A series of increasingly capable spacecraft were sent to explore the inner planets Venus and Mercury. The history of that planetary exploration is traced in this book along with the evolution of sophisticated spacecraft that unveiled long-sought secrets of the planets. The spacecraft were ingenious and reflected the best efforts of talented people working with the available technology of the day. Additionally, this book showcases engineering involved in those capable machines.A consecutive series of 34 planetary spacecraft, which span the time period 1961 to 2021, are described. This includes the unsuccessful missions of several early spacecraft that paved the way for a better understanding of Venus’ hostile environments. This book will describe many successful spacecraft sent to Venus by the Soviet Union and many successful spacecraft sent to Venus and to Mercury by the United States.The recent exploration of Venus by the European Space Agency’s Venus Express and the Japanese spacecraft Akatsuki can also be found in this book.The author draws on over 50 years of experience on aircraft and spacecraft systems to tell the story of these planetary spacecraft. The spacecraft experience includes being the technical lead for the landing radars on the Surveyor and Apollo lunar landers as well as providing analyses for the rendezvous radar for the Space Shuttle. Practical engineering experience is augmented by Master’s degrees in electrical engineering, physics, and business administration.