How can you be sure the high explosive implosion system of a nuclear warhead will work after sitting in a silo for years and then being lobbed toward its target by an intercontinental ballistic missile? Well, how about replacing the plutonium pit of the weapon with a telemetry package that receives data from sensors embedded in the high explosives and radios out information about the approaching detonation wave before it arrives and crushes the electronics into oblivion!
Here is an article in the March/April 2003 issue of Los Alamos National Laboratory’s Nuclear Weapons Journal, “High-Explosive Radio Telemetry” [PDF, pages 2 and 3], that describes how it’s done. This paper, “Radio Frequency Overview of the High Explosive Radio Telemetry Project” [PDF] has details of how the information is received, encoded, and transmitted in the 20 microseconds before the device is destroyed.