COSMOS 1811 (also known as Kosmos-1811) is a reconnaissance satellite launched by the Soviet Union on January 9, 1987, from the Tyuratam Space Center's LC31 launch pad using a Soyuz-U launch vehicle. The spacecraft, based on the Yantar'-4K2 bus and equipped with two deployable solar arrays and batteries for power supply, has dimensions of 6.3 meters in length and 2.7 meters in diameter with a span of 6.3 meters. It weighs 2886 kg both at launch and dry mass. The mission involves reconnaissance using photo (film return type) with the payload Kobal't No. 852. Manufactured by TSSKB, its shape is cylindrical with two pans and it was launched for an unspecified owner (UNKS).