Counterattack. U.S. defense officials say they have a new technical strategy for spotting enemy missiles.

Shooting Down a Missile Defense Test

Much of the data from a 1997 ballistic missile test labeled a solid success have software and sensor problems that may render them useless, say sources familiar with an investigation by the General Accounting Office (GAO). The wording of the two reports is still being fiercely debated, but their upcoming release is sure to provide more ammunition for skeptics of the controversial ballistic missile defense program.

In the 24 June 1997 test, a rocket carrying an infrared sensor was launched from Meck Island in the Pacific to determine whether it could discriminate among nine objects launched from the California coast--a step toward distinguishing between enemy warheads and decoys. Department of Defense program manager Joseph Cosumano declared that "all aspects" of the $100 million test "were highly successful." But many disputed that conclusion, including Theodore Postol, a physicist at the Massachusetts Institute of Technology (MIT), who argues that the tests' flaws were covered up. The performance of the sensor is the latest in a long line of complaints about the way the test was prepared, conducted, and analyzed. This ongoing debate prompted bipartisan legislative requests for studies by GAO, Congress's investigative arm.

The GAO report uncovered a problem with the sensors that was never mentioned in unclassified materials, government officials say. A key component of the 1997 test was the focal plane array used to detect infrared wavelengths from the targets. The resulting data were key to determining whether an object was a warhead or a decoy. The sensor was calibrated to function best at 10 kelvin, but during the test the sensor temperature dropped only to an estimated 13 K, which would lessen its accuracy. Controllers tried to recalibrate the instrument in midflight, but "there was a tremendous amount of noise" in the resulting data, says one government engineer familiar with the test results. GAO's Robert Levin confirmed that the sensor's performance lies at the heart of the reports, but he declined further comment.

Keith Englander, deputy for system engineering and integration at the Pentagon's newly redesignated Missile Defense Agency, declined to discuss technical details of the 1997 test. However, he says that discriminating between decoys and warheads "is hard," that the methods used in the test to analyze that discrimination "were fragile," and that the sensors "did not have as robust a discrimination method" as the sensor that has replaced it.