KH-9, commonly known as Big Bird or KeyHole-9, was a series of photographic reconnaissance satellites launched by the United States between 1971 and 1986. Of twenty launch attempts by the National Reconnaissance Office, all but one were successful. Photographic film aboard the KH-9 was sent back to Earth in recoverable film return capsules for processing and interpretation. The highest ground resolution achieved by the main cameras of the satellite was 2 ft (0.61 m), though another source says "images in the "better-than-one-foot" category" for the last "Gambit" missions.

The National Reconnaissance Office (NRO) is a member of the United States Intelligence Community and an agency of the United States Department of Defense which designs, builds, launches, and operates the reconnaissance satellites of the U.S. federal government. It provides satellite intelligence to several government agencies, particularly signals intelligence (SIGINT) to the NSA, imagery intelligence (IMINT) to the NGA, and measurement and signature intelligence (MASINT) to the DIA. The NRO announced in 2023 that it plans within the following decade to quadruple the number of satellites it operates and increase the number of signals and images it delivers by a factor of ten.