[vi] THERE ARE CERTAIN human enterprises that seem, from the very beginning, to be touched with a certain elan that distinguishes them from others. Those of us who have had the pleasure to be associated with the Pioneer project have long felt that it belongs in this group. There is about Pioneer 10 and 11 a simplicity in concept and an elegance in design and execution that clearly transcends the ordinary.
These Pioneer spacecraft are unique: Pioneer 10 is the first spacecraft to fly beyond the orbit of Mars and through the Asteroid belt, it made the first series of "in situ" measurements of Jupiter's environment, it provided the first close-up pictures of the giant planet and finally, Pioneer 10 is the first man-made object to leave the solar system. Pioneer 11 is the first spacecraft to fly to the ringed planet Saturn.
In spite of the essential simplicity of the Pioneer spacecraft, highly sophisticated scientific experiments were performed. The first direct measurements of Jupiter's magnetic field and of the charged particles trapped in the field were performed. A thermal map of Jupiter was obtained and information about the composition of the planet's upper atmosphere was secured. The trajectory of Pioneer 10 was such that the spacecraft was occulted by the satellite lo which provided the first direct evidence of the very tenuous atmosphere that surrounds lo by observing the direct alteration of the telemetry signal carrier wave. The trajectory of Pioneer 11 provided the first pictures of the polar regions of the giant planet. These results, as well as many others, are explained in more detail in this volume.
It would be a mistake to dwell only on the scientific results of these Pioneers without mentioning the engineering achievements. Both spacecraft have transmitted information over telemetry links for distances that are by now almost an order of magnitude larger than those transmitted by any previous spacecraft. The radioisotope thermoelectric power supplies aboard Pioneer are more efficient and longer lasting than previous designs. Finally, the integration and the management of the large number of diverse experiments was an important engineering achievement.
[vii] This Pioneer project proved that a complex and sophisticated planetary exploration mission can be carried out at a relatively moderate cost. It is likely that the management of future planetary missions will follow some of the methods that were developed by the Pioneer project. This is especially important in view of the fact that funds for exploration projects of this kind are likely to become much harder to obtain in the coming years.
In spite of the obvious importance of the scientific results, the engineering achievements and the management techniques, the meaning of Pioneer transcends them in importance. The Pioneer mission to the outer planets is a symbol of human aspirations. To reach out, to explore, to satisfy the curiosity, that is what is really important. Pioneer proves once again that we can move in the right direction and that real achievements are possible. This volume is a tribute to those who worked so hard to demonstrate this point.