The book focuses on infrared thermographic NDT systems and approaches. Both principles and engineering practice are covered, with more emphasis on the engineering practice of spacecraft damage detection and analysis. This is achieved by providing an in-depth study of several major topics such as infrared feature extraction, damage reconstruction, reconstructed image fusion, reconstructed image stitching, reconstructed image segmentation, defect positioning, defect edge detection and quantitative calculation. A number of application cases are discussed in detail, including impact damage to single-layer and multi-layer protective configurations, simple impact damage, and complex multi-type impact damage. The comprehensive and systematic treatment of practical problems in infrared detection and spacecraft damage identification is one of the main features of this book, which is particularly suitable for those interested in learning practical solutions in infrared detection technology. This book can benefit researchers, engineers, and graduate students in the fields of aerospace design and manufacturing, spacecraft environmental engineering, and non-destructive testing technology, etc.