Launched on March 2, 1972 by an Atlas-Centaur rocket, Pioneer 10 (also called Pioneer F) was the first spacecraft to travel through the asteroid belt, the first spacecraft to make direct observations of Jupiter, and on June 13th 1983 it became the first man-made object to leave the solar system when it passed the orbit of Neptune (which was then the outermost planet due to the eccentric orbit of Pluto). Pioneer 10 was built by TRW. 
Pioneer 10 on December 3, 1973 sent back the first close-up images of Jupiter.
Famed as the most remote object ever made by man, at last contact Pioneer 10 was over 7.6 billion miles away from Earth. (Until February 17, 1998, the heliocentric radial distance of Pioneer 10 had been greater than that of any other man-made object. But later on that date, Voyager 1's heliocentric radial distance , in the approximate apex direction, equaled that of Pioneer 10 at 69.419 AU. Thereafter, Voyager 1's distance will exceed that of Pioneer 10 at the approximate rate of 1.016 AU per year).
on board the Pioneer spacecraft
The spacecraft made valuable scientific investigations in the outer regions of our solar system until the end of its mission on March 31, 1997. The Pioneer 10's weak signal continued to be tracked by the Deep Space Network as part of a new advanced concept study of chaos theory. Before 1997 the probe was used in the training of flight controllers on how to acquire radio signals from space.
Pioneer 10 is headed in the direction of the star Aldebaran in the constellation Taurus. It will take Pioneer over 2 million years to reach it.
US postage stamp depicting Pioneer 10 passing Jupiter.
On Friday February 28
, scientists at the NASA Jet Propulsion Laboratory
(JPL)'s Deep Space Network in Goldstone, California
, sent a signal to the spacecraft to see if it was still functioning. Pioneer 10 was eleven light hours
away at this point, and so it was twenty-two hours later when researchers at the network's facility in Madrid
, heard Pioneer's response.
A later attempt in December 2002 received a faint response, which was too weak to decode. Pioneer 10's final signal (after two previous failures) was received on January 22, 2003. As of February 25, 2003, NASA came to the conclusion that the craft's radioisotope power source was no longer functioning well enough for further contact with Earth. NASA's Deep Space Network did not detect a signal during the last contact attempt February 7, 2003. The previous three contacts, including the January 22 signal, were very faint with no telemetry received. The last time a Pioneer 10 contact returned telemetry data was April 27, 2002. NASA has no additional contact attempts planned for Pioneer 10.
As of February 5, 2002, Pioneer 10 was 79.66 AU from the Sun. The most recent cosmic ray data from the spacecraft, received on May 19, 2001, showed that the vehicle had not yet reached the heliopause.
Analysis of the radio tracking data from the Pioneer 10 and 11 spacecraft at distances from 20 to 70 AU from the Sun has consistently indicated the presence of an anomalous, small Doppler frequency drift. The drift can be interpreted as a constant acceleration of (8.74 ± 1.33) × 10-10 m/s2 directed towards the Sun. Although it is suspected that there is a systematic origin to the effect, none has been found. As a result, the nature of this so-called Pioneer anomaly has become of growing interest. As of 2004, the difference is said to be about 400,000 km (less than 0.003 AU), roughly the distance between Earth and the Moon.
Last updated: 10-11-2005 14:28:59