The Sputnik 3 completion date kept slipping and Sergei Korolev substituted the relatively simple Sputnik 1 as the first satellite to be launched, instead. The Sputnik 2 was also ready earlier and launched earlier than Sputnik 3. Korolev was concerned that if he waited for Sputnik 3 to be ready, the United States would be the first to launch an artificial satellite.
The scientific instrumentation (twelve instruments) 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. The outer radiation belts of the Earth were detected during the flight. Its tape recorder failed, so it could not map the Van Allen radiation belt. The spacecraft remained in orbit until April 6, 1960, when the orbit degraded from drag in upper atmosphere to the point causing the satellite to enter the atmosphere.
