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 The Environmental Science Services Administration (ESSA) was a United States federal government, United States Federal executive agency created in 1965 as part of a reorganization of the United States Department of Commerce.

(ESSA).

Background

ESSA 4 was launched to replace ESSA 2, launched February 3, 1966, which had drifted into an orbit of limited usefulness. The satellite was financed, managed, and operated by the

(ESSA).

Spacecraft

The cartwheel-shaped spacecraft carried two Automatic Picture Transmission (APT) systems, with which it could instantly transmit photos of Earth's cloudcover to APT ground stations.

Launch

ESSA-4 was launched on January 26, 1967, at 17:31

UTC Coordinated Universal Time (UTC) is the primary time standard globally used to regulate clocks and time. It establishes a reference for the current time, forming the basis for civil time and time zones. UTC facilitates international communica ...

. It was launched atop a

Delta Delta commonly refers to: * Delta (letter) (Δ or δ), the fourth letter of the Greek alphabet * D (NATO phonetic alphabet: "Delta"), the fourth letter in the Latin alphabet * River delta, at a river mouth * Delta Air Lines, a major US carrier ...

rocket from

Vandenberg Space Launch Complex 2 Space Launch Complex 2 (SLC-2) is an active rocket launch site at Vandenberg Space Force Base, in California, United States, USA. It consists of two launch pads: Space Launch Complex 2 East (SLC-2E, originally LC 75-1-1), used by the PGM-17 Thor ...

, into

Sun-synchronous orbit A Sun-synchronous orbit (SSO), also called a heliosynchronous orbit, is a nearly polar orbit around a planet, in which the satellite passes over any given point of the planet's surface at the same local mean solar time. More technically, it is ...

. ESSA-4 had an inclination of 102°, and an orbited the Earth once every 113.4 minutes. Its

perigee An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides perta ...

was and its

apogee An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides perta ...

was . The satellite properly aligned itself with respect to the Earth during its 18th orbit, whereupon its first photos were transmitted. A two-week spacecraft checkout and evaluation program ensued. One of the APTs failed after launch, but the other performed normally.

Legacy and status

ESSA 4 was turned operationally off on December 6, 1967, being finally deactivated on May 5, 1968.

References

{{DEFAULTSORT:Essa-4 Spacecraft launched in 1967 Weather satellites of the United States Television Infrared Observation Satellites