Van Allen radiation belt
Sputnik 3 included twelve scientific instrumentation that 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 onboard Tral-D tape recorder, intended to store data for later transmission to Earth, failed limiting data to what could be gathered while the satellite was directly visible from ground. Because of this failure Sputnik 3 was unable to map the Van Allen radiation belt.