The ESSA series was the second generation of US meterological satellites after the TIROS (Television & Infra-Red Observation Satellite) series. They were also called OT (Operational TIROS), TOS (TIROS Operational Satellite).

American orbital launch vehicle family with Thor first stage and a delta second stage.

The United States Air Force (USAF) is the air service branch of the United States Armed Forces, and is one of the eight uniformed services of the United States. Originally created on 1 August 1907, as a part of the United States Army Signal Corps, the USAF was established as a separate branch of the United States Armed Forces in 1947 with the enactment of the National Security Act of 1947.