Operation Argus was secretly conducted during August and September of 1958, in the South Atlantic (see: South Atlantic Anomaly), by the US Atomic Energy Commission, in conjunction with the Explorer IV mission. About 1800 km southwest of Cape Town, South Africa the USS Norton Sound, of Top Secret Task Force 88 , launched three modified X-17a missiles armed with 1.7 kt W-25 nuclear warheads into the upper atmosphere, in order to conduct tests regarding the magnetosphere and the Van Allen radiation belts. The tests were proposed by Nicholas Christofilos of the Lawrence Radiation Laboratory (LRL) as a means to determine the possibility of creating artificial radiation belts for military purposes.

The Argus explosions created artificial electron belts resulting from the β-decay of fission fragments. These lasted for several weeks. Such radiation belts affect radio and radar transmissions, damage or destroy arming and fusing mechanisms of intercontinental ballistic missile warheads, and endanger crews of orbiting space vehicles.

The tests were first reported by the New York Times on March 19, 1959. More than 4,500 people participated in the operation. Followed the Hardtack I series, but preceded Hardtack II.

Argus Missile Launches

• Argus I
  • Time: 02:28 August 27, 1958 (GMT)
  • Location: 38.5° South, 11.5° West
  • Altitude: 160 km

• Argus II
  • Time: 03:18 August 30, 1958 (GMT)
  • Location: 49.5 deg South, 8.2 deg West
  • Altitude: 182 Miles

• Argus III
  • Time: 22:13 September 6, 1958 (GMT)
  • Location: 48.5 deg South, 9.7 deg West
  • Altitude: 466 Miles (750 km) (perhaps the highest nuclear explosion ever)
  • Yield: 1.7 kilotons.

See also: Operation Hardtack I