Operation Mosaic

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Montebello Islands
Near Barrow Island in Australia
Map showing nuclear test sites in Australia
Coordinates 20°19′08″S 115°35′14″E / 20.31889°S 115.58722°E / -20.31889; 115.58722 (Montebello Test Site)
Type Nuclear test range
Site information
Operator United Kingdom
Status Inactive
Site history
In use 1953–1956
Country United Kingdom
Test site Montebello Islands, West Australia
Period 1956
Number of tests 2
Test type tower
Max. yield 60 kilotonnes of TNT (250 TJ)
Test series chronology

The United Kingdom's Mosaic nuclear test series was a group of 2 nuclear tests conducted in 1956. These tests followed the Operation Totem series and preceded the Operation Buffalo series.

At the time of the Royal Commission Into British Nuclear Testing in Australia (1984–85) there emerged a claim that the second 'Mosaic' test on 19 June 1956 was of a significantly higher explosive yield than suggested by available figures: 98kt as compared to 60. But this claim does not appear to stand up to investigation.[1]

United Kingdom's Mosaic series tests and detonations
Name [note 1] Date time (UT) Local time zone [note 2][2] Location [note 3] Elevation + height [note 4] Delivery, [note 5]
Purpose [note 6]
Device [note 7] Yield [note 8] Fallout [note 9] References Notes
G1 16 May 1956 03:50:?? aWST (8 hrs)
Montebello Islands, West Australia 20°22′55″S 115°32′53″E / 20.38207°S 115.54796°E / -20.38207; 115.54796 (G1) 4 m (13 ft) + 31 m (102 ft) tower,
weapons development
15 kt [3][4][5] Included deuterium; an apparent failure.
G2 19 June 1956 02:14:?? aWST (8 hrs)
Montebello Islands, West Australia 20°24′22″S 115°32′08″E / 20.40604°S 115.53555°E / -20.40604; 115.53555 (G2) 8 m (26 ft) + 31 m (102 ft) tower,
60 kt [3][4][5] Unexpectedly high yield, a sloika design with U238 tamper and fast neutrons, against with deuterium.
  1. ^ The US, France and Great Britain have code-named their test events, while the USSR and China did not, and therefore have only test numbers (with some exceptions – Soviet peaceful explosions were named). Word translations into English in parentheses unless the name is a proper noun. A dash followed by a number indicates a member of a salvo event. The US also sometimes named the individual explosions in such a salvo test, which results in "name1 – 1(with name2)". If test is canceled or aborted, then the row data like date and location discloses the intended plans, where known.
  2. ^ To convert the UT time into standard local, add the number of hours in parentheses to the UT time; for local daylight saving time, add one additional hour. If the result is earlier than 00:00, add 24 hours and subtract 1 from the day; if it is 24:00 or later, subtract 24 hours and add 1 to the day. All historical timezone data are derived from here:
  3. ^ Rough place name and a latitude/longitude reference; for rocket-carried tests, the launch location is specified before the detonation location, if known. Some locations are extremely accurate; others (like airdrops and space blasts) may be quite inaccurate. "~" indicates a likely pro-forma rough location, shared with other tests in that same area.
  4. ^ Elevation is the ground level at the point directly below the explosion relative to sea level; height is the additional distance added or subtracted by tower, balloon, shaft, tunnel, air drop or other contrivance. For rocket bursts the ground level is "N/A". In some cases it is not clear if the height is absolute or relative to ground, for example, Plumbbob/John. No number or units indicates the value is unknown, while "0" means zero. Sorting on this column is by elevation and height added together.
  5. ^ Atmospheric, airdrop, balloon, gun, cruise missile, rocket, surface, tower, and barge are all disallowed by the Partial Nuclear Test Ban Treaty. Sealed shaft and tunnel are underground, and remained useful under the PTBT. Intentional cratering tests are borderline; they occurred under the treaty, were sometimes protested, and generally overlooked if the test was declared to be a peaceful use.
  6. ^ Include weapons development, weapon effects, safety test, transport safety test, war, science, joint verification and industrial/peaceful, which may be further broken down.
  7. ^ Designations for test items where known, "?" indicates some uncertainty about the preceding value, nicknames for particular devices in quotes. This category of information is often not officially disclosed.
  8. ^ Estimated energy yield in tons, kilotons, and megatons. A ton of TNT equivalent is defined as 4.184 gigajoules (1 gigacalorie).
  9. ^ Radioactive emission to the atmosphere aside from prompt neutrons, where known. The measured species is only iodine-131 if mentioned, otherwise it is all species. No entry means unknown, probably none if underground and "all" if not; otherwise notation for whether measured on the site only or off the site, where known, and the measured amount of radioactivity released.

See also[edit]


  1. ^ Leonard, Zeb (22 May 2014). "Tampering with history: varied understanding of Operation Mosaic". Journal of Australian Studies. 38 (2): 205–219. doi:10.1080/14443058.2014.895956. Retrieved 29 May 2014. 
  2. ^ "Timezone Historical Database". iana.com. Retrieved March 8, 2014. 
  3. ^ a b Cooper, Malcolm B.; Lokan, Keith H.; Williams, Geoffrey A. (November 1, 1983). The Radiological Status of the Monte Bello Islands: May 1983 (PDF) (Technical report). Yallambie, VIC, Australia: Australian Radiation Laboratory. Retrieved December 18, 2013. 
  4. ^ a b Norris, Robert S.; Burrows, Andrew S.; Fieldhouse, Richard W. (1994). Nuclear Weapons Databook, Vol. 5: British, French, and Chinese Nuclear Weapons. Boulder, CO: Westview Press. 
  5. ^ a b Yang, Xiaoping; North, Robert; Romney, Carl (August 2000). CMR Nuclear Explosion Database (Revision 3) (Technical report). SMDC Monitoring Research.