An Interesting Article about the Voyage Space Probes – Ed O’Rourke

This Scientific American article is long, no surprise there.  It is also interesting.  I invite you to see these excerpts and then read the entire article.



This coincidence meant that a space vehicle could get a speed boost from the gravitational pull of each giant planet it passed, as if being tugged along by an invisible cord that snapped at the last second, flinging the probe on its way. Flandro calculated that the repeated gravity assists, as they are called, would cut the flight time between Earth and Neptune from 30 years to 12. There was just one catch: the alignment happened only once every 176 years. To reach the planets while the lineup lasted, a spacecraft would have to be launched by the mid-1970s.

 After nearly 45 years in space, they are still functioning, sending data back to Earth every day from beyond the solar system’s most distant known planets. They have traveled farther and lasted longer than any other spacecraft in history. And they have crossed into interstellar space, according to our best understanding of the boundary between the sun’s sphere of influence and the rest of the galaxy. They are the first human-made objects to do so, a distinction they will hold for at least another few decades. Not a bad record, all in all, considering that the Voyager missions were originally planned to last just four years.

So NASA’s engineers equipped the vehicles’ computers with 69 kilobytes of memory, less than a hundred thousandth the capacity of a typical smartphone. In fact, the smartphone comparison is not quite right. “The Voyager computers have less memory than the key fob that opens your car door,” Spilker says. All the data collected by the spacecraft instruments would be stored on eight-track tape recorders and then sent back to Earth by a 23-watt transmitter—about the power level of a refrigerator light bulb. To compensate for the weak transmitter, both Voyagers carry 12-foot-wide dish antennas to send and receive signals.

“The only active volcanoes we knew of at the time were on Earth,” says Edward Stone, who has been the project scientist for the Voyager missions since 1972. “And here suddenly was a moon that had 10 times as much volcanic activity as Earth.” Io’s colors—and the anomalous ions hitting Krimigis’s detector—came from elements blasted from the moon’s volcanoes. The largest of Io’s volcanoes, known as Pele, has blown out plumes 30 times the height of Mount Everest; debris from Pele covers an area about the size of France.

Altogether, the Voyagers took more than 33,000 photographs of Jupiter and its satellites. It felt like every image brought a new discovery: Jupiter had rings; Europa, one of Jupiter’s 53 named moons, was covered with a cracked icy crust now estimated to be more than 60 miles thick. As the spacecraft left the Jupiter system, they got a farewell kick of 35,700 miles per hour from a gravity assist. Without it they would not have been able to overcome the gravitational pull of the sun and reach interstellar space.

Record-Breaking Voyager Spacecraft Begin to Power Down

The pioneering probes are still running after nearly 45 years in space, but they will soon lose some of their instruments

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