Most of those nuclear tests were carried out in the atmosphere. Some tests were positioned for firing by airdrop, but metal towers were used for many Nevada tests at heights ranging from 100 to 700 feet (30-200 meters) above the ground surface.
In 1957 and 1958, helium-filled balloons, tethered to precise heights and locations 340 to 1,500 feet (105 to 500 meters) above ground, provided a simpler, quicker, and less expensive method for the testing of many experimental devices.
The tests of the atmospheric era took place in Yucca and Frenchman Flats. The 119 nuclear tests that were conducted at the NTS during the atmospheric testing era (1951-1958) consist of 97 nuclear tests conducted in the atmosphere, of two cratering tests, detonated at depths less than 100 feet (30 meters), and of 20 underground tests.
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The Area 12 Camp, located at the extreme Northwest end of the Nevada Test Site, supports miners from the tunnels in Ranier Mesa with overnight accomodations for 600 people.
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Aerial view of the recording trailer park and the cables connected to the test site
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Little more than a minute after a mid-1969 underground nuclear detonation, the ten-story tall 200-ton instrument tower was pulled along tracks by cables from above the detonation point. About 20 minutes later, the ground collapsed into the cavity caused by the detonation, producing a 175-foot crater
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Underground Nuclear Test
The HURON KING underground nuclear test was a DOD sponsored event on 24 June 1980. The test involved a device with a yield of less than 20 kilotons, and tested the effects of system generated electromagnetic pulse [SGEMP] on a full-scale operating DSCS-3 military communications satellite. The spacecraft was contained in a large above-ground tank.
http://www.globalsecurity.org/wmd/facility/nts.htm