Abstract: A radiometric countermeasures system installable on a military tank to det a passive millimeter wave sensor in a guidance system on an enemy missile. The system comprises an oscillator source of mm waves; a variable attenuator connected to the oscillator to adjust the power level of the oscillator output signal; a circular polarizer connected to the attenuator; an antenna connected to the polarizer to broadcast mm wave radiation to the ambient atmosphere in which the military tank is located; and means for adjusting the attenuation of the attenuator such that total mm wave emission from the tank and from the antenna is substantially equal to the naturally-occurring mm wave radiation emitted by the background scenery in the vicinity of the tank.