Missile Chaff Decoy
A missile chaff decoy is a countermeasure deployed by ICBMs during their flight to deceive enemy air defense systems. During the re-entry phase, a warhead separates from multiple chaff decoys — lightweight objects designed to produce similar radar returns to the actual warhead — causing enemy interceptor missiles or air defenses to target the decoys rather than the live payload. The chaff and the warhead separate at high altitude, with both continuing on similar trajectories at high velocity.
Role in the Vandenberg Incident
The chaff decoy mechanism is directly relevant to the Vandenberg Air Force Base UFO Film Incident of September 1964. The ICBM test that day was explicitly designed to test this deception capability: a dummy warhead with the exact dimensions and weight of a live nuclear warhead was launched alongside chaff designed to replicate the warhead's radar signature. The purpose was to simulate a real nuclear attack scenario in which Soviet air defenses would target the chaff while the warhead continued to its target.
Lieutenant Robert Jacobs's description of the event notes that the disc-shaped UFO that entered the camera frame appeared to track the dummy warhead specifically — not the chaff — suggesting the craft could distinguish between the actual warhead and its decoys. The warhead was traveling at 6,000–8,000 miles per hour at the fringe of space when the craft fired four directed energy beams at it.
Significance
The chaff decoy design was intended to be the most sophisticated defensive countermeasure available against Soviet anti-ballistic missile systems. That an unknown craft could apparently identify and specifically target the warhead — ignoring the surrounding chaff — implies sensing or identification capabilities significantly beyond the air defense technology of the era.