Missile test sets require a standard against which they can be calibrated and compared. A transfer radiometer has been developed for this purpose. This radiometer is calibrated against a primary standard and becomes a secondary calibration standard which is used by replacing the missile in the test stand. The transfer radiometer is fully compatible with the test set from the aspects of mechanical, radiometric, optical, electronic and total system adaptation and can be considered as a black box which engineering and technician specialists can use with ease without comprehending its internal operation. The paper describes the concepts and operation of the transfer radiometer and its method of use.