 Square heat-sink units were also mounted on the surface of the sphere to help dissipate heat from the interior.The scientific instruments consisted of an ion chamber and Geiger-Müller tube to measure total radiation flux, a proportional radiation counter telescope to measure high energy radiation, a scintillation counter to monitor low-energy radiation, a VLF receiver for natural radio waves, a transponder to study electron density, and part of the television facsimile system and flux-gate and search coil magnetometers mounted on the instrument platform.The television camera pointed through a small hole in the sphere between two of the solar panel mounts.