Exploring the Solar System

Exploring the Outer Planets

What were the first Pioneer probes?

The first three Pioneer probes were drum-shaped spacecraft weighing eighty-four pounds (thirty-eight kilograms) each. They were intended to go into orbit around the Moon. Too bad they failed to leave Earth’s gravity. Pioneer 4 was a much smaller payload at just thirteen pounds (six kilograms), and was designed to fly by the Moon rather than orbit it. Pioneer 4 was successfully launched out of Earth’s gravitational pull, and passed within thirty-seven thousand miles (sixty thousand kilometers) of the Moon, but it was too far away to gather any scientific data. Four more moon probes were unsuccessful, too.


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