| Major contractors | Yuzhnoye |
|---|---|
| Bus | DS-U2-GK |
| Mission type | Aeronomy Auroral |
| Launch date | 19 December 1968 23:55:00 GMT |
| Carrier rocket | Kosmos-2I 63SM |
| Launch site | Plesetsk Site 133/1 |
| Orbital decay | 12 February 1969 |
| COSPAR ID | 1968-117A |
| Mass | 347 kilograms (770 lb)[1] |
| Orbital elements | |
| Regime | Low Earth |
| Inclination | 71° |
| Apoapsis | 611 kilometres (380 mi) |
| Periapsis | 201 kilometres (125 mi) |
| Orbital period | 92.68 minutes |
Kosmos 261 (Russian: Космос 261 meaning Cosmos 261), also known as DS-U2-GK #1, was a Soviet satellite which was launched in 1968 as part of the Dnepropetrovsk Sputnik programme. It was a 347-kilogram (770 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.[1]
A Kosmos-2I 63SM carrier rocket was used to launch Kosmos 261 into low Earth orbit from Site 133/1 at the Plesetsk Cosmodrome.[2] The launch occurred at 23:55:00 GMT on 19 December 1968, and resulted in the successful insertion of the satellite into orbit.[3] Upon reaching orbit, the satellite was assigned its Kosmos designation, and received the International Designator 1968-117A.[4] The North American Aerospace Defense Command assigned it the catalogue number 03624.
Kosmos 261 was the first of two DS-U2-GK satellites to be launched.[1][5] It was operated in an orbit with a perigee of 201 kilometres (125 mi), an apogee of 611 kilometres (380 mi), 71 degrees of inclination, and an orbital period of 92.68 minutes.[6] It decayed from orbit and reentered the atmosphere on 12 February 1969.[6]