 A thermally sensitive coil was attached to the blades in such a way that low temperatures within the satellite would cause the coil to contract and rotate the blades and expose the heat absorbing surface, and high temperatures would cause the blades to cover the black patterns.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 scintillation spectrometer to study the Earth's (and possible lunar) radiation belts, a VLF receiver for natural radio waves, a transponder to study electron density, and part of the flux-gate and search coil magnetometers mounted on the instrument platform.