A new electronics system is being developed to add all weather navigation and attack capabilities to the USAF F-16 aircraft. This system will be mounted under the aircraft in two removable pods, each of which will carry a self-contained environmental control unit (ECU). The extreme mission duty cycle and sophistication of this system results in some unique challenges in the specification and design of this next generation pod mounted ECU package. These include a small high density ECU package, sizing the ECU based on detailed transient performance requirements, and a nontraditional approach to enable the ECU vapor cycle refrigeration system to operate at low ambient temperatures. This paper outlines the ECU requirements, describes the resulting ECU design concepts and configuration, and makes some recommendations for future applications of similar systems.