This book covers the theory and measurement of emission, reflection, temperature, and radiation transfer using the latest advances and techniques, notably the application of Mathcad to radiometric calculations. It also shows classical ways to measure radiometric quantities using only algebra, trigonometry, and basic differential and integral calculus, and provides for the first time the relation between emissivity and temperature error. Included are 26 examples of radiometric calculations ranging from human detection of ballistic missiles and mosquito detection of humans to sidewinder snakes detecting their prey and Sidewinder missiles detecting their targets. Supplemental, executable Mathcad code is available for each application.