Reconnaissance satellites, first deployed in the early 1960s to peer into denied regions of the Soviet Union and other secretive enemy states, have from time to time been used by civilian agencies of the federal government to assist with mapping, disaster relief, and environmental concerns. There follows a discussion of legal considerations, including whether satellite reconnaissance might constitute a "search" within the meaning of the Fourth Amendment; an overview of statutory authorities, as well as restrictions that might apply; and a brief description of executive branch authorities and Department of Defense directives that might apply. The book concludes by suggesting policy issues Congress may consider as it deliberates the potential advantages and pitfalls that may be encountered in expanding the role of satellite intelligence for homeland security purposes.