Nuclear weapons tests in Australia known at the time as Christmas Island (not to be confused with Christmas Island in the Indian Ocean) between 1957 and 1958. These were airbursts mostly occurring over water or suspended a few hundred metres above the ground by balloon. In Australia there were three sites. Testing was carried out between 1952 and 1957 and was mostly done at the surface. A few hundred smaller scale tests were conducted at both Emu Field and Maralinga between 1953 and 1963. Two separate atomic test projects occurred at the islands, the first being Operation Hurricane and the second being Operation Mosaic The
History of the Teller–Ulam design "secret"), the United States agreed to exchange some of its nuclear designs with Great Britain, leading to the 1958 US-UK Mutual Defence Agreement. The People's Republic of China detonated its first device using a Teller–Ulam design June 1967 ("Test No. 6"), a mere 32 months after detonating its first fission weapon (the shortest fission-to-fusion development yet known), with a yield of 3.3 Mt. Little is known about the Chinese thermonuclear program, however. Very little is known about the French development of the Teller–Ulam design beyond the fact that they detonated a 2.6 Mt device in the "Canopus" test in August