Gamma was a

Soviet The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, ...

gamma ray telescope. It was launched on 11 July 1990 into an orbit around

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's sur ...

with a height of 375 km and an

inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a reference plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Ea ...

of 51.6 degrees. It lasted for around 2 years. On board the mission were three telescopes, all of which could be pointed at the same source. The project was a joint Soviet-French project.

Background

The Gamma-1 telescope was the main telescope. It consisted of 2

scintillation counter A scintillation counter is an instrument for detecting and measuring ionizing radiation by using the excitation effect of incident radiation on a scintillating material, and detecting the resultant light pulses. It consists of a scintillator wh ...

s and a gas Cerenkov counter. With an effective area of around , it operated in the energy range of 50 MeV to 6 GeV. At 100 MeV it initially had an

angular resolution Angular resolution describes the ability of any image-forming device such as an optical or radio telescope, a microscope, a camera, or an eye, to distinguish small details of an object, thereby making it a major determinant of image resolut ...

of 1.5 degrees, with a

field of view The field of view (FoV) is the extent of the observable world that is seen at any given moment. In the case of optical instruments or sensors it is a solid angle through which a detector is sensitive to electromagnetic radiation. Human ...

of 5 degrees and an energy resolution of 12%. A Telezvezda

star tracker A star tracker is an optical device that measures the positions of stars using photocells or a camera. As the positions of many stars have been measured by astronomers to a high degree of accuracy, a star tracker on a satellite or spacecraft may ...

increased the pointing position accuracy of the Gamma-1 telescope to 2

arcminute A minute of arc, arcminute (arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of one degree. Since one degree is of a turn (or complete rotation), one minute of arc is of a turn. The n ...

s by tracking stars up to an

apparent magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's ...

of 5 within its 6 by 6 degree field of view. However, due to the failure of power to a

spark chamber {{short description, Charged particle detector A spark chamber is a particle detector: a device used in particle physics for detecting electrically charged particles. They were most widely used as research tools from the 1930s to the 1960s and hav ...

, for most of the mission the resolution was around 10 degrees. The telescope was conceived in 1965, as part of the Soviet Cloud Space Station, which evolved into the Multi-module Orbital Complex (MOK). When work on Gamma finally began in 1972, it was intended to create a ''Gamma observatory'', the first space station module for MOK, the first modular space station in the

Salyut programme The ''Salyut'' programme (russian: Салют, , meaning "salute" or "fireworks") was the first space station programme, undertaken by the Soviet Union. It involved a series of four crewed scientific research space stations and two crewed m ...

. For this, it was designed to add the scientific instruments of the observatory to a spacecraft derived from the

Progress spacecraft The Progress (russian: Прогресс) is a Russian expendable cargo spacecraft. Its purpose is to deliver the supplies needed to sustain a human presence in orbit. While it does not carry a crew, it can be boarded by astronauts when docked t ...

– with the Progress in turn being a

Soyuz spacecraft Soyuz () is a series of spacecraft which has been in service since the 1960s, having made more than 140 flights. It was designed for the Soviet space program by the Korolev Design Bureau (now Energia). The Soyuz succeeded the Voskhod spacecr ...

derivate – and that this spacecraft would dock to a MOK space station. However, in 1974, at the time it became a joint venture with France, the MOK space station project was canceled, and in February 1976, the Soviet space program was reconfigured. When on 16 February 1979 production of the telescope was authorized, the plans for the Soviet space station modules had evolved to use the Functional Cargo Block of the

TKS spacecraft The TKS spacecraft (russian: Транспортный корабль снабжения, , ''Transport Supply Spacecraft'', GRAU index 11F72) was a Soviet spacecraft conceived in the late 1960s for resupply flights to the military Almaz space ...

instead, with the Kvant-1 Roentgen observatory eventually becoming the first such module for

Mir ''Mir'' (russian: Мир, ; ) was a space station that operated in low Earth orbit from 1986 to 2001, operated by the Soviet Union and later by Russia. ''Mir'' was the first modular space station and was assembled in orbit from 1986 to&n ...

– as a result of these changes the ''Gamma observatory'' was redesigned as the free flying ''Gamma satellite''. At that time the telescope was authorized in 1979, it was planned to be launched in 1984, but the actual launch was delayed until 1990.

Operation

The Disk-M telescope operated in the energy range 20 keV - 5 MeV. It consisted of

Sodium iodide Sodium iodide (chemical formula NaI) is an ionic compound formed from the chemical reaction of sodium metal and iodine. Under standard conditions, it is a white, water-soluble solid comprising a 1:1 mix of sodium cations (Na+) and iodide anions (I ...

scintillation

crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macro ...

s, and had an angular resolution of 25 arcminutes. However, it stopped working shortly after the mission was launched. Finally, the Pulsar X-2 telescope had 30 arcminute resolution and a 10 deg x 10 deg field of view, and operated in the energy range 2-25 keV. Observations included studies of the

Vela Pulsar The Vela Pulsar (PSR J0835-4510 or PSR B0833-45) is a radio, optical, X-ray- and gamma-emitting pulsar associated with the Vela Supernova Remnant in the constellation of Vela. Its parent Type II supernova exploded approximately 11,000� ...

, the

Galactic Center The Galactic Center or Galactic Centre is the rotational center, the barycenter, of the Milky Way galaxy. Its central massive object is a supermassive black hole of about 4 million solar masses, which is called Sagittarius A*, a compact ra ...

Cygnus X-1 Cygnus X-1 (abbreviated Cyg X-1) is a galactic X-ray source in the constellation Cygnus and was the first such source widely accepted to be a black hole. It was discovered in 1964 during a rocket flight and is one of the ...

Hercules X-1 Hercules X-1 (Her X-1), also known as 4U1656+35, is a moderately strong X-ray binary source first studied by the Uhuru satellite. It is composed of a neutron star accreting matter from a normal star (HZ Her) probably due to Roche lobe overflow. ...

and the

Crab Nebula The Crab Nebula (catalogue designations M1, NGC 1952, Taurus A) is a supernova remnant and pulsar wind nebula in the constellation of Taurus. The common name comes from William Parsons, 3rd Earl of Rosse, who observed the object in 1842 u ...

. The telescopes also measured the Sun during peak solar activity.

References

External links

Gamma on the Internet Encyclopedia of Science

{{Orbital launches in 1990 Gamma-ray telescopes Space telescopes Spacecraft launched in 1990 Soviet space observatories France–Soviet Union relations