This classic opens with a history of the development of the infrared portion of the spectrum, probes the system engineering process, and then examines the characteristics of the successful system engineer. The next eleven chapters delve deeply into the elements of infrared technology. Chapter 13 explains the functional relationships between the various system elements and the effects of their interactions when assembled into a system. In Chapter 14 the reader is invited to watch the development of an infrared search system for commercial jet transports. Part II contains an in-depth treatment of the applications of infrared techniques to the solution of military, industrial, medical, and scientific problems. It contains nearly 1400 annotated references to the infrared literature of the world. The annotations summarize the content, describe the hardware, details its performance and examine the significant results. The references are carefully arranged, extensively indexed, and does not contain citations to the classified or report literature, a feature appreciated by most readers. For those readers having the necessary credentials, Appendix 4 is a guide to the unpublished and classified literature of the infrared.