This is the back-up Pioneer IV instrument package. The conical antenna, lifted here to show the instruments, is made of fiberglass and sprayed with gold. The alternating black and gold stripes help maintain a proper internal temperature by controlling the amount of heat absorbed from sunlight. On the top of the instrument package are two Geiger-Mueller tubes that measured radiation. One is shielded so that only high-energy particles can register. Beneath the tubes is supporting circuitry, a radio transmitter enclosed in a central band of batteries, and, lastly, the lens of a photoelectric scanning device. This lens was designed to trigger a signal to Earth when it
Image Number: 2012-02157
Credit: National Air and Space Museum, Smithsonian Institution
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