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The Space Age began with the October 4, 1957 launch of Sputnik, the world’s first artificial satellite, by the Soviet Union.
Sputnik ushered in a new era of political, scientific and technological achievements that became known as the Space Age.
Explorer I was America’s successful response to Sputnik.

The U.S. Army Ballistic Missile Agency, or ABMA, was formed at Redstone Arsenal February 1, 1956, to develop the Army’s first offensive ballistic missiles. It was commanded by General John Medaris with Wernher von Braun serving as its technical director. Following the launch of the Soviet satellite Sputnik 1 on October 4, 1957, and the failure of the U.S. Vanguard TV3 satellite in December 1957, ABMA’s effort using modified Redstone - Jupiter C rockets was revived to catch up with the Soviet Union; and Jupiter C placed the Explorer I satellite in orbit on January 31, 1958. In March 1958, ABMA was placed under the new Army Ordnance Missile Command (AOMC) commanded by General Medaris. On July 1, 1960, the AOMC space-related missions and most of its employees, facilities, and equipment were transferred to NASA, forming the George C. Marshall Space Flight Center (MSFC). Wernher von Braun was named MSFC director.

The photograph shows “from left to right, (seated) Dr Eberhard Rees, Major General John B. Medaris, Germanborn rocket scientist Wernher von Braun, Dr Ernst Stuhlinger, (standing) Willi Mrazek and Dr Walter Haeussermann. The model which is actual size shows the assembled scientific Earth satellite and the final stage rocket which will orbit together as a single unit” (ABMA caption).

Explorer I was designed and built by the California Institute of Technology’s JPL under the direction of Dr. William H. Pickering and Dr. James A. Van Allen, who designed and built the scientific instruments which detected the Van Allen radiation belt.

“There is beauty in space, and it is orderly. There is no weather, and there is regularity. It is predictable. Just look at our little Explorer; you can set your clock by it—literally; it is more accurate than your clock. Everything in space obeys the laws of physics. If you know these laws, and obey them, space will treat you kindly. And don’t tell me man doesn’t belong out there. Man belongs wherever he wants to go—and he’ll do plenty well when he gets there.”
Wernher von Braun (Time Magazine, February 17, 1958)

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The successful launch of the American satellite Explorer I marked the official entry of the United States in the Space Age and the Space Race with the Soviets.

Explorer I was launched on a Jupiter C rocket designed by von Braun’s team at the US Army Ballistic Missile Agency (ABMA) after the failure of Vanguard TV3 two seconds after liftoff on December 6, 1957. The satellite detected the Van Allen radiation belt, returning data until its batteries were exhausted after nearly four months.

“We have now established our foothold in space, we will never give it up again,” said Wernher von Braun after the successful launch and signal acquisition (https://www.army.mil/article/199846/celebrating_the_armys_explorer_1_legacy).

“We have now established our foothold in space, we will never give it up again.”
Wernher von Braun