The ionosphere is a layer of the Earth's atmosphere that extends from about 50 km to 1000 km above the Earth's surface. It is ionized by solar radiation, which creates ions and free electrons in the upper atmosphere. These ions and electrons reflect radio waves back to the Earth's surface, allowing long-distance radio communication as well as absorption of harmful solar radiation. Ionospheric conductivity monitoring assesses the state of the ionosphere and improves the accuracy of satellite communications. This book is organized into two sections on the influence and impact of transient or orbiting humanmade objects into the ionosphere and the monitoring and modeling of the temporal evolution of the ionosphere. The information presented will lead to a better understanding and forecasting of the ionosphere’s dynamic.