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Starfish Prime was a high-altitude nuclear test conducted by the United States, a joint effort of the Atomic Energy Commission (AEC) and the Defense Atomic Support Agency. It was launched from Johnston Atoll on July 9, 1962, and was the largest nuclear test conducted in outer space, and one of five conducted by the US in space.
A Thor rocket carrying a W49 thermonuclear warhead (designed at Los Alamos Scientific Laboratory) and a Mk. 2 reentry vehicle was launched from Johnston Atoll in the Pacific Ocean, about west-southwest of Hawaii. The explosion took place at an altitude of , above a point southwest of Johnston Atoll. It had a yield of . The explosion was about 10° above the horizon as seen from Hawaii, at 11 pm Hawaii time.
In 1958, the United States had completed six high-altitude nuclear tests that produced many unexpected results and raised many new questions. According to the U.S. Government Project Officer's Interim Report on the Starfish Prime project:
The Starfish test was originally planned as the second in the Fishbowl series, but the first launch (Bluegill) was lost by the radar tracking equipment and had to be destroyed in flight.
The initial Starfish launch attempt on June 20 was also aborted in flight, this time due to failure of the Thor launch vehicle. The Thor missile flew a normal trajectory for 59 seconds; then the rocket engine stopped, and the missile began to break apart. The range safety officer ordered the destruction of the missile and warhead. The missile was between in altitude when it was destroyed. Parts of the missile and some radioactive contamination fell upon Johnston Atoll, nearby Sand Island, and the surrounding ocean.
A total of 27 small rockets were launched from Johnston Atoll to obtain experimental data from the Starfish Prime detonation. In addition, a large number of rocket-borne instruments were launched from Barking Sands, Kauai, in the Hawaiian Islands.United States Department of Defense. Report ADA955411. "A Quick Look at the Technical Results of Starfish Prime". August 1962.
A large number of United States military ships and aircraft were operating in support of Starfish Prime in the Johnston Atoll area and across the nearby North Pacific region.
A few military ships and aircraft were also positioned in the region of the South Pacific Ocean near the Samoan Islands. This location was at the southern end of the magnetic field line of the Earth's magnetic field from the position of the nuclear detonation, an area known as the "southern conjugate region" for the test. An uninvited scientific expeditionary ship from the Soviet Union was stationed near Johnston Atoll for the test, and another Soviet scientific expeditionary ship was in the southern conjugate region near the Samoan Islands.United States Central Intelligence Agency. National Intelligence Estimate. Number 11-2A-63. "The Soviet Atomic Energy Program" , p. 44.
After the Starfish Prime detonation, bright auroras were observed in the detonation area, as well as in the southern conjugate region on the other side of the equator from the detonation. According to one of the first technical reports:
These auroral effects were partially anticipated by Nicholas Christofilos, a scientist who had earlier worked on the Operation Argus high-altitude nuclear shots.
According to U.S. atomic veteran Cecil R. Coale,Schwoch, James. Global TV: New Media and the Cold War, 1946–69 (Illinois, 2009). Web. Accessed March 19, 2012. some hotels in Hawaii offered "rainbow bomb" parties on their roofs for Starfish Prime, contradicting some reports that the artificial aurora was unexpected.
"A 'Quick Look' at the Technical Results of Starfish Prime" (August 1962) states:
A 2006 report described the particle and field measurements of the Starfish diamagnetic cavity and the injected beta flux into the artificial radiation belt. These measurements describe the explosion from 0.1 milliseconds to 16 minutes after the detonation.
The airglow observation program was part of upper atmosphere research directed by Dr. C. Ellyett.
On July 9, 1962, Samuel Neff and his wife Ruth Neff were at the Rolleston field station to operate the photometer and record any observations. Photometric results were published in the Journal of Geophysical Research Letters. Christchurch is on approximately the same longitude as Johnston Island, but is much further from the equator, consequently, the earth’s magnetic lines of force entering the atmosphere near Christchurch were assumed to be too far above Johnston Island for there to be much linkage between Christchurch and the explosion. This assumption proved to be false.
Five to ten seconds after the explosion white auroral shafts were seen to emanate from the magnetic zenith. Within one minute these shafts had taken on a reddish tinge, and by 9:04 (GMT) the white structure was dominated by a red glow that covered most of the sky to the north and extended past the zenith to the south. The display of light was visible to the naked eye for about twelve minutes, though photometric values of intensity stayed above normal for more than an hour.
The photometer was designed to measure specifically the atomic emissions from the ground configuration of the Oxygen atom resulting from 1S to 1D transitions (557.7 nm) and 1D to 3P transitions (630.0 nm). Both these emissions are components of the normal airglow and auroras. Measurements showed a maximum for 557.7 nm of 2x104 rayleighs about two minutes after detonation. This value was approximately 200 times the normal airglow value. The maximum for 630.0 nm was 1.8x105 rayleighs, or 2.4x103 times the normal value, corresponding to a class 3 aurora. The peak intensity came 4 minutes after detonation, the delay relative to 557.7 nm arising from the longer lifetime of the 1D state. The emission from the 1D state dropped in a strictly exponential manner for 7 minutes, allowing an accurate measurement of the decay constant for that state. The resulting value (.0087sec−1) is in close agreement with the value of .0092 sec−1 calculated theoretically by Garstang.
At the time of the explosion an ionosonde was recording at Godley Head, about 15 miles from Christchurch. Geoff King and Harvey Cumack, of the Geophysical Observatory, (DSIR), Christchurch, combined the observed ionospheric and photometric results to gain insight into the mechanisms that could explain the visual observations. Though the ionosonde data was severely distorted, King and Cumack were able to obtain the electron density in the f region at four minutes after the explosion. Excitation of the 1D state of oxygen in the airglow and aurora is satisfactorily explained by a process of dissociative recombination, for which most rate coefficients are known. King and Cumack were able to show that the intensity of 630.0 nm radiation measured by Neff was orders of magnitude greater than that which would be produced by recombination. The remaining possibility was that following the explosion, a wave of neutral plasma (ions plus electrons) entered the atmosphere over Christchurch with sufficient density and energy to produce the observed excitation through electron-atom collisions. These results were published in the New Zealand Journal of Geodesy and Geophysics, in December, 1962.
In 1963, it was reported that Starfish Prime had created a belt of MeV electrons. In 1968, it was reported that some Starfish electrons had remained in the atmosphere for 5 years.In The Radiation Belt and Magnetosphere.
A year after the test, in 1963, the US and USSR signed the Partial Nuclear Test Ban Treaty, which banned all above-ground nuclear testing. France and China continued above-ground tests for a few more decades.
Accurate determination of the decay constant for the 1D state of the ground configuration of the oxygen atom.
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