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On Mars: Exploration of the Red Planet. 1958-1978



INTRODUCTION



[xi] For many members of the Viking flight team, the early morning hours of 20 July 1976 were the culmination of 8 years of intense activity. Several of the scientists had more than 15 years invested in preparations for the investigations that would begin once Viking safely landed on the surface of Mars. The focus of everyone's attention on this day was the Viking I spacecraft in orbit around Mars. Across 348 million kilometers, the team maintained contact with the 3250-kilogram craft from the Jet Propulsion Laboratory (JPL) in Pasadena, California. JPL this night stood jewellike, its brightly lit buiIdings contrasting sharply with the darkened silhouette of the San Gabriel Mountains. Outside the Theodore von Karman Auditorium, converted into a press center for the mission, mobile television vans were being readied to broadcast the news of Viking's success or failure.

While reporters prepared stories and visitors strolled over the grounds, members of the flight team could be seen on the closed-circuit television monitors as they sat in the half-light of the control room. Elsewhere, hundreds of engineers, scientists, technicians, and support crews were at work or waiting to go to work. At 1:52 a.m., PDT, the audio circuit on the JPL television came to life, and George Sands, associate project scientist and for the moment the "Voice of Viking," announced: "We have separation.... We have engineering data indicating separation....Separation is being confirmed all along the line." Eighteen minutes 18 seconds earlier, the time it took the confirming radio signal to travel from Mars to Earth, the lander had separated from the orbiter. ¹

By 2 a.m., the noise that had been building up at the press center and in the visitor areas diminished. Mission control, a small, glass-walled room with men seated around a circular console watching data displayed on television screens, was being projected on monitors around the lab. "Beyond the controllers' desks and the consoles, through the glass walls of his office.... [was] Jim Martin, a big man in a short-sleeved blue shirt." James Slattin Martin, Jr., had the bearing and appearance of a military man. His closely cropped iron gray hair added to the image and encouraged nicknames like the "Paratroop Colonel" and the "Prussian General." Many members of the Viking team would attest publicly that he had run a tight project, but even those who had cursed him under their breath over the years had to admit that the incredible performance of the spacecraft during its 11 -month cruise toward Mars and the normal postseparation checkout of [xii] the lander indicated that all the discipline and hard work Martin had put them through had been worth it. With a billion dollars invested in two spacecraft, someone had to have a firm grip. As the lander in its protective aeroshell fell freely toward the surface thousands of kilometers below it, Jim Martin listened to the controllers reporting tersely and calmly on the latest electronic news. ²

At 3 a.m., Albert R. Hibbs, a senior advanced missions planner at JPL, relieved George Sands in the commentator's booth. Hibbs, a veteran "voice" of many earlier unmanned spacecraft directed from Pasadena, had what one observer called "marvelous sense of theater." Smiling, Hibbs noted that the deorbit burn of the lander's eight small rocket motors had gone smoothly and the spacecraft had proper velocity. Impishly, he noted that it was also going the right direction.

At 2 p.m., everyone was still waiting. Hibbs reported: "So far, everything that is supposed to have happened ....has happened and right on schedule. We are rapidly approaching the surface of Mars...." As the craft followed its curved trajectory, Hibbs noted that it had only 11 340 kilometers to go.^*

4:43:08 a.m. PDT. Less than 10 minutes to touchdown, 28 minutes to confirmation. Al Hibbs informed his audience that he and George Sands would talk the lander down, but neither they nor anyone else at the mission center had any control over the spacecraft at this point; they could only keep listeners posted on the latest news. Obeying only its preprogrammed onboard computers, the lander was "inexorably going to the surface...." By now "the lander has felt the impact of the Martian atmosphere, although we won't know for 19 minutes."

4:53:14 a.m. PDT. Hibbs reminded the people at JPL that "Viking should be on the surface by now, one way or another." A steady volume of 18-minute-old data kept flowing into the control center. The Viking team....




Viking Project Manager James S. Martin, Jr., works at his desk at Jet Propulsion Laboratory.



[xiii]....watched each new data point with increasing interest. The flight path analysis group had devised a visual display that portrayed the predicted descent curve for the lander-a single line graph that measured the lander's altitude against time. That line, a gentle curve sweeping downward from left to right, ended at touchdown. Once the lander in its aeroshell reached about 244 000 meters, the upper limits of the Martian atmosphere, onlookers could watch on the TV monitors as the actual path of the lander (in the form of data points) was plotted against the predicted normal curve. That graph was the tangible link between the watchers gathered in Pasadena and the Viking spacecraft approaching Mars. The first data point was right on the "nominal" curve.

From mission control, a disembodied voice began calling out the velocity and altitude of the spacecraft. The descent progressed rapidly. At 98 707 meters, the spacecraft was traveling 4718 meters per second.

When Viking I reached 60 960 meters, Hibbs suggested, "....we can now put out some of the instruments that cannot stand the temperature of entry-pressure and temperature sensors that have to stick out of the aeroshell. " Calling attention to a second graph on the television screens, he said that the viewers could watch the gravity forces "build up on that graph. Very violent changes in the effective combination of Mars' gravity and atmosphere on the spacecraft." In just the few seconds that it had taken him to make that remark, the acceleration force had increased from 2.7 times to 5 times the normal Martian gravity. By the time the spacecraft reached 30,000 meters, the atmosphere was beginning to exert a braking effect, slowing the lander to only 3000 meters per second. The gravity forces continued to rise-6.8, then 8.4, the maximum force encountered. At 27 000 meters, the velocity dropped to 1820 meters per second. As the craft passed the 24 000 meter mark, Hibbs reported: "Well, we're coming down. We're coming down. It's a long period of glide; almost flat glide to get rid of some more of the speed before the parachute comes out." From mission control, the callout of the descent continued in a measured, emotionless tone. When the craft passed through an altitude of 22 800 meters, it was moving at 982 meters per second. The acceleration forces had been reduced to 0.8. At 5:09:50 a.m., the parachute deployed, slowing the craft even further, to 709 meters per second.

5:11:27 p.m. PDT. 1463 meters, 54 meters per second. At 1400 meters, the terminal descent engines started. At 5:12:07.1 a.m. PDT July 20, a voice in mission control called out, "Touchdown, we have touchdown!" A chorus of cheers rose for the even t completed 19 minutes earlier on Mars. "We have several indications of touchdown. " Mars local time was 4:13:12 p.m. when Viking I landed on the surface.

Jim Martin, who had been watching the descent curve on his monitor, stood up abruptly. He shook hands with William H. Pickering, former director of JPL, and exchanged congratulations with his teammates who [xiv] rushed in to his office. But then he paused for a moment to take another look at the televised data, wanting to be very sure that it had actually happened. A critical event in the life of the Viking project had come to a successful conclusion. Controllers and support personnel who had been quietly doing their tasks let loose with a burst of backslapping, embracing, and handshaking. In the auditorium, a newly opened bottle of cold duck was passed around as NASA public affairs officers and news people shared ceremonial sips. Viking 1 was safely down on Mars. ³

Nick Panagakos' public affairs officer from NASA Headquarters who had for weeks been answering questions for the press, smiled and shook his head. Like many of his colleagues, he had been telling people that Viking would land safely. But now that it had actually happened, he found it hard to believe. As the team in the control room settled back down to prepare for the reception of the first pictures of the Martian landscape, many persons around the Jet Propulsion Laboratory reflected on Viking's amazing odyssey.

* * *

When NASA planetary investigators began planning the exploration of Earth's closest neighbor, basic elements in their strategy were dictated by common sense. The space agency planners proposed to visit the nearest bodies first-the moon, Mars, and Venus. They planned to conduct simple projects initially and progress to more complex ones. Flyby spacecraft would be sent to take photographs and measurements and, after such basic reconnaissance had been made, heavier and more sophisticated orbiting craft would be sent to the target of investigation. After more detailed evaluations of the environment had been completed, atmospheric probes- either hard-landers (spacecraft that would crash-land) or soft-landers- would be used for further study. Different bodies would require different instrumentation. Photography, for instance, would not be suitable for cloud-covered Venus; on Mars it would be an experiment with exciting potential. During the past two decades, this strategy-flyby, orbiter, lander-has become a formalized part of NASA's planetary exploration program.

Mars, because it is reasonably close to Earth, has been the subject of much scientific examination. The Viking project was begun by NASA in the winter of 1968 to make landed scientific investigation of biological, physical, and related phenomena in the atmosphere and on the surface of Mars. The desire to explore for possible life forms on the Red Planet was one of the earliest goals of scientists who became part of the United States space science program, stretching Viking's roots back to the early 1960s. While NASA's first attempts to land craft on Mars were successful, that success did not come without a struggle. Chapter 1 examines the reasons [xv] scientists wished to have a closeup look at Mars and describes the new opportunities that opened with the coming of space travel. As Chapter 2 indicates, the dream was not transformed into reality until new and reliable launch vehicles became available in the mid-1960s, but the scientific community began early to prepare for landed investigations of the planet. Modest flyby probes such as Mariner it, using less powerful rockets than the later Viking's, provided new if discouraging information about Mars. Despite initial photographic evidence that did not encourage the search for life, a small group of biological scientists-who called themselves exobiologists-began to develop instrumentation that would serve as the prototypes for life detectors on spacecraft that might fly in the future. These activities are related in Chapter 3, while Chapter 4 deals with the plans for NASA's first Mars lander project. Called Voyager ^** and conducted by the Jet Propulsion Laboratory, this project was ambitious, perhaps too ambitious for the times. Expansion of the war in Vietnam and demands for federal funds for many sectors of the American economy began a period of budget problems for ISTASA. Voyager died for a complex series of reasons in late summer 1967.

While budgetary stringencies were to remain with NASA planners from that time on, enthusiasm for a Mars lander project also continued. The focus of that spirit shifted from JPL to the Langley Research Center. The aggressive team at the Virginia center entered the Mars game just in time to see Voyager terminated. Chapter 5 chronicles the Langley entry into the planetary spacecraft business. Chapter 6 tells the story of the Viking orbiter within the context of advanced Mariner Mars spacecraft. Jim Martin and his colleagues, realizing that the JPL people had mastered the flyby and orbiter trade, persuaded them to become part of the Viking team. As Chapter 7 indicates, the Viking lander demanded many new inventions. In addition to new and complicated mechanical systems, it also required closely knit managerial, technical, and scientific teams that could come together in a cohesive organization during the data-gathering and analysis phases of the mission.

Before collection of scientific information could begin, landing sites for the craft had to be chosen. Data obtained from the 1971 Mariner orbiter assisted the specialists in this task but, as Chapter 8 recounts, there was considerable debate over the best places to land, given both scientific interests and engineering constraints. Despite the time and energy given to site selection, Mars held some surprises for the Viking team. The first orbiter photographs, which the team hoped would certify the suitability of the preselected landing sites, showed extremely hazardous terrain. Site certification, described in Chapter 9, became a renewed search for suitable and safe areas on Mars. For nearly a month, the project members labored to find [xvi] a safe haven for the lander. Finding a site for the second lander was an equally time-consuming job.

In Viking, NASA's most complex unmanned space project to that date were many stories of great human effort and some of personal sacrifice. But the scientific results were the payoff. To have proved the technological capability to design, build, navigate, and land a spacecraft on Mars was not enough. Chapters 10 and 11 outline the scientific results of the Viking investigations and examine some of the unresolved questions. As so often is true in new fields of inquiry, as many questions were raised as were answered. And as earlier investigations of Mars have shown, the latest hypothesis can be upset by later, more detailed data. The Epilogue, therefore, considers possible future explorations of the Red Planet within the context of NASA's goals and other national priorities. One adventure was completed, but the exploration had just begun.

This book is just one of many possible histories that could be written about the events surrounding the Viking project. It is the official history because it was commissioned and paid for by the National Aeronautics and Space Administration. The authors began work shortly before Viking was scheduled to land on 4 July 1976, and they were present in Pasadena while Jim Martin and his team searched for a landing site. Exposure to the site selection process allowed us to see key project personnel at work and begin to understand the many complexities of Viking. We decided very quickly that we could not tell all the stories that participants might like to have told. We also concluded that, to appreciate fully the accomplishments of the project, readers should be exposed to the Mariner flights to Mars and to other planned but unconsummated missions to send landers to another planet. Thus our book evolved. In ignoring certain aspects or in describing others only briefly, we have not intended to slight other important aspects of the Viking effort. There are just too many stories and too many participants for them all to be included in this single volume.

* Hibbs and most of his Viking teammates used the common English measurements (miles and feet), but the authors have used metric units in this book to conform with NASA requirements that the systeme international d'unites (SI) be used in all NASA publicationbs.

** NASA used the name "Voyager" again later for another planetary program, in which two spacecraft investigated Jupiter in 1979 flybys.