Explorer 4 was launched on July 26, 1958, from Cape Canaveral, Florida, marking a significant milestone in the United States' efforts to explore space. It was part of the Explorer program initiated by the National Aeronautics and Space Administration (NASA) shortly after the Soviet Union's Sputnik launches. The primary objective of Explorer 4 was to study cosmic rays, a challenging area of research that offers insights into high-energy particles from outer space which have implications for both space travel and astrophysics.

The satellite itself was built to measure and record the intensity of cosmic rays in the Earth's upper atmosphere. Constructed with an innovative design, Explorer 4 transmitted data back to ground stations, enabling scientists to begin mapping the distribution and origins of these high-energy particles. The operational success of Explorer 4 represented a technological triumph for the United States during a period of intense competition with the Soviet Union, known as the Space Race.

The successful launch and operation of Explorer 4 underscored the United States' commitment to its space program and served as a catalyst for subsequent missions in the Explorer series, which would further develop satellite technology. Key scientific discoveries from the mission would contribute to the understanding of outer space and lead to future exploratory endeavors, reinforcing the significance of this satellite in the broader narrative of space exploration.