Kosmos 277

Kosmos 277 (Космос 277 meaning Cosmos 277), known before launch as DS-P1-Yu No.20, was a Soviet satellite which was used as a radar calibration target for tests of anti-ballistic missiles. It was a 325 kg spacecraft, which was built by the Yuzhnoye Design Bureau, and launched in 1969 as part of the Dnepropetrovsk Sputnik programme.

Launch
Kosmos 277 was launched from Site 133/1 at the Plesetsk Cosmodrome, atop a Kosmos-2I 63SM carrier rocket. The launch occurred on 4 April 1969 at 13:00:04 UTC, and resulted in Kosmos 277's successful deployment into low Earth orbit. Upon reaching orbit, it was assigned its Kosmos designation, and received the International Designator 1969-033A.

Kosmos 277 was operated in an orbit with a perigee of 256 km, an apogee of 412 km, 70.9 degrees of inclination, and an orbital period of 91.2 minutes. It remained in orbit until it decayed and reentered the atmosphere on 6 July 1969. It was the twentieth of seventy nine DS-P1-Yu satellites to be launched, and the nineteenth of seventy two to successfully reach orbit.