It was a 347-kilogram (765 lb) spacecraft,[1] which was built by the Yuzhnoye Design Bureau, and was used to study the density of air in the upper atmosphere, and investigate aurorae.

Hungary, Poland, Romania, Czechoslovakia, DDR and Bulgaria were the six Soviet Bloc countries that collaborated in the experiments on board the satellite.

[2] A Kosmos-2I 63SM carrier rocket was used to launch Kosmos 261 into low Earth orbit from Site 133/1 at the Plesetsk Cosmodrome.

[3] The launch occurred at 23:55:00 UTC on 19 December 1968, and resulted in the successful insertion of the satellite into orbit.

[5] The North American Aerospace Defense Command assigned it the catalogue number 03624.