Signed Covers: USA 1958 Explorer 1

Explorer 1 launch cover with H.Flick cachet.

The United States joined the Space Race with the launch of Explorer 1 on January 31, 1958, as part of its program for the International Geophysical Year and in reaction to the Soviet Union's launch of Sputnik 1.

Photo: Dr. William H. Pickering, Director of the Jet Propulsion Laboratory from 1954 to 1976. Under his guidance, Pickering's team launched Explorer I aboard a Jupiter-C rocket from Cape Canaveral on January 31, 1958, less than four months after the Soviet Union's launch of Sputnik. During his tenure, JPL achieved numerous successes in space missions, including Explorer, Pioneer, Mariner, Rangers 7-9, Surveyor, and Viking.

Explorer 1, recognized as the first U.S. satellite, is famous for its discovery of the Van Allen radiation belts, which are radiation zones surrounding Earth. The presence of these belts was confirmed through the Explorer 1 and Explorer 3 missions in early 1958, led by Dr. James Van Allen at the University of Iowa. Explorer 1 carried a micrometeorite detector and a cosmic ray experiment designed by Van Allen and his graduate students, with the deployment of the sensor package supervised by Ernst Stuhlinger, who also had expertise in cosmic rays. The data collected from Explorer 1 and Explorer 3 (launched on March 26, 1958) enabled the Iowa team to make the first space-age scientific discovery: the identification of a doughnut-shaped region of charged particle radiation trapped by Earth's magnetic field.

Photo: Professor Ernest Ray (left) and James Van Allen (right) analyze the orbit of Explorer 1.

Explorer 1 launch cover with Goldcraft cachet

Photo: Dr. Wernher Von Braun addresses a news conference, explaining how the Jupiter-C missile successfully launched Explorer 1 into orbit. The Jupiter-C was developed by the U.S. Army Ballistic Missile Agency (ABMA) under von Braun's leadership.