An unmanned American spacecraft. It was the first probe to pass through the asteroid belt and the first to pass by the planet Jupiter and the first man-made object to leave the Solar System.

It was launched on March 2, 1972. At the time knowledge of the asteroid belt was fuzzy and many thought it to be impenetrable. It made it through without a hitch and went on to a very successful flyby through the Jovian system, achieving its closest approach of 200,000 km (that's 2.8 Jovian radii) above the cloud tops on December 3, 1973.

After its encounter with Jupiter the probe was flung via gravity assist into a flight path in the general direction of the star Aldebaran in the constellation Taurus. Nearly ten years later on June 13, 1983 the craft crossed the orbit of the farthest known planet and thus officially "left the Solar System" as we now know it. The probe continued to be tracked in the succeeding years, in the hopes of detecting the heliopause, the outer boundary of the Sun's magentosphere. At current speed the probe will pass by Aldebaran in 2 million years.

In the event that extraterrestrial intelligent life encounters the spacecraft in some future eon, a gold-plated aluminum plaque designed by Carl Sagan was installed on it. It includes figures of a nude man and woman in scale next to a line drawing of the spacecraft. Also included is a map of the solar system and the path the probe took to escape it, as well as a radial pattern that maps the relative position of the Sun to 14 nearby pulsars and the center of the Milky Way.

The spacecraft experienced a gravitational deflection in 1992 when it was at about 56 AU from the Sun. This may have been caused by a previously unknown Kuiper Belt object.

Pioneer's scientific mission was officially ended on March 31, 1997. Its signal was still detectable and continued being tracked by the Deep Space Network as part of a chaos theory experiment. Data from its Geiger Tube Telescope instrument continued to be analyzed by James Van Allen (yes, the guy who the Van Allen Belts are named after) in the hopes of finding the heliopause.

For a time thought dead after radio contact was lost in October 2000, Pioneer 10's signal was reacquired by a DSN station in Madrid on April 28, 2001. It was contacted again on March 2, 2002, its 30th anniversary, and found to be in continued good health.

Pioneer 10 was officially declared lost on February 26, 2003. No further attempts will be made to communicate to the craft or listen for a signal. The last radio signal detected from the spacecraft was received on January 22, 2003. On February 7, 2003 a last contact attempt failed to find a detectable signal. The end was not a surprise, Pioneer's last transmission with telemetry data was April 27, 2002. Two succeeding transmissions were very faint and contained no telemetry. It is believed that its radioactive power source has degraded to the point where it was no longer strong enough to run the craft's systems and produce a radio signal strong enough to be detectable on Earth.

Pioneer 10 will greet interstellar space in silence, leaving the likely honor of finding that boundary to either Voyager 1 or Voyager 2.

Companion to Pioneer 11.

Mission Status of as February 26, 2003:

  • Distance from Sun: 82.24 AU
  • Distance from Earth: 12.23 billion km
  • Speed relative to Sun: 12.224 km/sec
  • Round Trip Light Time: 22 hours 40 minutes
  • Final Radio Contact: January 22, 2003

Check for the latest Pioneer status updates.

The art historian Ernst Gombrich offers an insightful commentary on the plaque carried by Pioneer 10:

The National Aeronautics and Space Administration has equipped a deep-space probe with a pictorial message 'on the off-chance that somewhere on the way it is intercepted by intelligent scientifically educated beings.' It is unlikely that their effort was meant to be taken quite seriously, but what if we try? These beings would first of all have to be equipped with 'receivers' among their sense organs that respond to the same band of electromagnetic waves as our eyes do. Even in that unlikely case they could not possibly get the message. Reading an image, like the reception of any other message, is dependent on prior knowledge of possibilities; we can only recognize what we know. Even the sight of the awkward naked figures in the illustration cannot be separated in our mind from our knowledge. We know that feet are for standing and eyes are for looking and we project this knowledge onto these configurations, which would look 'like nothing on earth' without this prior information. It is this information alone that enables us to separate the code from the message; we see which of the lines are intended as contours and which are intended as conventional modelling. Our 'scientifically educated' fellow creatures in space might be forgiven if they saw the figures as wire constructs with loose bits and pieces hovering weightlessly in between. Even if they deciphered this aspect of the code, what would they make of the woman's right arm that tapers off like a flamingo's neck and beak? The creatures are 'drawn to scale against the outline of the spacecraft,' but if the recipients are supposed to understand foreshortening, they might also expect to see perspective and conceive the craft as being further back, which would make the scale of the manikins minute. As for the fact that 'the man has his right hand raised in greeting' (the female of the species presumably being less outgoing), not even an earthly Chinese or Indian would be able to correctly interpret this gesture from his own repertory.

(Gombrich, The Visual Image,1974).

The representation of humans is accompanied by a chart: a pattern of lines beside the figures standing for the 14 pulsars of the Milky Way, the whole being designed to locate the sun of our universe. A second drawing (how are they to know it is not part of the same chart?) 'shows the earth and the other planets in relation to the sun and the path of Pioneer from earth and swinging past Jupiter.' The trajectory, it will be noticed, is endowed with a directional arrowhead; it seems to have escaped the designers that this is a conventional symbol unknown to a race that never had the equivalent of bows and arrows.

(Gombrich, The Image and the Eye: Further Studies in the Psychology of Pictorial Representation, London 1982).

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