On July 9, 1962, at 09:00:09
Coordinated Universal Time (11:00:09 p.m. on July 8, 1962,
Honolulu time), the Starfish Prime test was detonated at an altitude of 250 miles (400 km). The coordinates of the detonation were
16°28′N 169°38′WCoordinates:
16°28′N 169°38′W.
[1](p4) The actual weapon
yield came very close to the design yield, which various sources have set at different values in the range of 1.4 to 1.45
Mt (5.9 to 6.1
PJ). The nuclear warhead detonated 13 minutes 41 seconds after liftoff of the Thor missile from Johnston Atoll.
[5]
Starfish Prime caused an
electromagnetic pulse (EMP) that was far larger than expected, so much larger that it drove much of the instrumentation off scale, causing great difficulty in getting accurate measurements. The Starfish Prime electromagnetic pulse also made those effects known to the public by causing electrical damage in Hawaii, about 898 miles (1,445 km) away from the detonation point, knocking out about 300 streetlights,
[1](p5) setting off numerous burglar alarms, and damaging a telephone company
microwave link.
[6] The EMP damage to the microwave link shut down telephone calls from
Kauai to the other
Hawaiian islands.
[7]