Kosmos 261 (russian: Космос 261 meaning ''Cosmos 261''), also known as DS-U2-GK No.1, was a

Soviet The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, it was nominally a federal union of fifteen nation ...

satellite A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioi ...

which was launched in 1968 as part of the

Dnepropetrovsk Sputnik Dnepropetrovsk Sputnik (russian: Днепропетровский Спутник; ua, Дніпропетровський супутник), also known as DS, was a series of satellites launched by the Soviet Union between 1961 and 1982. DS satel ...

programme. It was a spacecraft, which was built by the

Yuzhnoye Design Bureau Pivdenne Design Office ( uk, Державне конструкторське бюро «Південне» ім. М. К. Янгеля , lit=State design bureau "Southern", named after M. K. Yangel, translit=Derzhavne konstruktors ...

, 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. Air density, like air pressure, decreases with increasing altitude. It also changes with variation in atmospheric pressure, temperature a ...

in the upper atmosphere, and investigate aurorae. Kosmos 261 set the way for the

Intercosmos Interkosmos (russian: Интеркосмос) was a Soviet space program, designed to help the Soviet Union's allies with crewed and uncrewed space missions. The program was formed in April 1967 in Moscow. All members of the program from USSR ...

Program.

Hungary Hungary ( hu, Magyarország ) is a landlocked country in Central Europe. Spanning of the Pannonian Basin, Carpathian Basin, it is bordered by Slovakia to the north, Ukraine to the northeast, Romania to the east and southeast, Serbia to the ...

Poland Poland, officially the Republic of Poland, is a country in Central Europe. It is divided into 16 administrative provinces called voivodeships, covering an area of . Poland has a population of over 38 million and is the fifth-most populou ...

Romania Romania ( ; ro, România ) is a country located at the crossroads of Central, Eastern, and Southeastern Europe. It borders Bulgaria to the south, Ukraine to the north, Hungary to the west, Serbia to the southwest, Moldova to the east, and ...

Czechoslovakia , rue, Чеськословеньско, , yi, טשעכאסלאוואקיי, , common_name = Czechoslovakia , life_span = 1918–19391945–1992 , p1 = Austria-Hungary , image_p1 ...

DDR DDR or ddr may refer to: *ddr, ISO 639-3 code for the Dhudhuroa language *DDr., title for a double doctorate in Germany *DDR, station code for Dadar railway station, Mumbai, India *' (German Democratic Republic), official name of the former East ...

and

Bulgaria Bulgaria (; bg, България, Bǎlgariya), officially the Republic of Bulgaria,, ) is a country in Southeast Europe. It is situated on the eastern flank of the Balkans, and is bordered by Romania to the north, Serbia and North Macedo ...

were the six Soviet Bloc countries that collaborated in the experiments on board the satellite. A

Kosmos-2I Kosmos-2I ( GRAU Index: 11K63, also known as Cosmos-2I and also known by the designation Kosmos-2) is the designation applied to two Soviet carrier rockets, members of the R-12 Kosmos rocket family, which were used to orbit satellites between 19 ...

63SM

carrier rocket A launch vehicle or carrier rocket is a rocket designed to carry a payload (spacecraft or satellites) from the Earth's surface to outer space. Most launch vehicles operate from a launch pads, supported by a launch control center and syste ...

was used to launch Kosmos 261 into

low Earth orbit A low Earth orbit (LEO) is an orbit around Earth with a period of 128 minutes or less (making at least 11.25 orbits per day) and an eccentricity less than 0.25. Most of the artificial objects in outer space are in LEO, with an altitude never mor ...

from Site 133/1 at the

Plesetsk Cosmodrome Plesetsk Cosmodrome ( rus, Космодром «Плесецк», r=Kosmodrom "Plesetsk", p=kəsmɐˈdrom plʲɪˈsʲet͡sk) is a Russian spaceport located in Mirny, Arkhangelsk Oblast, about 800 km north of Moscow and approximately 200 ...

. 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 The International Designator, also known as COSPAR ID, is an international identifier assigned to artificial objects in space. It consists of the launch year, a three-digit incrementing launch number of that year and up to a three-letter code repr ...

1968-117A. The

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

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. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any ell ...

of , an

apogee An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any ell ...

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