The National Reconnaissance Office (NRO) began in 1961, but operated in secret for decades before it was officially acknowledged. Before the existence was declassified, in 1974, they evaluated numerous incidents where the agency was talked about within the press. The concern was how the Soviets, or the media, would react.
This document was first released to the National Security Archive (also archived below) and was heavily redacted. In August of 2019, I filed a Mandatory Declassification Review (MDR) request to have it reviewed. To my surprise, all redactions were lifted and it was released in full minus one name at the end of the report.
History of NRO Security Breaches, January 7, 1974 [6 Pages, 1MB]