Monitoring the tests: Missile flights and test explosions are watched closely to determine whether an adversary's new weapons might upset the strategic balance

To the naked eye, the tail end of a Soviet missile test high above the Kamchatka Peninsula in northeastern Siberia is almost imperceptible. A cluster of tiny dots of light - the burning nose cones of 10 reentry vehicles - flare briefly as they arch earthward. To the hundreds of millions of dollars' worth of US, Defense Department sensors and computers in the region, the same fleeting event is a gold mine of data on the Soviet missile.