Orbiting Astronomical Observatory
Encyclopedia
Satellite
In the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavour. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....
s were a series of four American space observatories
Space observatory
A space observatory is any instrument in outer space which is used for observation of distant planets, galaxies, and other outer space objects...
launched by NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
between 1966 and 1972, which provided the first high-quality observations of many objects in ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
light. Although two OAO missions were failures, the success of the other two increased awareness within the astronomical community of the benefits of space-based observations, and led to the instigation of the Hubble Space Telescope
Hubble Space Telescope
The Hubble Space Telescope is a space telescope that was carried into orbit by a Space Shuttle in 1990 and remains in operation. A 2.4 meter aperture telescope in low Earth orbit, Hubble's four main instruments observe in the near ultraviolet, visible, and near infrared...
.
OAO-1
The first OAO was launched successfully on 8 April 1966, carrying instruments to detect ultravioletUltraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
, X-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
and gamma ray
Gamma ray
Gamma radiation, also known as gamma rays or hyphenated as gamma-rays and denoted as γ, is electromagnetic radiation of high frequency . Gamma rays are usually naturally produced on Earth by decay of high energy states in atomic nuclei...
emission. Before the instruments could be activated, however, a power failure resulted in the termination of the mission after three days.
OAO-2
OAO-2 was launched on 7 December 1968, and carried 11 ultraviolet telescopeTelescope
A telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation . The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s , using glass lenses...
s. It observed successfully until January 1973, and contributed to many significant astronomical discoveries. Among these were the discovery that comet
Comet
A comet is an icy small Solar System body that, when close enough to the Sun, displays a visible coma and sometimes also a tail. These phenomena are both due to the effects of solar radiation and the solar wind upon the nucleus of the comet...
s are surrounded by enormous haloes of hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
, several hundred thousand kilometres across, and observations of nova
Nova
A nova is a cataclysmic nuclear explosion in a star caused by the accretion of hydrogen on to the surface of a white dwarf star, which ignites and starts nuclear fusion in a runaway manner...
e which found that their UV brightness often increased during the decline in their optical brightness.
OAO-B
OAO-B carried a 38-inch UV telescope, and should have provided spectra of fainter objects than had previously been observable. The booster rocket failed to separate from the satellite following its launch on 3 November 1970, and the satellite burned up as it re-entered the Earth's atmosphereEarth's atmosphere
The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...
.
OAO-3 (Copernicus)
OAO-3 was launched on 21 August 1972, and proved to be the most successful of the OAO missions. It was a collaborative effort between NASA and the UKUnited Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
's Science and Engineering Research Council, and carried an X-ray detector built by University College London
University College London
University College London is a public research university located in London, United Kingdom and the oldest and largest constituent college of the federal University of London...
's Mullard Space Science Laboratory in addition to an 80 cm UV telescope built by Princeton University
Princeton University
Princeton University is a private research university located in Princeton, New Jersey, United States. The school is one of the eight universities of the Ivy League, and is one of the nine Colonial Colleges founded before the American Revolution....
. After its launch, it was named Copernicus to mark the 500th anniversary of the birth of Nicolaus Copernicus
Nicolaus Copernicus
Nicolaus Copernicus was a Renaissance astronomer and the first person to formulate a comprehensive heliocentric cosmology which displaced the Earth from the center of the universe....
.
Copernicus operated until February 1981, and returned high resolution spectra of hundreds of stars along with extensive X-ray observations. Among the significant discoveries made by Copernicus were the discovery of several long-period pulsar
Pulsar
A pulsar is a highly magnetized, rotating neutron star that emits a beam of electromagnetic radiation. The radiation can only be observed when the beam of emission is pointing towards the Earth. This is called the lighthouse effect and gives rise to the pulsed nature that gives pulsars their name...
s, with rotation times of many minutes instead of the more typical second
Second
The second is a unit of measurement of time, and is the International System of Units base unit of time. It may be measured using a clock....
or less.
Launches
- OAO-1: Atlas-Agena DAtlas-AgenaThe Atlas-Agena was an American expendable launch system derived from the SM-65 Atlas missile. It was a member of the Atlas family of rockets, and was used for 119 orbital launches between 1960 and 1978....
from Launch Complex 12, Cape CanaveralCape Canaveral Air Force StationCape Canaveral Air Force Station is an installation of the United States Air Force Space Command's 45th Space Wing, headquartered at nearby Patrick Air Force Base. Located on Cape Canaveral in the state of Florida, CCAFS is the primary launch head of America's Eastern Range with four launch pads...
, Florida - OAO-2, OAO-B and OAO-3: Atlas-CentaurAtlas-CentaurThe Atlas-Centaur was an American expendable launch system designed and built by General Dynamics Convair Division in San Diego, CA. It was derived from the SM-65 Atlas missile. It was a member of the Atlas family of rockets, and was used for 61 orbital launches between 1962 and 1983. It was...
from Launch Complex 36, Cape Canaveral, Florida