Hardtack Teak

HARDTACK-Teak was an exoatmospheric high altitude nuclear weapon test performed during Operation Newsreel. It was launched from Johnston Atoll on a Redstone missile. On , the shot detonated at an altitude of .
Along with HARDTACK-Orange it was one of the two largest high-altitude nuclear explosions.
Planning.
The 3.8-megaton detonation was planned to occur at an altitude of above a point approximately south of Johnston Island. However, due to a programming failure, it burst directly above the island at the desired altitude, making the island the effective ground zero. This brought the explosion nearer the launch site control and analysis crews than intended.
The "Teak" test was originally planned to be launched from Bikini Atoll, but Lewis Strauss, chairman of the United States Atomic Energy Commission opposed the test because of fears that the flash from the nighttime detonation might blind Islanders who were living on nearby atolls. He finally agreed to approve the high-altitude test on the condition that the launch point be moved from Bikini Atoll to the more remote site at Johnston Island.
According to the United States Defense Nuclear Agency report (DNA6038F) on Operation Hardtack I:
Effects.
When the warhead burst at directly above Johnston Island, the flash effectively turned night into day, as shown in the image to the right. The initial glow faded over a period of about 30 seconds. The thermal radiation output of the explosion was such that observers were forced to take cover in the "shade" for the first few moments, as can be seen in film footage of the test.
"Teak" caused communications impairment over a widespread area in the Pacific basin. This was due to the injection of a large quantity of fission debris into the ionosphere. The debris prevented normal ionospheric reflection of high-frequency (HF) radio waves back towards Earth, which disrupted most long-distance HF radio communications. The nuclear detonation occurred at 10:50 UTC on 1 August 1958 (which was 11:50 p.m., Johnston Island local time, on 31 July 1958).
According to the book "Defense's Nuclear Agency 1947–1997", when the "Teak" detonation occurred:
According to page 269 of the Defense Nuclear Agency report on Operation Hardtack:
According to civilian observer reports contained in the official United States Defense Nuclear Agency report on Operation Hardtack I: