Missile Defense Interceptor Hits Target, but Not All Perfect in Test
Boese, Wade, Arms Control Today
MORE THAN A year after the last test of its proposed strategic missile defense system failed, the Pentagon succeeded July 14 in destroying a target warhead in space, though a key radar suffered a software glitch.
Marking the second hit in four attempts, the July 14 test involved launching a modified Minuteman II missile, carrying a mock warhead, from Vandenberg Air Force Base in California toward Hawaii. Approximately 20 minutes after the Minuteman was launched, the Pentagon fired a ground-based interceptor carrying an exoatmospheric kill vehicle (EKV) from the Kwajalein Atoll in the Marshall Islands, more than 7,700 kilometers away. Roughly eight minutes later, the EKV, which is designed to seek out and collide with a target in space, hit the mock warhead some 220 kilometers above Earth with a closing speed of more than 26,000 kilometers per hour, destroying the target.
As in previous intercept tests, the Pentagon knew the target's launch time and trajectory, which was plotted to avoid the more than 8,000 objects in orbit around Earth. The target was also outfitted with a C-band transponder, which sends out a signal precisely identifying the target's location. Data from the transponder was used to formulate the initial intercept plan for launching the booster and EKV because there is no radar available in the test range to track the target early in its flight. However, after it separated from its booster at a distance of about 800 kilometers from the target, the EKV received no data from the transponder.
This latest test essentially repeated the same mission as last year's July intercept attempt, except the Pentagon replaced the single, large balloon decoy that accompanies the mock warhead with a new one, which was more similar to the target than last year's decoy but still markedly different. In last year's test, the EKV did not separate from the booster, preventing an intercept from being attempted. (See ACT, July/August 2000.)
Because that test failed in its early stages, the Pentagon had no opportunity to determine whether the EKV could receive target updates after separating from its booster using data gathered by the prototype Xband radar located at the Kwajalein Atoll. This radar is tasked with tracking and helping to discriminate the target from any decoys. During this last successful intercept attempt, the EKV, which initially orients itself in space by checking its location against various stars, received two in-flight updates after separating from the booster that helped guide it to the target.
After arriving in the approximate area where the intercept was to take place, the EKV used its onboard infrared and visual sensors to seek out the target and discriminate between the target and decoy. The EKV was preprogrammed with information on both objects, including data that the target would be less bright than the decoy. …