Basin. This map shows the location of Arctic research facilities during the mid-1970s and the tracks of drifting stations between 1958 and 1975. Another benefit from the Cold War was the acquisition of observations from United States and Soviet naval voyages into the Arctic. In 1958 an American nuclear submarine, the Nautilus was the first ship to reach the North Pole. In the decades that followed submarines regularly roamed under the Arctic sea ice, collecting sonar observations of the ice thickness and extent as they went. These data became available after the Cold War, and have provided evidence of thinning of the Arctic sea ice. The Soviet navy also operated in the Arctic, including a sailing of the nuclear-powered ice breaker Arktika to the North Pole in 1977, the first time a surface ship reached the pole. Scientific expeditions to the Arctic also became more common during the Cold-War decades, sometimes benefiting logistically or financially from the military interest. In 1966 the first deep ice core in Greenland was drilled at Camp Century, providing a glimpse of climate through the last ice age. This record was lengthened in the early 1990s when two deeper cores were taken from near the center of the Greenland Ice Sheet. Beginning in 1979 the Arctic Ocean Buoy Program (the International Arctic Buoy Program since 1991) has been collecting meteorological and ice-drift data across the Arctic Ocean with a network of 20 to 30 buoys. Satellite era The end of the Soviet Union in 1991 led to a dramatic decrease in regular observations from the Arctic. The Russian government ended the system of drifting North Pole stations, and closed many of the surface stations in the Russian Arctic. Likewise the United States and Canadian governments cut back on spending for Arctic observing as the perceived need for the DEWLINE declined. As a result, the most complete collection of surface observations from the Arctic is for the period 1960 to 1990. The extensive array of satellite-based remote-sensing instruments now in orbit has helped to replace some of the observations that were lost after the Cold War, and has provided coverage that was impossible without them. Routine satellite observations of the Arctic began in the early 1970s, expanding and improving ever since. A result of these observations is a thorough record of sea-ice extent in the Arctic since 1979; the decreasing extent seen in this record (NASA,