Kosmos 954

Kosmos 954 (Космос 954) was a reconnaissance satellite launched by the Soviet Union in 1977. A malfunction prevented safe separation of its onboard nuclear reactor; when the satellite reentered the Earth's atmosphere the following year it scattered radioactive debris over northern Canada, prompting an extensive cleanup operation.

Launch and operation
The satellite was part of the Soviet Union's RORSAT programme, a series of reconnaissance satellites which observed ocean traffic, including surface vessels and nuclear submarines, using active radar. It was assigned the Kosmos number 954 and was launched on September 18, 1977 at 13:55 UTC from the Baikonur Cosmodrome, on a Tsyklon-2 carrier rocket. With an orbital inclination of 65°, a periapsis of 259 km and apoapsis of 277 km, it orbited the Earth every 89.5 minutes. Powered by a liquid sodium-potassium thermionic converter driven by a nuclear reactor containing around 50 kg of Uranium 235, the satellite was intended for long-term on-orbit observation, but by December 1977 the satellite had deviated from its designed orbit and its flightpath was becoming increasingly erratic. In mid-December North American Aerospace Defense Command, which had assigned the satellite the Satellite Catalog Number 10361, noticed Kosmos 954 making erratic manoeuvres, changing the altitude of its orbit by up to 50 miles, as its Soviet operators struggled to control their failing spacecraft. In secret meetings Soviet officials warned their US counterparts that they had lost control over the vehicle, and that the system which was intended to propel the spent reactor core into a safe disposal orbit had failed.

At 11:53 AM GMT on January 24, 1978 Kosmos 954 reentered the Earth's atmosphere while travelling on a northeastward track over western Canada. At first the USSR claimed that the satellite had been completely destroyed during re-entry, but later searches showed debris from the satellite had been deposited on Canadian territory along a 600 km path from Great Slave Lake to Baker Lake. The area spans portions of the Northwest Territories, present-day Nunavut, Alberta and Saskatchewan.

Recovery
The effort to recover radioactive material from the satellite was dubbed Operation Morning Light. Covering a total area of 124000 km2, the joint Canadian-American team swept the area by foot and air in Phase I from January 24, 1978 to April 20, 1978 and Phase II from April 21, 1978 to October 15, 1978. They were ultimately able to recover 12 larger pieces of the satellite. All but two fragments recovered were radioactive. These pieces displayed radioactivity of up to 1.1 sieverts per hour, yet they only comprised an estimated 1% of the fuel. "One fragment had the (lethal) radiation of 500 R/h, which is 100 times higher than the maximum annual [per-person] radiation level of 5 rem."

Aftermath
Under the terms of the 1972 Space Liability Convention, a state which launches an object into space is liable for damages caused by that object. For the recovery efforts, the Canadian government billed the Soviet Union $6,041,174.70 for actual expenses and additional compensation for future unpredicted expenses; the U.S.S.R. eventually paid the sum of C$3 million.

Kosmos 954 was not the first nuclear-powered RORSAT to fail; a launch of a similar satellite in 1973 failed, dropping its reactor into the Pacific Ocean north of Japan. Kosmos 1402 also failed, dropping its reactor into the South Atlantic in 1983. Subsequent RORSATs were equipped with a backup core ejection mechanism &mdash; when the primary failed on Kosmos 1900 in 1988 this system succeeded in raising the core to a safe disposal orbit.

A problem of a lesser scale occurred with the American nuclear-powered satellite: in November 1979 the SNAP-10A began shedding, eventually losing 50 pieces of traceable debris. Although the main body remains in place, radioactive material may have been released.