ESSA-4 (or TOS-B) was a spin-stabilized operational meteorological satellite. Its name was derived from that of its oversight agency, the Environmental Science Services Administration (ESSA).
ESSA-4 was launched on January 26, 1967 at 17:31 UTC. It was launched atop a Delta rocket from Vandenberg Air Force Base, California, U.S.. The spacecraft had a mass of 285 kilograms (628 lb) at the time of launch. ESSA-4 had an inclination of 102°, and an orbited the earth once every 113.4 minutes. Its perigee was 1,328 kilometers (825 mi) and its apogee was 1,443 kilometers (897 mi).
This article incorporates public domain material from the National Aeronautics and Space Administration document: "ESSA 4". Retrieved June 4, 2018.