Introduction:

NASA Ames Research Center and The Planetary Society are celebrating the Silver Anniversary of the launch of the Pioneer 10 Mission with an 25th Anniversary Conference to be held on Monday, March 3, 1997 from 9:00 AM TO 4:30 PM at NASA Headquarters Auditorium

Twenty five years ago on March 2, 1972, Pioneer 10 was launched (A 1.1M QuickTime Clip) from the launch pad at Cape Kennedy, carrying Earth's first space probe to an outer planet. To accomplish this feat, Pioneer 10 had to pass through what was initially feared to be an impenetrable asteroid belt.

After Pioneer 10 emerged through the asteroid belt, Pioneer 11, was launched on a similar trajectory. Pioneer 10 became the first spacecraft to encounter Jupiter. Launch Project Manager, Charlie Hall, (A 4.2M QuickTime Clip) describes mission control at the time of the Jupiter encounter in December, 1973. Pioneer 11 was the first at Saturn. The Pioneer missions paved the way for exploration of the outer solar system.

Now the most remote man-made object launched into the cosmos, Pioneer 10 is approaching nearly 7 billion miles from the Sun. It became the first artifact to "leave the Solar System" on June 13, 1983 when it passed beyond the farthest known planet. It is now searching for the heliopause, exploring the very edges of interstellar space as it drifts onward in mankind's first journey to the stars. (Click on this image for a larger version.)

Along with its sister ship Pioneer 11, Pioneer 10 carries a plaque with messages designed to make contact with possible alien civilizations. The late Dr. Carl Sagan helped devise the plaques that bear the illustration of a man and a woman as well as a diagram identifying earth's location in the galaxy. Like a message in a bottle, these plaques will journey out into interstellar space possibly to be found one day by an extraterrestrial civilization. Dr. Sagan, (A 5.7M QuickTime Clip) discussed the significance of the plaque placed in Pioneer 10 in this interview.

In a series of interviews to commemorate Pioneer 10 on its twenty- fifth anniversary. Dr. Larry Lasher, (A 3.4M QuickTime Clip) Pioneer Project Manager from the NASA Ames Research Center, relates some of the achievements of Pioneer 10. Dr. James Van Allen, (A 3.5M QuickTime Clip) Principal Investigator of the Geiger Tube Telescope instrument, talks about several of the scientific successes of Pioneer 10. The role of the Plasma Analyzer instrument in measuring the solar wind is discussed by its Principal Investigator, Dr. Aaron Barnes, (A 2.7M QuickTime Clip) from the NASA Ames Research Center. Dr. John Simpson, (A 2.9M QuickTime Clip) Principal Investigator of the Charged Particle instrument from the Enrico Fermi Institute of the University of Chicago, discourses on the boundary region of interstellar space.

Pioneer Mission Backgrounder:

Historical Significance: The Pioneer Project Office at NASA Ames Research Center and the Planetary Society are taking the occasion of March 3, 1997 to celebrate the twenty-fifth anniversary of a watershed event in space exploration history: the launch of Pioneer 10.

Some twenty five years ago on March 2, 1972, Pioneer 10 was launched on an Atlas/Centaur launch vehicle from Cape Kennedy carrying Earth's first space probe to an outer planet. To accomplish this feat, Pioneer 10 had to pass through what was feared to be a hazardous asteroid belt. Pioneer 10 demonstrated that this was not the case, thereby opening the door for all future outer planetary missions. After Pioneer 10 emerged from the asteroid belt, its follow-on companion, Pioneer 11, was launched on a similar trajectory. Its purpose was to serve as a backup had Pioneer 10 failed for any reason. After the first ever successful encounter with Jupiter by Pioneer 10, Pioneer 11 was retargeted mid-flight for an eventual encounter with Saturn following the second Jovian encounter in December, 1973

Pioneer 10 led the way for exploration of the outer solar system - paving the way for Pioneer 11, for the Voyagers, for Ulysses, and for the Cassini flight to Saturn in 1997. Pioneer 10 was the first ever to encounter Jupiter survive its intense radiation, and was the first probe to leave the realm of the planets and enter the edges of interstellar space for the first time in history! That major event occurred when Pioneer 10 became the first artifact to "leave the Solar System" on June 13, 1983 when it passed beyond the orbit of farthest known planet. Pioneer 10 is currently over 6 billion miles away with round-trip communications taking over 18 hours at the speed of light of 186,000 mile per second!

Pioneer 10 is now searching for the solar wind termination shock and the edge of interstellar space. It carries with it a plaque heralding a message of its origin to a possible extraterrestrial intelligence that may find it some day.

Extended Mission:

Heliospheric Boundary: The extended mission for Pioneer was to search for the heliopause. The heliopause is the meeting surface of the solar wind and the medium outside the solar environment where the region of interstellar space begins. The solar wind is a 1,600,000 km-per-hour (1,000,000 mph) flow of gases expelled by the sun consisting of protons, electrons, and other subatomic particles. The interstellar medium is of uncertain composition, but the interstellar winds are known to include energetic atomic nuclei whose cosmic flux is detected as far inward as the Earth. An artist's conception of the heliospheric boundaries, (click on the image to the right for a larger version) shows the other spacethat have joined Pioneer 10 and 11 in this search. We can see that only Pioneer 10 is moving in the opposite direction to the Sun's motion through the galaxy, shown here as the solar apex direction. The motion of the heliospheric boundary through the local interstellar medium may cause a bow wave upstream of the heliopause and a tail downstream. The flow of subatomic particles making up the solar wind is expected to undergo a shock transition from supersonic to subsonic before reaching the heliopause. This shock is called the solar-wind termination shock. Here termination refers to the end of supersonic flow and not the end of the solar wind, which occurs at the heliopause. Prior to Pioneers 10 and 11, the effect of the solar wind was thought to extend to the vicinity of Jupiter or perhaps a bit farther. The Pioneer scientists now predict the distance from the Sun at which the terminal shock may be encountered is from 60 to 100 astronomical units (AU) or more, where an AU is defined as the distance of the Earth from the sun ~ 150 million kilometers (~93,000 million miles). For reference, the distance to the outermost planet is ~ 40 AU's.

Star Encounters & Plaque: Several years from now the RTG power will degrade to a level that the signals to Earth will cease, and Pioneers 10 and 11 will coast silently through interstellar space forever.

Included on both spacecraft is the small gold-plated aluminum plaque which the figures of a man and a woman are shown to scale next to a line silhouette of the spacecraft. The bracketing bars on the far right are the representation of the number 8 in binary form (1000), where one is indicated above by the spin-flip radiation transition of a hydrogen atom from electron state spin up to state spin down that gives a characteristic radio wave length of 21 cm (8.3 inches). Therefore, the woman is 8 x 21 cm = 168 cm, or about 5' 6" tall. The bottom of the plaque shows schematically the path that Pioneers 10 and 11 took to escape the solar system - starting at the third planet from the Sun accelerating with a gravity assist from Jupiter out of the solar system. Also shown to help identify the origin of the spacecraft is a radial pattern etched on the plaque that represents the position of our Sun relative to 14 nearby pulsars (i.e., spinning neutron stars) and a line directed to the center of our Galaxy. The plaque may be considered as the cosmic equivalent to a message in a bottle cast into the sea. Sometime in the far distant future, perhaps billions of years from now, Pioneer may pass through a planetary system of a remote stellar neighbor, one of whose planets may have evolved intelligent life. If that life possesses the technical ability and curiosity, it may detect and pick up the spacecraft and inspect it. Then the plaque with its message from Earth may be found and deciphered. The late Dr. Carl Sagan, who helped design the plaque, discusses the significance of the plaque placed in Pioneer 10.

Articles and News Releases

January 28, 1997 NASA Press Release on a recent, successful targeting maneuver.

The November 4, 1996 Issue of: TIME Magazine has an excellent background article on the Pioneer 10 mission and spacecraft.

Pioneer Homepage:

For additional information on Pioneer 10 & 11 and the current status of the missions, visit the Pioneer Project Home Page.