Geek Trivia: Pioneer and far

What is the scientific mystery known as the Pioneer Anomaly, a physics-defying conundrum that is named in part after the Pioneer 10 space probe?

In many cultures, Friday the 13th is occasionally considered bad luck, but at least for 2008, Friday, June 13 will mark a momentous (if only mildly inaccurate) anniversary. On June 13, 1983, the space probe Pioneer 10 became the first man-made object to leave the solar system... sort of.

What Pioneer 10 actually did on that date was pass into trans-Neptunian space, beyond the reach of the farthest known planet (be that planet Neptune or Pluto, for those of you who refuse to stop calling the latter a bona fide planet). That's not technically the end of the solar system, as there's always the Oort Cloud containing the most distant (about one light year away) objects still in orbit of our sun, and the heliopause, where the power of our sun's solar winds give way to the thrust of stellar wind.

Pioneer 10 is nowhere near reaching either of these boundaries, but it was the first human construct to leave the planetary zone of our local space behind and brave the wilds of the Kuiper Belt, so June 13, 1983 is a significant astronautic date regardless of the media's mislabeling the event. Pioneer 10 is also still occasionally referred to as the most distant man-made object in existence, but while the probe did once hold that title, Voyager 1 overtook it on February 17, 1998 and -- barring some external intervention -- will be the more far-flung human construct for the foreseeable future.

Rather than focus on what Pioneer 10 is not, let us remember what it was and is: One of the most historically significant and technically accomplished spacecraft ever built. Pioneer 10 was the first probe to get up close and personal with Jupiter, sending back the first highly detailed photos of the Jovian gas giant in 1973. In 1997, after its official mission profile was completed, Pioneer 10 became a training article for space probe flight controllers, so they could learn how to acquire radio signals from weak and distant sources. At the same time, Pioneer 10's telemetry readings became component data in a Deep Space Network study into chaos theory.

Thus, for various purposes, Pioneer 10 was tracked continuously from its launch in 1972 until it broadcast its last known signal in 2003. From that vast data set, a physics-defying mystery emerged that continues to intrigue and baffle scientists to this day. It's known appropriately as the Pioneer Anomaly.


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