the Griddle Pan and the SS-A-12 have been tested repeatedly in the ABM mode," the defense expert said. "They have been tested many different ways against ballistic missile re-entry vehicles. ... The Soviets have got great confidence in this combination."