ESSA 6 (or TOS-D) 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).

Details

ESSA 6 had a mass of at the time of launch. The satellite's electrical power was supplied by about 10,000 1x2 cm

solar cell A solar cell, also known as a photovoltaic cell (PV cell), is an electronic device that converts the energy of light directly into electricity by means of the photovoltaic effect.

s on the cover and 21 nickel-cadmium batteries. Two redundant wide-angle APT (Automatic Picture Transmission) cameras, mounted on opposite sides and perpendicular to the spin axis, captured images. This subsystem was a camera-transmitter setup, designed to transmit real-time daylight images of cloud cover to ground stations. It included two 2.54-cm vidicon cameras with lenses, mounted 180° apart. Each orbit, the cameras captured four or eight images, with picture taking lasting 8 seconds and transmission 200 seconds. The 800-line images were transmitted at 137.5 MHz to local APT stations, with reticle marks on the images to assist with geographical alignment. Each picture covered a 3100 x 3100 km area with 4 km resolution at

nadir The nadir is the direction pointing directly ''below'' a particular location; that is, it is one of two vertical directions at a specified location, orthogonal to a horizontal flat surface. The direction opposite of the nadir is the zenith. Et ...

, with a 30% overlap to ensure complete coverage. The base featured crossed-

dipole antenna In radio and telecommunications a dipole antenna or doublet is one of the two simplest and most widely used antenna types, types of antenna; the other is the monopole antenna, monopole. The dipole is any one of a class of antennas producin ...

s for command reception, while a

monopole antenna A monopole antenna is a class of radio antenna consisting of a straight rod-shaped conductor, often mounted perpendicularly over some type of conductive surface, called a ground plane. The current from the transmitter is applied, or for rece ...

provided telemetry (136.500 MHz) and tracking (136.770 MHz) from the top.

Spin rate Revolutions per minute (abbreviated rpm, RPM, rev/min, r/min, or r⋅min−1) is a unit of rotational speed (or rotational frequency) for rotating machines. One revolution per minute is equivalent to hertz. Standards ISO 80000-3:2019 defin ...

was regulated to 10.9 rpm using a Magnetic Attitude Spin Coil (MASC), which interacted with

Earth's magnetic field Earth's magnetic field, also known as the geomagnetic field, is the magnetic field that extends from structure of Earth, Earth's interior out into space, where it interacts with the solar wind, a stream of charged particles emanating from ...

to maintain a stable spin axis normal to the orbital plane, within ±1 degree.

Mission

ESSA 6 was launched on November 10, 1967, at 18:00

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 ...

, 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 Air Force Base Vandenberg may refer to: * Vandenberg (surname), including a list of people with the name * USNS ''General Hoyt S. Vandenberg'' (T-AGM-10), transport ship in the United States Navy, sank as an artificial reef in Key West, Florida * Vandenberg S ...

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

, USA. ESSA 6 had an inclination of 102.12°, and orbited the Earth once every 114.8 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 performed normally after launch. The APT camera system was successful, operating nearly continuously until November 4, 1969 when the spacecraft was deactivated.

References

Spacecraft launched in 1967 Weather satellites of the United States Television Infrared Observation Satellites {{Satellite-stub