This book is about spaceborne missions and instruments. In addition, surveys of airborne missions and of campaigns can be found on the accompanying CD-ROM in pdf-format. Compared with the 3rd edition the spaceborne part grew from about 300 to 1000 pages. The complete text - including the electronic-only chapters - contains more than 1900 pages. New chapters treat the history of Earth observation and university missions. The number of commercial Earth imaging missions has grown significantly. A chapter contains reference data and definitions. Extensive appendices provide a comprehensive glossary, acronyms and abbreviations and an index of sensors. An effort has been made to present the information