Kosmos-1669 (Russian: Космос-1669 meaning Cosmos 1669) was a Progress spacecraft used to resupply the Salyut 7 space station. It was a Progress 7K-TG spacecraft with the serial number 126.

Kosmos-1669 was launched by a Soyuz-U carrier rocket from Site 1/5 at the Baikonur Cosmodrome, at 13:05 UTC on 19 July 1985. The spacecraft docked with the aft port of Salyut 7 at 15:05 UTC on 21 July. Following undocking on 28 August, it moved away from the station, before returning and redocking to test the reliability of the docking system.[1] It undocked for a second time at 21:50 UTC,[2] and was deorbited on 30 August, with the spacecraft burning up over the Pacific Ocean at 01:20 UTC.

Kosmos-1669 was the first cargo spacecraft to visit Salyut 7 after its reactivation, and also the last Progress flight as part of the Salyut programme. It delivered new spacesuits, to replace ones damaged by cold temperatures whilst Salyut 7 was deactivated,[3] as well as replacement parts and consumables. This Progress mission was followed by one last cargo mission to Salyut 7, but carried out by an TKS spacecraft: TKS-4, which would become the fourth and last flight of an TKS craft. The next following mission of a Progress cargo craft, Progress 25, flew to Mir.[1]

As of 2009, Kosmos-1669 is the only Progress spacecraft to have received a Kosmos designation, which are usually reserved for military, experimental and failed spacecraft. It has been reported that this may have been an error due to confusion with a TKS spacecraft which later became Kosmos 1686,[4] or that the spacecraft may have gone out of control shortly after launch, but then been recovered after the Kosmos designation had been applied.[1] Alternatively, it could have been given the designation as it was used to test modifications that would be used on future Progress missions.[3] Some news agencies reported that it was a free-flying Progress-derived spacecraft,[3] or that it was a new type of spacecraft derived from the Progress.[5]

See also