Explorer 6, or S-2, was a NASA satellite, launched on 7 August 1959, at 14:24:20 GMT. It was a small, spheroidal satellite designed to study trapped radiation of various energies, galactic cosmic rays, geomagnetism, radio propagation in the upper atmosphere, and the flux of micrometeorites. It also tested a scanning device designed for photographing the Earth's cloud cover. On 14 August 1959, Explorer 6 took the first photos of Earth from a satellite. Experiments Beacon (108 and 378 MHz) This experiment measured the electron density near the satellite. The observational equipment comprised two coherent transmitters operating at 108 and 378 MHz. Doppler difference frequency and change in Faraday rotation of the 108-MHz signal were observed. Signals were observed from the receiving station at Hawaii for 20 to 70 minutes during each of eight passes during 11 days. Severe fading and a strong magnetic storm added to difficulties in data interpretation. The 378-MHz beacon transmitter failure terminated the experiment. Fluxgate Magnetometer A fluxgate magnetometer was used to measure the component of the magnetic field parallel to the spin axis of the vehicle. The measurements, when combined with those made with the search coil magnetometer (which measured component of the ambient field perpendicular to spin axis of vehicle) and the aspect sensor, where intended to determine the direction and magnitude of the ambient magnetic field. It was intended to obtain measurements at altitudes up to 8 Earth radii, but due to permanent multipole disturbances within the vehicle the fluxgate magnetometer became saturated and returned no data. Thus, information was available from only the search coil and the aspect indicator. Ion Chamber and Geiger–Müller Counter The instrumentation for this experiment consisted of a Neher-type integrating ionization chamber and an Anton 302 Geiger–Müller tube (GM). Due to the complex nonuniform shielding of the detectors, only approximate energy threshold values were available. The ion chamber responded omnidirectionally to electrons and protons with energies greater than 1.5 and 23.6 MeV, respectively. The GM tube responded omnidirectionally to electrons and protons with energies greater than 2.9 and 36.4 MeV respectively. Counts from the GM tube and pulses from the ion chamber were accumulated in separate registers and telemetered by the analog system. The time that elapsed between the first two ion chamber pulses following a data transmission and the accumulation time for 1024 GM tube counts were telemetered digitally. Very little digital data were actually telemetered. The