| Kosmos 521 | |
| Mission Type: | ASAT target |
| Cospar Id: | 1972-074A |
| Spacecraft Type: | DS-P1-M |
| Manufacturer: | Yuzhnoye |
| Launch Date: | UTC |
| Launch Rocket: | Kosmos-3M |
| Launch Site: | Plesetsk 132/2 |
| Orbit Reference: | Geocentric |
| Orbit Regime: | Low Earth |
| Orbit Inclination: | 65.8 degrees |
| Orbit Period: | 104.9 minutes |
| Apsis: | gee |
Kosmos 521 (Russian: Космос 521 meaning Cosmos 521), also known as DS-P1-M No.4 is a satellite which was intended for use as a target for tests of anti-satellite weapons. It was launched by the Soviet Union in 1972 as part of the Dnepropetrovsk Sputnik programme,[1] and was to have been used as a target for an IS-A interceptor, as part of the Istrebitel Sputnikov programme. A malfunction aboard the satellite rendered it useless, and the interceptor was not launched.[2]
It was launched aboard a Kosmos-3M carrier rocket,[3] from Site 132/2 at the Plesetsk Cosmodrome. The launch occurred at 20:18:59 UTC on 29 September 1972.[4]
Kosmos 521 was placed into a low Earth orbit with a perigee of, an apogee of, 65.8 degrees of inclination, and an orbital period of 104.9 minutes.[1] No attempt to intercept the satellite was made after its onboard telemetry system malfunctioned. As of 2009, it is still in orbit.[2] [5] Western analysts did not identify Kosmos 521 as being associated with the Soviet ASAT programme until records were declassified.
Kosmos 521 was the last of the five original DS-P1-M satellites to be launched,[1] of which all but the first were successfully reached orbit. Despite its successful launch, the satellite malfunctioned shortly after reaching orbit, and was unusable. Subsequent launches used a modified version of the DS-P1-M, known as Lira.[6]