Kosmos 261 (, ), also known as DS-U2-GK No.1, was a Soviet

satellite A satellite or an artificial satellite is an object, typically a spacecraft, placed into orbit around a celestial body. They have a variety of uses, including communication relay, weather forecasting, navigation ( GPS), broadcasting, scient ...

which was launched in 1968 as part of the

Dnepropetrovsk Sputnik Dnepropetrovsk Sputnik (; ), also known as DS, was a series of satellites launched by the Soviet Union between 1961 and 1982. DS satellites were used for a number of missions, including technological and scientific research, and radar tracking t ...

programme. It was a spacecraft, which was built by the Yuzhnoye Design Bureau, and was used to study the

density of air The density of air or atmospheric density, denoted '' ρ'', is the mass per unit volume of Earth's atmosphere at a given point and time. Air density, like air pressure, decreases with increasing altitude. It also changes with variations in atmosph ...

in the upper atmosphere, and investigate aurorae. Kosmos 261 set the way for the Intercosmos Program. Hungary, Poland, Romania, Czechoslovakia, DDR and Bulgaria were the six

Soviet Bloc The Eastern Bloc, also known as the Communist Bloc (Combloc), the Socialist Bloc, the Workers Bloc, and the Soviet Bloc, was an unofficial coalition of communist states of Central and Eastern Europe, Asia, Africa, and Latin America that were a ...

countries that collaborated in the experiments on board the satellite. A

Kosmos-2I The Kosmos (also spelled Cosmos, Russian: ) rockets were a series of Soviet and subsequently Russian rockets, derived from the R-12 and R-14 missiles, the best known of which is the Kosmos-3M, which has made over 440 launches. The Kosmos fami ...

63SM

carrier rocket A launch vehicle is typically a rocket-powered vehicle designed to carry a payload (a crewed spacecraft or satellites) from Earth's surface or lower atmosphere to outer space. The most common form is the ballistic missile-shaped multistag ...

was used to launch Kosmos 261 into

low Earth orbit A low Earth orbit (LEO) is an geocentric orbit, orbit around Earth with a orbital period, period of 128 minutes or less (making at least 11.25 orbits per day) and an orbital eccentricity, eccentricity less than 0.25. Most of the artificial object ...

from Site 133/1 at the

Plesetsk Cosmodrome Plesetsk Cosmodrome () is a Russian spaceport located in Mirny, Arkhangelsk Oblast, near the town of Plesetsk, from which it takes its name. Until 2025 and the commissioning of the Andøya Space, Andøya base in Norway, it was the only operati ...

. The launch occurred at 23:55:00 UTC on 19 December 1968, and resulted in the successful insertion of the satellite into orbit. Upon reaching orbit, the satellite was assigned its Kosmos designation, and received the International Designator 1968-117A. The

North American Aerospace Defense Command North American Aerospace Defense Command (NORAD ; , CDAAN), known until March 1981 as the North American Air Defense Command, is a Combined operations, combined organization of the United States and Canada that provides aerospace warning, air ...

assigned it the catalogue number 03624. Kosmos 261 was the first of two DS-U2-GK satellites to be launched. It was operated in an orbit with a

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 ...

of , an

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 ...

of , 71 degrees of

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 Eart ...

, and an

orbital period The orbital period (also revolution period) is the amount of time a given astronomical object takes to complete one orbit around another object. In astronomy, it usually applies to planets or asteroids orbiting the Sun, moons orbiting planets ...

of 92.68 minutes. It decayed from orbit and reentered the atmosphere on 12 February 1969.

References

Spacecraft launched in 1968 Kosmos satellites Dnepropetrovsk Sputnik program {{USSR-spacecraft-stub

See also

References