Like so many scientific endeavors, the Pioneer 4 spacecraft wasn’t perfect. When it launched in 1959, it didn’t get close enough to the mysterious lunar surface to study the moon. Nevertheless, it still accelerated science and achieved several important milestones in space exploration.
What Was the Pioneer 4 Spacecraft?
This unmanned spacecraft launched from Cape Canaveral in 1959 to photograph the moon during a close flyby. It was a spin-stabilized vehicle. It had a mechanical despinning mechanism that included weights attached to long wires wrapped around the base of the cone, according to the Smithsonian Air and Space Museum where Pioneer 4 now resides. After the vehicle was on its trajectory, the weights were released to unwind and slow the rate of spin down.
It was a cone-shaped probe that was only 13 pounds and 20 inches (51 cm) high, according to NASA. The probe was made of fiberglass and coated with gold to make it conductive, and was painted with white stripes to help it maintain the proper temperature. A ring of mercury batteries at the base of the cone provided power, and the tip of the cone was a small probe, which, combined with the rest of the cone, acted as an antenna.
The probe was equipped with Geiger counters, which are instruments that measure radiation. A photoelectric sensor poked out of the center of the ring. The sensor had two photocells that were meant to be triggered by moonlight when the probe got close enough to the moon.
The Pioneer 4 spacecraft went down in history as being the first American lunar probe to escape Earth’s gravity and the first American probe to orbit around the sun. It got close to the moon, passing 37,300 miles by the moon’s surface, according to NASA. Unfortunately, this wasn’t close enough — it would need to be 20,000 miles from the moon to trigger the photocell or to measure the moon’s radiation.
A Path to the Moon Landing
The mission didn’t get close enough to capture images or data about the moon itself, but it did bring back excellent data that helped scientists understand the nature of space. It was the first American lunar probe to break out of Earth’s gravity, which was a necessary step toward landing on the moon a decade later.
It was also a valuable exercise in how to track objects in space. Its radio transmitted data for 82 hours and 655,000 miles of travel, according to NASA. This was the farthest distance that anyone had ever tracked a human-made object at the time.
Pioneer 4 sent back excellent radiation data about the Van Allen Belts, which Space.com explains are rings of magnetically trapped, highly energetic charged particles that surround Earth. The data from this mission helped scientists understand the inner and outer structures and varying intensities of different areas of Van Allen Belts.
This knowledge was critical in early space missions and it’s even more important now that we have space vehicles loaded with high-tech, sensitive gear.
“Our current technology is ever more susceptible to these accelerated particles because even a single hit from a particle can upset our ever smaller instruments and electronics,” said David Sibeck, Van Allen Probes mission scientist at NASA‘s Goddard Space Flight Center. “As technology advances, it’s actually becoming even more pressing to understand and predict our space environment.”
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