Abstract: Apparatus (2) for use in operator training with, and the testing and evaluation of, missile detection systems which use infrared sensors which integrate incident energy over a finite time period, which apparatus (2) comprises at least one infrared illumination source (4) for illuminating the sensors, characterised in that the infrared illumination source (4) is a pseudo continuous wave laser infrared illumination source (4) with signal duty and peak power controlled by means of an amplitude, pulse width and pulse repetition interval modulation circuit (8), whereby the laser infrared illumination source (4) operates at shorter repetition intervals than the finite time period so that the laser infrared illumination source (4) appears to the infrared sensors to be a real missile signature.