In mid-November 1973, Pioneer 10 crossed Jupiter's bow shock, the invisible zone in which the onrushing solar wind is deflected away from the planet by its magnetosphere. Now tension and excitement mounted in equal proportion, as the radiation levels rose and the scientific bounty inundated the jubilant PIs. "Every hour we found something new," says Van Allen. "It was a period of intense discovery." Pioneer mapped Jupiter's magnetic field, measured its mass and temperature, probed its atmosphere, analyzed its radiation--and took the first pictures of Jupiter from outside Earth's atmosphere.
Because Pioneer's weak signal dictated a slow data rate, the images trickled in painfully at only 1024 bits per second. But any pictures were a bonus, because Pioneer didn't even have an actual camera--its constant spinning motion made such a luxury useless. Instead, an imaging photopolarimeter (IPP), a phototube device for measuring light intensity and wavelength, swept a small narrow-angle telescope across the planet in sequential strips as Pioneer rotated. Earthbound computers constructed images in true color from the IPP's red and blue light scans. A Pioneer Imaging Control System (PICS), developed by the University of Arizona, provided real-time video images for the press and television networks. Although hardly the gorgeously-resolved marvels which Voyager would later provide, the pictures awed both the public and the scientific world, and even won Ames an Emmy Award.
As periapsis, the point of Pioneer 10's closest approach to Jupiter, drew near, the control center at Ames flooded with scientists, technicians, engineers, and NASA officials. TRW personnel were also on hand, even though O'Brien says that "once we launched the spacecraft, we had no further contractual responsibility." But the urge to watch their baby confront its ultimate challenge was too much to resist.
With Pioneer 10 at its destination, sleep was a rare commodity and black coffee a staple of life. For those at mission control, a planetary encounter is a blur of long hours of waiting, brief flares of excitement, hurried meals, intensive discussions, daily press briefings and constant meetings. On Pioneer, a particularly infamous Charlie Hall management technique was the "stand-up meeting." Van Allen wryly recalls, "He was famous for the idea that the way to have a brisk, get-to-the-point meeting was not to let anyone sit down." Every morning--standing up-- Hall, the PIs and the operations staff exchanged five-minute reports on activities, discoveries, or problems of the past twenty-four hours, and planned the day to come.
Pioneer was fast approaching its moment of truth in Jupiter's radiation field. "All of us were finding an enormous intensity of radiation, and the question was whether the spacecraft was really going to survive the closest approach or not, whether some systems would be knocked down," says Van Allen.
Shortly before 6:30 PM Pacific time on December 3, 1973, Pioneer 10 passed only 81,000 miles above the clouds of Jupiter, battered by radiation, some instruments saturated beyond their limits to register--but still alive and functioning. Van Allen adds, "We passed through periapsis and kept on going and the intensity started going down. We were all cheering that the little spacecraft had made it."
The suspense wasn't over, though. Pioneer now began to swing around the far side of Jupiter, where it would be on its own, out of communication with home. Although speeding away from the planet, the craft wasn't yet out of the woods, still deep within the radiation belt. "Everybody was scared and praying it would be alive when it emerged," says O'Brien.
A tense hour of standing around, chewing nails and pencils, and gulping of the always-present coffee ensued as everyone waited for Pioneer to call Earth. Few groups of human beings are as anxious or as helpless as a team of scientists, engineers and flight controllers waiting to hear from an out-of-touch spacecraft. Some resort to gambling. O'Brien admits, "I made a bet with one of our scientists that we would survive the radiation belt of Jupiter and he bet we wouldn't."
Slowly, as the time for signal reacquisition arrived, an image began to appear, pixel by pixel, on the PICS at Ames. The Pioneer team watched a bright line slowly becoming a crescent on their screens. They were seeing something no one had ever witnessed before: sunrise on Jupiter, as the IPP looked back toward the planet.
Hall, O'Brien, and the rest of the Pioneer team had won their bets. Pioneer 10 accomplished its last major objective by using Jupiter's gravity and orbital momentum to hurl itself out of the solar system toward interstellar space at 25,000 miles per hour, proving the feasibility of the gravity-boost technique for later missions to Saturn and beyond. O'Brien later collected his prize: an order of Beefeater stew.
As the PIs began the years-long task of sifting through and analyzing the vast treasure trove of new information, controllers retargeted Pioneer 11 on a different trajectory to fill in the scientific blanks left by its older sister at Jupiter, and later used Jupiter's gravity assist to send Pioneer 11 on to the first Saturn encounter in 1979. All considered the project a complete and unadulterated success, but thought that the story of Pioneer 10 was essentially over.
They were only half right. The Pioneer Jupiter mission was
definitely a historic triumph of science and engineering, but the
spacecraft refused to go gentle into the night of interstellar
space. Pioneer 10 still had a few more surprises to spring.
"It's a lot of incentive to work on something that man has never done before," Charlie Hall observed in 1999. But is that enough to explain the way Pioneer 10 has defied all the odds to survive two decades longer than its creators expected? Is it just pure luck, or could its success be repeated today?
With Hall's emphasis on keeping hardware simple and mission objectives sharply defined, the Pioneer project is a paragon of how NASA's "faster, better, cheaper" philosophy could be achieved. Even thirty years later, it's a superb demonstration of strong and responsive project management, constant communication among the engineers designing the spacecraft and the scientists conceiving the mission, accountability at all levels, and the conscientious dedication of the prime contractor. Recalling his Pioneer experiences, John Simpson says "we were in this mode of faster, better, cheaper" long before it became NASA's guiding mantra in the 1990s. James Van Allen agrees. "As far as I'm concerned, NASA just rediscovered the principle," he says ruefully.
TRW's Bernard O'Brien tends to be slightly dubious about the "faster, better, cheaper" notion. "My personal opinion is that you can do any two of those and not get into too much trouble. Doing all three is a real challenge." Despite "a few cost problems" on Pioneer, he says, "to have done what we did significantly cheaper would have been almost impossible." Yet at about 100 million dollars total cost, Pioneer was hardly the billion-dollar extravaganza of the more sophisticated missions that followed.
Pioneer's veterans consistently stress the probe's straightforward design. "It was part of the philosophy to keep the spacecraft simple and uncomplicated by a lot of electronic wizardry," says Dave Lozier. The spin-stabilized configuration, use of spaceflight-proven systems, redundancy of vital components, and the navigation and communications techniques which allowed ground-based piloting all reduced the risks of irreparable on- board breakdowns or malfunctions. Hall explained that aside from the RTGs and some of the science instruments, "the rest of the spacecraft was pretty much standard-type electronics."
O'Brien also cites the project's emphasis on reliability, which involved exhaustive testing of parts and systems before Pioneer ever left the ground. At TRW, he says, "we spent a lot of time, money and effort on making damn sure those parts were designed, built and tested before we ever brought them into our house from the vendors." The PIs who designed and built Pioneer's science packages followed the same philosophy. John Simpson's Charged Particle Experiment was the first scientific instrument repairable in space. "It could send the message 'I'm sick, I've lost this detector,' and we had in our computer all the options to make the correction by switching amplifiers, and we could send a signal to fix it," says Simpson.
But simple, reliable design is only part of the picture. No matter how impressively engineered, Pioneer 10 could never have done its job without exceptional project personnel under outstanding leadership. Talk to any of the Pioneer team, and it won't be long before Charlie Hall's name is mentioned--and always with an uncommon fondness, respect and even awe. "Charlie Hall was really a star," says Van Allen. "He was one of the most intelligent and responsive project managers I've ever worked with in the NASA system. He managed the whole thing with a firm hand but was very constructive and receptive to all the crazy requirements we tried to meet. He was outstanding, no doubt about it."
The feelings were mutual. "Pioneer was blessed by so many good people working on it, from the scientists to the lowest technician," Hall remembered. "I used to sit there and watch the scientists and think, 'God, what a team we've got.'"
Charlie Hall passed away in August 1999. He left behind a legion of friends and colleagues who remember him warmly for his "intelligence, persistence and leadership throughout his career," as NASA administrator Dan Goldin phrased it in a memorial service.
And of course, he left behind the remarkable Pioneer
spacecraft. Perhaps no other human being has such a unique
legacy--a legacy which might be almost forgotten by now, if not
for the dogged efforts of the people Hall inspired and led.
"It's been a real struggle," James Van Allen says. "I was one of those who gave a eulogy at NASA headquarters on the achievements of Pioneer, and meanwhile I was working the hallways trying to keep it going."
At first it wasn't so much of a problem. With the spacecraft still functioning well after its Jupiter flyby and headed for unexplored space, NASA extended its mission to find the heliopause, the boundary marking the end of the sun's sphere of influence. Most scientists had speculated that the heliopause ended around the orbit of Jupiter, but when Pioneer 10 became the first spacecraft to cross the orbit of Pluto in 1990, it still hadn't found it. Neither had Pioneer 11 by the time its problematic RTGs finally gave out and the craft ran out of power in 1995.
Pioneer 10 soldiered on, despite all predictions that it would soon suffer a similar fate. As other important missions demanded Deep Space Network resources, reducing the time that could be spent tracking Pioneer, NASA support and finances dwindled. Hall's successors cast about tirelessly for ways to justify keeping the project alive. Valuable research still being done on Pioneer data by Simpson and Van Allen helped for a while, but pure science work on particles and fields lacks the public glamour and pretty pictures of spectacular planetary flybys.
NASA headquarters finally pulled the plug on Pioneer 10 in 1997. The spacecraft was still loyally transmitting its data, but aside from the Pioneer team, no one seemed to care anymore.
But if a scientific reason wasn't enough to keep the project alive, Larry Lasher managed to find a technical one. When Ames was named as lead center for the Lunar Prospector project, Lasher convinced NASA that tracking Pioneer 10 would be a perfect training exercise for Prospector's controllers, buying Pioneer a couple more years of life.
After Lunar Prospector was purposely crashed into the moon in 1999, prospects for Pioneer 10 again looked bleak. But the Pioneer diehards were used to that by now. And for once, they got lucky: "A white knight came along in the form of a NASA headquarters study on weak signals," Lasher explains. With more deep space missions in the pipeline, NASA is developing new techniques of extracting useful telemetry from very faint signals --such as Pioneer 10's distant chirp. For a few more years at least, Lasher has the blessing of headquarters to maintain Pioneer's link with home.
Ironically, now that its political problems have receded, it's pure physics that threatens to close the books on Pioneer.
Technological progress long ago caught up with Pioneer and left it in the dust. Designed to operate in an age of huge mainframe computers and punchcards, Pioneer 10 can't be controlled with today's superfast desktop computers. The project's remaining original DEC PDP 11-14 computer, standing like a museum piece in the Pioneer control room at Ames, must be kept operating in order to transmit navigation commands. Pioneer operations supervisor Ric Campo laments, "The equipment is barely keeping alive. Much of the hardware is maintained by stripping cards and interfaces from similar hardware in the Pioneer control center." Although the data telemetry system was reconfigured several years ago to run on a Macintosh rather than the old mainframe, such a fix isn't possible for the command system. Present-day engineers can still interpret the data sent by Pioneer's ancient systems, but the reverse isn't true: Pioneer can't understand commands not compiled by the computers of its own age.
Another rapidly-approaching problem is an impending change in the Deep Space Network's system software. Lasher explains, "We're an old project and we have a specific software arrangement that they use to contact our spacecraft, and they're changing it over in 2001 or 2002. Even if we wanted to, we couldn't be supported because the DSN software wouldn't be able to track it any longer. So we have until about 2002 for a hard cutoff."
To conserve power, most of Pioneer's science instruments have been turned off. Only Van Allen's Geiger Tube Telescope is still operating--and still looking for the heliopause. It's a scientific horse race to see whether Pioneer 10 will be able to make its final discovery and send the news back home--or whether contact will be lost first.
Nearly seven billion miles from Earth, Pioneer 10's voice is barely strong enough to be heard and is fast approaching the sensitivity threshold of the DSN. "It's hanging on by a thread," says Lasher. "The signal's getting weaker and weaker, and I would guess it isn't going to last that long.
"But I could be wrong," he adds, with guarded optimism. "It's happened before."
Inevitably, Pioneer 10 will pass beyond the reach of the huge dishes of the Deep Space Network, and Earth will hear no more from the plucky craft. But in the final analysis, maybe it doesn't matter. Transmitting or not, Pioneer 10 will outlive all of us, and quite probably Earth itself.
One day, about five billion years from now, our sun will
expand into a red giant star, consuming the Earth--and humanity
itself, if we haven't moved elsewhere by then. But something of
Earth will yet survive. Pioneer bears a gold-anodized aluminum
plaque, designed by Carl Sagan and Frank Drake to describe the
craft's origins and its makers to any extraterrestrials who may
someday intercept it. Long after its planet of origin is dust,
Pioneer 10 will still be cruising through the galaxy as our
eternal emissary, telling the universe that we were here.
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(C) 2000-2001 Mark Wolverton. All rights reserved.
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