Remote Sensing defined, plus major historical milestones. What are active and passive remote sensing and some examples of each. Then the electromagnetic (EM) spectrum is coverd, showing the atmospheric absorption windows and why instruments are designed to use certain frequencies. An EM wave and how one designs a sensor to measure it. How the EM wave interacts with matter is explained next, noting how different frequencies can behave quite differently. Next is provided an overview of the imaging process and the Remote Sensing value chain.