In the 1930s, gold was discovered on the North Arm of Great Slave Lake, leading to the establishment of Yellowknife which would become the capital of the NWT. In 1960, an all-season highway was built around the west side of the lake, originally an extension of the Mackenzie Highway but now known as Yellowknife Highway or Highway 3. On January 24, 1978, a Soviet Radar Ocean Reconnaissance Satellite, named Kosmos 954, built with an onboard nuclear reactor fell from orbit and disintegrated. Pieces of the nuclear core fell in the vicinity of Great Slave Lake. Almost all of the nuclear debris was recovered by a joint Canadian Armed Forces and United States Armed Forces military operation called Operation Morning Light.