Pioneer 10

Pioneer 10 (also called Pioneer F) was the first spacecraft to travel through the asteroid belt, and was the first spacecraft to make direct observations of Jupiter. It was launched on March 2, 1972 by an Atlas-Centaur rocket.

Mission

On December 3, 1973, Pioneer 10 sent back the first close-up images of Jupiter. On June 13th 1983 it passed the orbit of Neptune, then the outermost planet because of Pluto's highly eccentric orbit. By some definitions, this made the spacecraft the first artificial object to leave the solar system. However, Pioneer 10 has still not passed the heliopause or Oort cloud.

Famed for a time as the most remote object ever made by man, at last contact Pioneer 10 was over 7.60 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). As of December 30, 2005 Pioneer 10 was 89,7 AU away from the Sun.

Pioneer 10 was also outfitted with a plaque to serve as a message for any extraterrestrial life, in the unlikely case that it may be discovered.

Built by TRW [1], 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.

The last, very weak, signal from Pioneer 10 was received January 23, 2003. A contact attempt February 7, 2003, was not successful and further attempts are not planned. The last successful reception of telemetry was on April 27, 2002; subsequent signals were barely strong enough to detect. Loss of contact was probably due to a combination of increasing distance and the spacecraft's steadily weakening power source, rather than failure of the craft.

However, the planetary society mentions in their Pioneer Anomaly pages that there will be one last attempt to get data from the spacecraft on March 4, 2006. After this date the spacecraft antenna will never be aligned correctly again.

Pioneer 10 is heading in the direction of the star Aldebaran in the constellation Taurus. It will take Pioneer over 2 million years to reach it.

Pioneer anomaly

Analysis of the radio tracking data from the Pioneer 10 and 11 spacecraft at distances between 20–70 AU from the Sun has consistently indicated the presence of an anomalous, small Doppler frequency drift. The drift can be interpreted as being due to 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 anomaly has become of growing interest.