Without sanctifying the results through comparison, man's creation of spacecraft "in his own image" follows the example set by God in the creation of man. Only through faith can we hope to assess God's noble reasons for creating man, but we clearly understand why automated spacecraft were devised to help explore the Moon and planets. At the time, they were absolutely essential to do what we wanted to do but were not capable of doing ourselves; our only choice was to devise machines that could go into space in our stead, doing our bidding and performing under our direct control.
It is fitting to note that the evolution of our God-given talents made it possible for us to do the technical things needed for building and operating spacecraft. It is also noteworthy that the spacecraft we have created, while similar to humans in function, do not exhibit the most significant qualities of life. Nevertheless, they have served us well as partners, going forth in the name of our country, seeking answers, and setting precedents for civilized societies now and to follow. While broadening man's horizons, they have also provided a better awareness of our earthly environment and its uniqueness in the universe.
Lest it appear we have overlooked the fact that man himself ventured into space almost at the same time as our robots, I would suggest that the complementary aspects of manned and automated missions typify the trend for the future. Perhaps the inference that automation was devised as a means for exploring until we could go ourselves was true but incomplete-such limited thinking caused an undue polarization of views concerning the merits of manned versus unmanned missions during the first two decades of space exploration. The truth is that there were no such things as unmanned missions; it was merely a question of where man stood to conduct them. In some cases he sent his instruments and equipment into space while controlling them remotely, and in other cases he accompanied them in spacecraft equipped with suitable life support systems. It should be noted that the spurious arguments over the merits of manned versus unmanned missions were never  between machines and men, but between men and men. Perhaps the mere fact that arguments ever occurred over the competitive aspects of manned versus automated missions attests to the potential of robotic partners in space operations.
Now that we have a quarter-century of experience to look back on, it is possible to assess some of the results and contributions made by our exploring machines. Perhaps one of the most significant observations, made by a number of writers, is the fact that the adventures of our automated spacecraft have been enjoyed and shared with mankind in a real-time drama, literally unfolding before millions of eyes. While I have often thought of these missions as similar to the expeditions of great explorers like Lewis and Clark, one beautiful consequence of today's communication systems is the immediacy of sharing the experiences, findings, and results of exploratory missions. I have heard a number of scientists express the feeling of "being there" with Mariners, Surveyors, and the like, for they could associate with those lifelike machines, superposing their own human characteristics, without having to consider "the other human being." Thus, our automated explorers have truly been extensions of man in fulfilling our exploratory desires in a briefer span of time and with broader participation than otherwise would have been possible. They have allowed us experiences that in the past would only have been available to the hardy explorer, without our risking life, limb, and personal resources.
In looking back we fondly recall the additional knowledge of Venus provided by Mariner 2. Its flyby trajectory led to an accurate determination of the planet's mass and orbit, fundamental parametric qualities essential to further scientific studies, if not of particular interest to most people. Still, I think that almost everyone shares somewhat in the pride of knowing that we gained better insight into our nearest planetary neighbor on that first mission. Mariner 2 also gave us our first conclusive information about the dense atmosphere of Venus, including a measure of temperatures at different levels in the clouds. While modest findings in themselves, the close-up data from Mariner enhanced the value of sightings from Earth and from scientific studies employing assumptions now better qualified.
Mariner 5, a somewhat improved descendant of Mariner 2, was transformed from a spare spacecraft to perform another flyby visit to Venus in 1967. Equipped with better instruments, it made definitive measurements of Venus' magnetic field, ionosphere, and radiation belts. It told us much more about the composition of the atmosphere and disappointingly  concluded that Venus had a chemically polluted environment that was at least 750° F near the surface.
Almost 5 years later, the Soviets succeeded in probing the atmosphere with Venera 7, confirming with in situ measurements that carbon dioxide was the predominant constituent. On its way to Mercury, Mariner 10 swung past Venus for another look in 1974, followed shortly by Veneras 9 and 10, which found the surface of the planet to be firm and rocky.
In 1978 the Mariners and Veneras received help from two Pioneers that orbited the planet and fired probes into its surface. The Venus Pioneer was the first spacecraft to be placed in orbit around Venus, supplying a radar map of the surface. A giant rift canyon, the largest ever discovered in the solar system, measured 15 000 feet deep and 900 miles long. In addition to much improved knowledge of the planetwide cloud coverage, Pioneer Venus 1 detected almost continuous lightning activity. Pioneer Venus 2 launched four entry probes 3 weeks before reaching Venus; during entry these probes relayed direct measurements on the structure and composition of the atmosphere. They also provided temperature and pressure profiles, plus tracking data showing deviations in their trajectories which gave indications of Venusian wind velocities. Since that time, visits to Venus have been left to Veneras.
Mercury was looked over well by Mariner 10 during its two-for-one flyby after leaving Venus, using gravitational assistance to change course and velocity. In addition to its first use of a planetary swing-by trajectory to visit another planet, Mariner 10's three encounters with Mercury were of great interest. This feat surely put Mariner 10 in the lead as our most economical and efficient spacecraft. Being closest of any planet to the Sun, Mercury would not even be "a nice place to visit," so it was just as well that Mariner 10 went there for us. We now have answers to many questions concerning Mercury that also help to complete our understanding of solar system mysteries.
Mars was first visited by Mariner 4 in 1965. Although this first successful Mars mission taught us many things, perhaps the most significant was the finding that Mars' surface is pockmarked with craters, much like the Moon. The second finding of great interest was the fact that its atmosphere is very thin, about one-tenth the density of Earth's. Four years later Mariners 6 and 7 told us quite a bit more about Mars' planetary environment and atmosphere, improving knowledge no doubt helpful to the design of the Soviet Mars 3, which landed in 1971 but ceased transmitting 20 seconds after landing.  During the same Mars opportunity Mariner 9 went into orbit while Mars was totally obscured by a gigantic dust storm. After waiting several weeks for the dust to clear, Mariner 9 did a good job of filling us in on details while returning 7300 photographs from orbit. New findings of special note were the huge volcanoes up to 16 miles high and a "grand canyon" over 3000 miles long. Mariner 9 also observed Phobos and Deimos from orbit, giving us our first close-up views of those small satellites of Mars.
Viking orbiters and landers performed so notably while exploring Mars in 1976-83 that, even though their adventures were presented in two earlier chapters, they deserve mention again. The fact that two orbiters, two entry vehicles, and two landers conducted a significant exploratory expedition, sending back detailed information during two Martian years, will be a hard act to follow. Perhaps men will accompany the next robots sent to Mars.
Pioneers 10 and 11 and Voyagers 1 and 2 receive credit for firsthand observations of the asteroid belt, Jupiter, Saturn, and their moons and asteroid rings. The beautiful images returned by these successful craft have not only awed scientists but surely have appealed to the artistic qualities in all who respect the beauty of color and form. There is something inspiring about the giant red spot on Jupiter, more so now that time-lapse images have clearly shown the dynamic nature of this feature. Is there any form more enthralling than beautifully colored Saturn highlighted by its shining, geometrically perfect system of rings? Or is there any more tantalizing object begging scientific examination than Saturn's satellite Titan, the largest moon in our solar system and the only one thought to have oceans and an atmosphere resembling those believed to have existed on Earth during its primitive times? Voyager 1 brought in a flood of findings but is all the more memorable for clearly framing these fantastic questions.
While these summary paragraphs do not do justice to the total achievements of our principal planetary missions, perhaps they will serve to verify our thesis concerning the promise for automated spacecraft and their role as partners to man. None of the missions described could have been done without them, and it may be a long time before we visit all the planets in person-even if we want to.
Since there are powerful arguments for using automated spacecraft to conduct planetary missions, why are there debates among sophisticates regarding the merits for both manned and unmanned missions to the Moon? One reason may be that man, as a generalized "scientific instrument" suited  to exploration and discovery, has not been equalled by any manmade package fitting the same mold. Another reason may be that some see a competition between the two approaches for dollars, manpower, and prestige, causing them to choose sides whether the competition is real or imagined.
In some ways, it was almost ironic that the technologies needed for manned flight evolved concurrently with those needed for automation. Many of the needs were the same; some were not. Of course both modes shared technologies for rockets, guidance, and trajectory control systems; the biggest differences were the one-way nature of automated missions that obviated the Earth return requirement and the life support needs of human flights into space. I believe the emphasis for capable automated missions rested largely on control and communications technologies, whereas requirements for manned missions depended more on solving reentry and environmental control problems. At any rate, the heritage of missilery served to bring capabilities into focus so that manned craft or automated machines offered options or complementary functions in the same decade.
A strong reason to expect the far-term blend of manned flights and automated missions is that increased capabilities in certain functions can be easily achieved with automated systems. For example, machines can have response times much faster than humans; instrumentation derived from extensions of microscope and telescope technologies are obviously superior to man's naked eyes. On the other hand, man's ability to assimilate input data, to retain and properly integrate information, and to reason, plus a significant array of physical capabilities, make him a powerful machine for which there is no equal.
Setting aside that philosophical discussion, let us return to our review of achievements with a look at the missions to the Moon. Here we can see not only the contributions of automated systems, but we can examine the complementary qualities of manned and automated missions with an eye toward future possibilities. For completeness we must recognize that Luna 1 impacted the Moon carrying a Russian medallion and that Luna 3 returned a low-resolution picture of the far side in 1959. It was 5 years later that Rangers 7, 8, and 9 showed close-up details. In 1966, Luna 9 and Surveyor 1 landed, testing the suitability of the surface and topography for Apollo landings Since the findings of Surveyor corroborated the engineering model that had been used for designing the landing gear for the Apollo Lunar Module, it might seem that Ranger and Surveyor missions were unnecessary. Perhaps  this is so, but no one knew at the time. Suppose this had not been the case-how would we have felt today after an Apollo discovery that such. landing could not be made safely?
Even given the acceptability of Surveyor sites, the reconnaissance per formed by Lunar Orbiters greatly facilitated the planning and execution o Apollo missions. Such mapping and topographical data as were made available by Lunar Orbiters would have had to be obtained some other way perhaps at far greater cost and risk. It is also doubtful that the broad area coverage of the Moon would have resulted, since it would not have been mandatory for supporting the Apollo objectives.
There are other complementary aspects of the findings from the several missions. The 13 successful flights of Rangers, Lunar Orbiters, and Surveyors, plus the 8 trips made by Apollo astronauts, combined to teach us many things we would not have known without the combination. The impact in the crater Alphonsus by Ranger 5, the near polar orbit views of Orbiter 5, the landing of Surveyor 7 near crater Tycho in the rugged highlands the visit of Apollo 12 to the Surveyor 3 site, the rover excursions by astronauts gathering broader views and samples to couple with point data, the tremendous benefits from returning lunar samples for examination in laboratories here on Earth-these are but indicators, for there is a long list of synergistic benefits from the combined activities.
Our "obedient" spacecraft have done for us some of the things servants might have done for explorers in the past. They have carried our sensors and equipment where we could not go; they have braved the hostile environments of space and other planets; they have never complained of working hours on end, of being turned off forever when their jobs were done, or even of being sacrificed in the name of science. Fortunately, there is nothing wrong with this treatment of inanimate machines. It encourages me to think that endowing us with the capability to build such "creatures" may be a part of God's plan for helping us rise above slavery.
So far in our conquest of space we have discovered no evidence of living beings. If we view the Moon or Mars as territories for future expansion, then we must plan to establish our bases, dig our mines, build our ports, and perform other necessities without help from "the natives." Today, we might think of colonization through transport of those willing to leave Earth and begin new lives elsewhere. Perhaps the development of territories like Oklahoma and Alaska offer parallels for consideration. On the other hand, during the time the hostile extraterrestrial environments of the Moon and the  planets are being tamed with environmentally suitable habitats for humans, building and other developments might be best done by machines. Like our spacecraft explorers, they would have no concern for the environment and need no consideration regarding hours or working conditions; they might even be perceived as being "perfectly happy" doing our work for us. Men would be present in limited numbers to apply our special qualities as yet unassembled into automatons, but in roles as supervisors and not as laborers. Almost everyone enjoys being a sidewalk superintendent at times-would it not be fun to watch a lunar base being built by a variety of specialized machines?
What can we expect these machines to be like? There is no simple answer, for they will surely take many forms and play many roles. Perhaps some of them will combine the qualities of man and machine, reminding us of the impressions received by Indians upon viewing the Spanish horses and riders of Cortez, which they thought to be some new form of creature. We are accustomed to seeing a man and a bulldozer at work as a team; it is not hard to imagine such a machine operated by its control and communications unit doing the bidding of a distant master. In the 1960s we spoke several times of an idea for dispatching roving vehicles to perform "Lewis and Clark expeditions" on the Moon while under the supervision of scientists and engineers here on Earth. The concept envisioned tuning in on TV from our armchairs to see what was happening each day, to observe findings in near real time, and to direct future actions. Just think how much more rewarding and exciting that would be than shooting at monsters through the medium of a video game!
I also think it is exciting to consider the challenges of developing special-purpose machines to do the many things that can conceivably be done by robots. Already machines are beginning to do things for us on Earth that they can do better than man. Production facilities are ideal for machines, where routine functions like welding, or assembling parts, painting, or inspecting can be performed precisely by preprogrammed systems. These tasks do not need the higher order of intelligence possessed by man, and the substitution of machines for men in these instances frees minds for more creative ventures. There are many functions to be performed by robots, and as our capabilities to engineer these systems advance, it should be expected that we will improve our machines by giving them more "brainpower."
Already many stories can be told about the uncanny actions of control system processors which had been programmed to perform complex  functions. An example comes to mind from Viking that occurred well into the mission, when Mars was approaching full conjunction; that is, when Mars and Earth were about to be on completely opposite sides of the Sun, so that the Viking orbiters not only became blocked from view by Mars during each orbit, but would also be eclipsed by the Sun. The event that triggered Viking Orbiter 1 into an argument with itself was its not being able to see either the Sun or Earth. The problem became apparent to controllers when the orbiter reappeared and its S-band data stream was missing. The X-band link was strong and nominal, and since it made use of the Earth-pointed S-band antenna for some applications, it seemed likely that the orbiter was still oriented properly.
The low-gain link was checked next, for the spacecraft had been programmed to switch to the low-gain mode if the high-gain link were lost for any reason. High-gain data could miss Earth with even slight pointing errors of the orbiter, for example, but low-gain data could be received on Earth even when the spacecraft was well out of alignment (the reason for this kind of automatic emergency procedure). The search sweep quickly located the low-gain data stream, and it was then possible to acquire the engineering information needed to examine the problem.
The problem was traced to the two data processors associated with the orbiter's computer. These processors were programmed to recognize the Sun as an attitude control reference, and they reacted to the loss of the reference by "safing" the spacecraft with an emergency routine that included spacecraft shutdown events, search activities, and the S-band data transmission transfer from high gain to low gain. This procedure was needed to prevent the spacecraft from performing incorrect maneuvers and going out of control if an onboard failure caused the loss of a navigational reference-like the Sun.
When it was known in advance that a natural reference loss such as a Sun occultation was going to occur, the processors had to be told to disregard the loss and inhibit the safing routine. Both processors had been told to disregard the loss of the Sun during solar occultation, but processor B somehow forgot. The result was that B thought something was wrong with A when A did the right thing by disregarding the loss of the Sun. By design, the processor that sensed a problem (or thought it had) became the priority processor. Consequently, when B decided that A was wrong for not reacting with an emergency response to the loss of the Sun, it took charge and shut A off. This story was quickly reconstructed after the low-gain data rate was  precisely adjusted by command from Earth, but there was a bit of finesse involved in getting processor B to relinquish control to processor A. The reason was that orbiter processors were designed so that they could not be simply commanded off; engineers actually "fooled" processor B into relinquishing control by deliberately sending it commands which caused it to err; the stored program then automatically switched to A.
We have much to learn about the use of computer processors, as our efforts to date have produced systems far more limited and primitive than many of those possessed by simple creatures all around us. Who can explain the mysteries of the navigation systems used by migratory birds and turtles sufficiently to allow modeling their systems for use in spacecraft? How is it that tiny insects are capable of attitude stabilization within the limits of their weight and volume? How can the blend of chemical, electrical, and mechanical systems present in most creatures teach us to apply similar principles to our machines? Surely we have a long way to go.
From the meager capabilities of the CC&S of Mariner 2, we now find Voyager spacecraft with 27 processors; not only are they performing individual chores, but computers are actually supervising other computers in distant space. This is effective because the supervisory functions require realtime information and rapid responses that humans directing operations from Earth cannot provide. The long time delay between sending commands and receiving acknowledgment from distances of over 500 million miles is an absolute to be reckoned with. Of course, this application of computer supervision places a burden of responsibility on the engineers who have to provide onboard logic and preprogrammed intelligence to send on the mission. The learning ability ascribed to computer applications has been limited, so the necessary background and experience to be used in flight must, for the most part, be anticipated and provided in advance by the humans in charge.
John Casani, Galileo Project manager at JPL, recently told me about engineers sending a load of commands to a Voyager spacecraft on its way to Saturn Voyager acknowledged receipt of the commands, but replied that it would not execute them as sent, for they would produce unwanted consequences This seemingly mutinous response was at first alarming. Days later, after detailed study and simulations, a mistake was found in the command series that the spacecraft had properly detected, even though it had been overlooked by its makers. Fortunately, the thoroughness of their preprogramming had exceeded the quality of checkout applied to en route instructions.
 However future chapters of history may be written, it is clear that the spacecraft used in our initial exploration of the Moon and planets were effective prodigies-forerunners of a new age. As automatons become more important in our society, the heritage of early electromechanical Mariners, Rangers, and other spacecraft will assume more significance.
Future applications of such sophisticated technologies will remain as reflections of their masters-either good or evil. Thus far automated spacecraft have always served as partners to man, "for the benefit of all mankind." How their descendants serve will depend on the nobility of man.