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]
Kosmos 521 was placed into a low Earth orbit with a perigee of 987 kilometres (613 mi), an apogee of 992 kilometres (616 mi), 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]
Payloads are separated by bullets ( · ), launches by pipes ( | ). Crewed flights are indicated in underline. Uncatalogued launch failures are listed in italics. Payloads deployed from other spacecraft are denoted in (brackets).
