ATS-4 (Applications Technology Satellite) also known as ATS-D was a

communications satellite A communications satellite is an artificial satellite that relays and amplifies radio telecommunication signals via a Transponder (satellite communications), transponder; it creates a communication channel between a source transmitter and a Rad ...

launched by

NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...

on August 10, 1968 from

Cape Canaveral Cape Canaveral () is a cape (geography), cape in Brevard County, Florida, in the United States, near the center of the state's Atlantic Ocean, Atlantic coast. Officially Cape Kennedy from 1963 to 1973, it lies east of Merritt Island, separated ...

through an

Atlas-Centaur The Atlas-Centaur was a United States expendable launch vehicle derived from the SM-65 Atlas D missile. The vehicle featured a Centaur (rocket stage), Centaur upper stage, the first such stage to use high-performance liquid hydrogen as fuel. La ...

(AC-17) rocket.

Objectives

The objective of ATS-4 was to investigate the possibilities of a gravity gradient stabilization system (the method of stabilizing artificial satellites).

Features

The satellite has a cylindrical shape with a diameter and height (about considering the motor cover) with the surface covered by

solar panel A solar panel is a device that converts sunlight into electricity by using photovoltaic (PV) cells. PV cells are made of materials that produce excited electrons when exposed to light. These electrons flow through a circuit and produce direct ...

s that generated a maximum of 350 W of power, and stabilized by

gravity In physics, gravity (), also known as gravitation or a gravitational interaction, is a fundamental interaction, a mutual attraction between all massive particles. On Earth, gravity takes a slightly different meaning: the observed force b ...

gradient. It was based on the

Hughes Aircraft The Hughes Aircraft Company was a major American aerospace company, aerospace and defense contractor founded on February 14, 1934 by Howard Hughes in Glendale, California, as a division of the Hughes Tool Company. The company produced the Hughes ...

HS-306

bus A bus (contracted from omnibus, with variants multibus, motorbus, autobus, etc.) is a motor vehicle that carries significantly more passengers than an average car or van, but fewer than the average rail transport. It is most commonly used ...

Instruments

A total of four experiments were conducted during the mission: *

Microwave Microwave is a form of electromagnetic radiation with wavelengths shorter than other radio waves but longer than infrared waves. Its wavelength ranges from about one meter to one millimeter, corresponding to frequency, frequencies between 300&n ...

Transponder In telecommunications, a transponder is a device that, upon receiving a signal, emits a different signal in response. The term is a blend of ''transmitter'' and ''responder''. In air navigation or radio frequency identification, a flight trans ...

* Gravity Gradient Stabilization * Image Orthicon (Day/Night) Camera *

Ion Thruster An ion thruster, ion drive, or ion engine is a form of electric propulsion used for spacecraft propulsion. An ion thruster creates a cloud of positive ions from a neutral gas by ionizing it to extract some electrons from its atoms. The i ...

Mission

The Atlas and Centaur stages performed satisfactorily and placed the

Centaur A centaur ( ; ; ), occasionally hippocentaur, also called Ixionidae (), is a creature from Greek mythology with the upper body of a human and the lower body and legs of a horse that was said to live in the mountains of Thessaly. In one version o ...

/ATS-4 in an elliptical

parking Parking is the act of stopping and disengaging a vehicle and usually leaving it unoccupied. Parking on one or both sides of a road is often permitted, though sometimes with restrictions. Some buildings have parking facilities for use of the bu ...

orbit. However the Centaur stage failed to re-ignite after a 61-minute coast. The failure was determined to be freezing of the

hydrogen peroxide Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscosity, viscous than Properties of water, water. It is used as an oxidizer, bleaching agent, and antiseptic, usua ...

supply lines to the Centaur engines. High

atmospheric drag In fluid dynamics, drag, sometimes referred to as fluid resistance, is a force acting opposite to the direction of motion of any object moving with respect to a surrounding fluid. This can exist between two fluid layers, two solid surfaces, or b ...

due to the low altitude of the achieved orbit (186 km

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 ...

) precipitated the

orbital decay Orbital decay is a gradual decrease of the distance between two orbiting bodies at their closest approach (the periapsis) over many orbital periods. These orbiting bodies can be a planet and its satellite, a star and any object orbiting it, or ...

of the spacecraft. ATS-4 still achieved good results in some of the experiments, but the primary objective of achieving gravity gradient stabilization of a satellite was not reached. ATS-4 reentered the atmosphere on 17 October 1968.

References

External links

ATS, Past NASA Missions

ATS, NASA Science Missions
{{Orbital launches in 1968 1968 in spaceflight Applications Technology Satellites