 Sputnik 3 was launched on May 15, 1958, and carried a large array of instruments for geophysical research and provided data on pressure and composition of the upper atmosphere, concentration of charged particles, photons in cosmic rays, heavy nuclei in cosmic rays, magnetic and electrostatic fields, and meteoric particles.After a series of failures with the program, the US succeeded with Explorer 1, which became the first US satellite in space, on February 1, 1958.This carried scientific instrumentation and detected the theorized Van Allen radiation belt.