The Advanced Air Defense Electro-Optical Sensor (AADEOS) is an Advanced Technology Demonstration (ATD) Program ground-based Infrared Search and Track (IRST) system intended for use by U.S. Army Forward Area Air Defense (FAAD) units. It is designed to provide automatic detection and tracking of rotary wing and fixed-wing aircraft. The AADEOS has been built and is currently being evaluated at Fort A. P. Hill, Virginia. The evaluation includes collecting IRST video data of military aircraft and background clutter used to train target/clutter discrimination algorithms. The operational performance of the system (i.e., the declaration range and false alarm rate) is being estimated.