The Orbiting Astronomical Observatory 2 (OAO-2, nicknamed ''Stargazer'') was the first successful

space telescope A space telescope (also known as space observatory) is a telescope in outer space used to observe astronomical objects. Suggested by Lyman Spitzer in 1946, the first operational telescopes were the American Orbiting Astronomical Observatory, OAO ...

(first space telescope being OAO-1, which failed to operate once in orbit), launched on December 7, 1968. 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 ...

rocket launched it into a nearly circular altitude Earth orbit. Data was collected in ultraviolet on many sources including comets, planets, and galaxies. It had two major instrument sets facing in opposite directions; the Smithsonian Astrophysical Observatory (SAO) and the Wisconsin Experiment Package (WEP).Orbiting Astronomical Observatory OAO-2
/ref> One discovery was large halos of hydrogen gas around comets, and it also observed Nova Serpentis, which was a nova discovered in 1970.

Celescope: Smithsonian Astrophysical Observatory

The Smithsonian Astrophysical Observatory, also called Celescope, had four 12 inch (30.5 cm) Schwarzschild telescopes that fed into Uvicons.High-Resolution Telescopes
/ref> The Uvicon was an ultra-violet light detector based on the Westinghouse

Vidicon Video camera tubes are devices based on the cathode-ray tube that were used in television cameras to capture television images, prior to the introduction of charge-coupled device (CCD) image sensors in the 1980s. Several different types of tubes ...

. Ultraviolet light was converted into

electron The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary charge, elementary electric charge. It is a fundamental particle that comprises the ordinary matter that makes up the universe, along with up qua ...

s which were in turn converted to a voltage as those electrons hit the detection area of the tube. There has been a Uvicon in the collection of the

Smithsonian Institution The Smithsonian Institution ( ), or simply the Smithsonian, is a group of museums, Education center, education and Research institute, research centers, created by the Federal government of the United States, U.S. government "for the increase a ...

since 1973. Various filters,

photocathode A photocathode is a surface engineered to convert light (photons) into electrons using the photoelectric effect. Photocathodes are important in accelerator physics where they are utilised in a photoinjector to generate high brightness electron ...

s, and electronics aided in collecting data in several

ultraviolet light Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of th ...

passband A passband is the range of frequency, frequencies or wavelengths that can pass through a Filter (signal processing), filter. For example, a radio receiver contains a bandpass filter to select the frequency of the desired radio signal out of all t ...

s. The detectors showed a gradual loss of sensitivity and the experiment was turned off in April 1970. By the time it finished about 10 percent of the sky was observed resulting in a catalog of 5,068 UV stars.

Wisconsin Experiment Package

The Wisconsin Experiment Package had seven different telescopes for ultraviolet observations.Wisconsin Experiment Package
/ref> For example, there was a nebular photoelectric photometer fed by a 16-inch (40.64 cm) telescope with a six-position filter wheel that unfortunately failed a few weeks after launch. Construction was supervised by Arthur Code of the

University of Wisconsin-Madison A university () is an institution of tertiary education and research which awards academic degrees in several academic disciplines. ''University'' is derived from the Latin phrase , which roughly means "community of teachers and scholars". Uni ...

. WEP observed over 1200 targets in ultraviolet light before the mission ended in early 1973.

Discoveries

In addition to the Celescope's catalog of UV stars, the WEP observed

comet A comet is an icy, small Solar System body that warms and begins to release gases when passing close to the Sun, a process called outgassing. This produces an extended, gravitationally unbound atmosphere or Coma (cometary), coma surrounding ...

Tago-Sato-Kosaka and found it to be surrounded by a cloud of hydrogen, confirming that the comet was largely made up of water, and detected the 2175-angstrom bump, an increase in UV absorption at that wavelength that is still not fully explained.

Spacecraft bus

The observatory was built in the shape of an octagonal prism. It measured about and weighed .

References

External links