Category Dreams, Technology, and Scientific Discovery

An elaborate series of environmental tests were performed on all payload compo­nents, subassemblies, and the fully assembled payloads. The environmental testing philosophy included two types of test: (1) type approval testing of an engineering model payload and (2) flight acceptance testing of all flight models.

The primary purpose of the type approval tests was to assure that the basic designs were adequate to withstand the rigors of launch and the in-orbit environment. Those

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test levels were substantially higher than actually expected, to provide a margin of safety.

Flight acceptance testing was designed primarily to weed out errors in construction and early parts failures. Care was taken not to exceed the expected launch levels to avoid fatiguing any of the flight components.

Without going into the many details of test configurations and levels, the battery of environmental tests included (1) shock, (2) acceleration, (3) spin, (4) temperature (static, cycling, and long-duration), (5) combined temperature and vacuum, and (6) vibration.

A failure of the Engineering Model cosmic ray package during its type approval testing on 7 January caused considerable alarm. During the second vibration test, the GM counter rate was seen to be somewhat low. Upon closer examination, it was found that the ceramic insulator supporting the central wire in the counter had cracked within its encapsulation—a recurrence of another of the problems encountered earlier during testing of the Vanguard prototype instrument.

It was too late to change the design without delaying the Explorer I launch. Since the flight payloads had satisfactorily passed the lower-level flight acceptance tests, it was decided, with great trepidation, to proceed without modifying them. Luckily, the final flight instrument survived its launch, and the instrument operated perfectly in orbit.

The entire suite of tests ended with a measurement of the overall temperature characteristics of each completely assembled flight payload. They were placed in a temperature chamber and operated solely from their internal batteries. The GM coun­ters were illuminated by a standard Co60 radioactive source. The resulting counting rates became the standard for operational checks made on the payloads at the launch site.

At the end of all Deal I flight payload testing, I calculated that the overall variation of GM counting rate with temperature would be in the neighborhood of 5 percent over the temperature range 0 degrees to 50 degrees centigrade. Although it would have been better to relocate an internal temperature sensor closer to the GM counter to facilitate more accurate correction of that temperature effect, it was too late to do so for Deal I. However, that was done for Deal II.30

All in-flight payload temperature data were tabulated at JPL and were used in correcting the GM counter flight data at Iowa.31

The Deal I satellite bore no resemblance to the Vanguard configuration. It was, however, similar to the configuration that we had worked out at Huntsville during the preceding summer, as can be seen by comparing Figures 7.1 and 8.4.

The first Deal I flight payload was completely assembled, tested, and weighed by 11 January. Its total weight, not including the Rokide thermal control coating on the shell and the fourth-stage rocket motor, was 18.51 pounds (some records list

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MICROMETEORITE GRIDS

FIGURE 8.4 The Explorer I satellite, including the final rocket stage below the central high – power antenna gap. The shell ofthetop instrument package is cut awayto showthe arrangement ofthe inside components.

18.13 pounds). By that time, the booster rocket and upper stages had been completed at ABMA and JPL and transported to the Cape. On 17 January, the Redstone booster was hoisted to a vertical position on Launch Pad 26A. Installation of the upper-stage rocket clusters followed, as the Jupiter C took shape.

In addition to an engineering development model, three flight payloads were assem­bled for the Deal I launch. Figure 8.5 shows one of them. The payload designations, the GM counters used on each, and their ultimate dispositions, as far as they are known, are tabulated in Table 8.1. The GM counter numbers are listed because they are the only identification durably impressed within the entire instrument packages, and therefore the only numbers that can be used to positively identify surviving pay­loads. The numbers are very faintly stamped on the GM counter stainless steel shells just above their threaded mounting flanges.

The space museum at JPL possesses a full-scale model of Explorer I, plus a cutaway version of the instrument. The cutaway instrument includes a cosmic ray counter and its electronics. As it is believed that only four of the complete Deal I packages were built, it is possible that this unit is the engineering model.

Additional models have been displayed from time to time. Those models are likely either prototype units prepared within JPL before the official decision to proceed with the Deal program, and therefore lacking the scientific instruments, or else spare parts

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that appear authentic only when viewed from the outside, namely, antenna insulators,

shells, and cones.

Figure 11.3 illustrates, in a greatly simplified form, the path by which the low-power data from Explorers I and III and the high-power data from Explorer I passed from the sensors in space to produce human-readable tables and graphs in our Iowa laboratory. The Explorer III high-power data were handled quite differently, as described later.

Pulse rates registered by the GM counter and the micrometeorite impact micro­phone were scaled on the satellite, that is, reduced by factors of 32 and 4, respectively, to produce more manageable rates for telemetry. The sensor signals modulated the frequencies of audio oscillators, and the tones were combined to form composite signals, which, in turn, modulated the satellite transmitters.

At the ground receiving stations, the receiver outputs were recorded on magnetic tapes, and the tapes were shipped to JPL. There the data were examined to ascertain their quality, and the satellite temperatures were computed. Initially, magnetic-tape copies of appropriate data channels were sent to SUI and the Air Force Cambridge Research Center (AFCRC). Somewhat later, the original tapes were sent to Iowa.

In our laboratory, the tapes were played back and the signals were passed through a bank of filters that separated the four original audio tones. The filters were followed by discriminators that converted the audio tones to the relatively slowly varying signals like those that had originated in the satellite. Thus, the outputs of the four

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discriminators were identical with the inputs to the satellite multiplexer (except for the addition of noise). Those four signals drove moving-pen galvanometers to produce ink traces on continuously moving paper strip-charts.

here was no time for relaxation following the Explorer III launch. Even before the public announcement of the discovery of the high-intensity radiation on 1 May 1958, immense pressure was building in the United States for follow-on missions to address the questions posed by the data from the first two successful Explorers.

The Army group at Huntsville was already working on a next logical step—the substitution of the Jupiter missile for the Redstone as the first stage. The larger booster would be topped by the same cluster of solid fuel upper stages as employed in the Jupiter C-Juno I configuration. They dubbed the enhanced vehicle Juno II, and work quickly began at Huntsville on designing a satellite for that launcher. That satellite was referred to as the IGY Heavy Payload initially, and, after NASA was formed in October 1958, it was given the prelaunch designation Payload 16 (PL-16). When its second launch attempt was successful in October 1959, it became Explorer 7.

However, work on that satellite was interrupted by another new project, Argos and Explorers IV and V

y studies in physics and engineering at the Iowa university, the work in the Physics Department’s Cosmic Ray Laboratory, and our family life were inextri­cably intertwined and all-consuming throughout the seven and a half years that I was there. That was the most exciting period of my life and had more to do with shaping my professional future and person than anything else that happened during my entire life.

Family life

When I entered the university in early 1953, Rosalie and I began our new experience with daughter Barbara, who was approaching her first birthday. Sharon was born in June 1953, at the end of my first semester of study. Son George came along just eight days before the Explorer III launch, and daughter Kathy arrived just as I was receiving my Ph. D. diploma.

For the initial months, we managed the Ludwigheim family farm near Tiffin while Dad and Mom were in Des Moines for his participation in that year’s session of the state legislature. I commuted the eight miles to the campus. When my parents returned in the early summer, Rosalie and I moved our growing family into Finkbine Park.

That home for four years contained a very small living room, a miniscule kitchen with a small table for dining and homework, a bathroom with a minimal shower stall, two small bedrooms with diminutive closets, a rather large storage closet for all the things we could not cram into the living spaces, and a single oil-fired space heater in the living room.

In spite of the rather austere living conditions, life there was, overall, enjoyable. Our neighbors were also struggling students, most with children who were about the

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same age as ours. We sometimes referred to our little enclave as “rabbit village.” Our common financial and living conditions, plus our shared common purpose, resulted in a strong bonding and sense of community. We count some of our neighbors there among our closest friends yet today, even though their interests and training were in completely different fields and they took up postgraduation work in all parts of the country.

Our initial rent of $35 per month included electricity, oil for the space heater, and gas for the kitchen range and water heater. By the time I ended my undergraduate work in 1956, the monthly rent had ballooned to $50.

One year into my graduate work, in the summer of 1957, I signed up for only a three hour research load to allow more time for my satellite design work. The light summer academic load meant that I was no longer qualified for married student housing, so we rented a small two-bedroom house on Rochester Avenue near Iowa City’s eastern edge. It had a small combined living and dining room into which our 9 by 12 foot rug exactly fit. Fortunately, the house had an unfinished full basement. Although initially unsuitable for other than our washer and dryer, it had great potential. Its walls and ceiling were still covered with a thick layer of grime from the days when the coal bin was in active use. I hosed off the worst of it, rented a paint sprayer, and encapsulated the walls and ceiling with a thick coating of paint. I also rewired the basement to make it safer. A study area was delineated by a bed sheet hanging from one of the open joists. With a desk fashioned from a hollow-core door and set of wrought-iron legs, I had a comfortable place for study somewhat removed from the noise and confusion of the family and our tight living quarters upstairs. Our initial monthly rent there was $65, seemingly a princely sum at the time.

Rosalie worked just as hard as I did during our university years. Obviously, she carried the major responsibility for our household. In addition, she worked as a nurse’s aide at the University Hospital for a two year period. While she worked the night shift during the first of those years, she would come home after work to prepare breakfast, take care of the children during the morning, and feed them lunch. Then, when she put them down for their naps, she would get a short rest. After the children woke, she took them to our neighbor Charlotte Boley, who watched them until suppertime approached. Then Rosalie would collect the children and prepare supper. During most of that year, she felt that she was floating in a daze.

That regimen was too hard for her to sustain, so she moved to a shorter 7:00-11:00 PM evening shift during her second year there. During that era, she prepared the children for bed before leaving for work, and I watched them and put them to bed while I studied until her return.

Near the end of our university epoch, Rosalie worked for about two years at the First Presbyterian Church, where we were members. On five evenings each week,

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she oversaw the youth lounge, where students gathered from the nearby campus. On Sundays, she fixed evening meals for them.

We had one extended break from the campus routine during my student years, when we spent the summer of 1954 with Rosalie’s parents in Corvallis, Oregon. Her father managed radio station KRUL at that time, and he offered me a position as chief engineer for the summer. The FCC First Class Radio Telephone Operator’s License that I had earned just before leaving the Air Force qualified me for the position. When we arrived in Corvallis, I discovered to my surprise that the position also entailed working a shift as radio announcer—an interesting situation. My voice was well suited to radio, but I knew that, being a relatively nonverbal introvert, I lacked the proclivity for extended extemporaneous chatter needed by a radio personality. That had been borne out by my experience with amateur radio, where I enjoyed building the equipment but disliked rambling on the air about nothing in particular. At the radio station, I dreaded the on-air unscripted tasks such as conducting chat shows.

As mentioned earlier, we did take shorter family vacations from time to time. With everyone in the family enthusiastically embracing tent camping, most of those vacations involved trips by car to various locations, with camping along the way and in the parks that we visited. Those gave us complete breaks from our normal daily lives at a cost that we could afford.

Rosalie and I carefully protected certain family activities. With few exceptions, break­fast and the evening meal (supper in midwestern rural parlance) were carefully guarded family affairs at the dining table. A review of my notebooks and journals confirms that Sundays were nearly always preserved for church and family. That included many Sunday afternoons with my parents and other family members at Ludwigheim. On other Sundays, we went on drives, visited a nearby park for a picnic, or engaged in some other family activity.

In retrospect, my family did not receive as much of my day-to-day attention as might have benefited all of us. Overall, however, the children received good guidance and loving care and developed a strong sense of responsible behavior. Interestingly, none of them followed my lead into the physical sciences. Rosalie, who eventually realized her lifetime goal to become a registered nurse, appears to have had a greater influence in setting their life’s directions. Two of our children became nurses, one a medical doctor, and one a Ph. D. animal virologist.

y the fall of 1952, all of the essential elements were in place at the Iowa Physics Department for a sustained program of upper atmospheric research. There was outstanding leadership, a capable staff, a cadre of eager students, appropriate tools and techniques, experience with field operations, and modest funding. Early scientific re­sults were appearing in print. James Van Allen and his new group were already solidly established in the national and international science arena as leading contributors to cosmic ray research.

Entering opportunity’s door

Purely by chance, I arrived on the scene at about that time. When my tour of active duty with the Air Force ended on 18 December 1952, I returned to my Iowa family home near the tiny town of Tiffin, located just eight miles west of Iowa City. My single-minded goal was to enter the University of Iowa to study physics. With no understanding of the significance of the situation that was developing at the time, a tremendous opportunity was opening.

For a number of years my father, George M. (GM) Ludwig, conducted a daily morning program over local radio station KXIC from his Ludwigheim farm home. He had interviewed Van Allen, Meredith, and Blodgett in October upon their return from the summer’s rockoon expedition. Van Allen and Meredith returned for a follow-up interview a few days after I arrived home. In the course of that morning’s discussions, Dad (acting as my self-appointed agent) turned to Van Allen and asked, “George is just back from the Air Force and is looking for a job. Might you have something for him?” Van Allen replied that he might and suggested that I come to his office the following Monday to pursue the question further. I did so, and he offered me part-time

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work as a research aide in his Cosmic Ray Laboratory, at 75 cents per hour. I eagerly accepted his offer, began work immediately, and was well established there when the spring semester opened in February 1953.

Anderson’s 1957 Fort Churchill expedition As Kinsey Anderson was arriving in Iowa City in September 1955, our summer rockoon expedition was returning with new information about the auroral soft radiation. When Kinsey saw those results, he noted that the anomalous radiation was occasionally penetrating to altitudes lower than the rockets’ peak altitudes. In fact, the auroral soft radiation was sometimes seen at altitudes that might be reachable directly by Skyhook balloons. He believed that balloon flights, flown for extended periods of 10 to 30 hours at their peak altitudes, might be able to capture synoptic and time variation information on both the auroral soft radiation and low-energy cosmic rays that was not obtainable from the relatively short duration rockoon flights.

Kinsey had been impressed by a seminar at Minnesota in late 1954, in which Phyllis Freier described a potential IGY project for studying cosmic ray variations. She suggested that a series of balloon launches covering an extended period carry a standard set of cosmic ray particle detectors to study those variations.

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Those two lines of thought converged, prompting Kinsey to submit a proposal to the U. S. National Committee for the IGY in November 1955. It called for a large number of high-altitude, long-duration balloon flights to be carried out during 1957 at Fort Churchill, Canada, a site well within the auroral oval.14

Kinsey immediately began designing an instrument to achieve that objective. It in­cluded three basic detectors: (1) a GM counter telescope, (2) a single GM counter, and (3) a scintillation detector using a thallium-activated sodium iodide crystal mounted on the front of a photomultiplier tube. The scintillation detector was configured to have high efficiency for X-ray radiation at energies above about 10 keV He expected the combination of instruments to reveal new information about the energy spectrum of the parent electrons that were responsible for the auroras.

However, Kinsey ran into serious problems in moving his project forward. To begin with, rules at the University of Iowa at that time did not permit junior researchers to submit proposals to outside agencies. Van Allen stepped in to sidestep that hurdle. The next step was to gain U. S. and IGY programmatic and financial support. In late 1955, Homer Newell’s Special Committee for the IGY (operating under the umbrella of the U. S. Upper Atmosphere Rocket Research Panel) reviewed his proposal and rejected it, apparently through some misunderstanding between Kinsey and the committee. Newell went so far as to declare that, beyond the funding issue, the U. S. military support group at Fort Churchill would not be permitted to support it.

Kinsey then attempted to obtain funding via the National Academy’s Technical Panel on Rocketry for the IGY. Scott E. Forbush, as its chairman, explained that nearly all of their funds for U. S. IGY cosmic ray research had already been committed. He asked if $15,000 would permit a useful program (compared with the $60,000 that Kinsey had requested). The panel also stated that, if approved, Kinsey would have to switch to a substantially different detector complement, to bring it more in line with programs at other locations that had already been approved. Specifically, it would have to include two instruments like those being used by the Minnesota group: a 10 inch diameter Neher-type integrating ionization chamber and their single GM counter design. Under those conditions, it would not be possible for Kinsey to in­clude the envisioned scintillation detector, and the nature of the project would be substantially different than originally envisioned.

Nevertheless, Kinsey quickly replied that he would be able to achieve meaningful results with that arrangement and submitted a revised proposal for the new instruments and a reduced number of flights. That resulted in approval for the modified program in April 1956.

Even then, the way was not clear. Newell had forbidden support by the U. S. military support at Fort Churchill, so other arrangements had to be made for launch­ing the balloons. Acting on Van Allen’s suggestion that he contact Donald C. Rose

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of the Canadian National Research Council, the problem was eventually resolved when Kinsey’s program was made part of the joint Canadian-U. S. IGY program, with Canada taking responsibility for the launches. Kinsey later reported that the arrangement with the Canadians turned out to be a very happy and productive one.

Developing the new instruments presented another major challenge to Kinsey, as he had no previous experience with ion chambers. With help from several students, and benefiting from the instrument shop’s much-earlier experience with Bob Ellis’ ion chambers (described in the first chapter), he prepared the instruments during 1956 and the first half of 1957. The spherical chambers had to be designed, manufac­tured, and assembled, and then they had to be baked out, evacuated, filled with argon gas, and calibrated (Figure 4.3). And the GM counters and various associated elec­tronics had to be designed and built. Completing the work was touch-and-go, and the last few ion chambers were completed only days before the first scheduled balloon launch.

With the various delays, final approval for the flights was not obtained until April 1957, only 10 weeks before the field operation was to begin. The schedule was met, however, and between 7 August and 7 September 1957, Kinsey, with help from three undergraduate students, directed the launch of 14 of his balloons from Fort Churchill. In total, they obtained about 175 hours of data from altitudes above 18 miles.

Kinsey related a fascinating tale about a highly improbable event that occurred during their field operation. In his words:

CHAPTER 4 • THE IGY PROGRAM AT IOWA

The program of IGY balloon launches in 1957 was punctuated by a remarkable coincidence in space, time, and people. After we had launched a balloon on 7 August, we hurriedly loaded the inflation gear into the panel truck and sped toward the main base and our telemetry station. The road closely paralleled the western shore of Hudson Bay. Glancing eastward over the Bay I saw a polyethylene research balloon coming out of a low-lying cloud layer. The balloon we had just launched had moved rapidly westward and away from Hudson Bay only a few minutes before. The intruder collapsed onto the rocky beach. We stopped the truck, started the Homelite generator, and snapped on our checkout telemetry receiver. We were indeed still receiving the VHF telemetry signal from our balloon off to the west. I then guessed that the interloper had to be a balloon used by the SUI group launching Rockoons in the Davis Strait half a continent away to the East. Running to the beach where the balloon lay partly in the water and partly on the beach, I chopped off the end portions with the hunting knife I carried (most persons engaged in launching large balloons carried such a knife believing it might save their life should they become fouled in a line as the balloon was released). When we returned to Iowa City, I showed the balloon ends to Laurence Cahill who verified they were from a balloon of the type used that summer for the Rockoon launches.15

Although most of Kinsey’s flights provided interesting and useful data, the one on 29 August 1957 was especially noteworthy. A Forbush decrease in cosmic ray intensity marking the beginning of a geomagnetic storm was detected by monitors at numerous ground locations while the balloon flight was in progress. The cosmic ray decrease at flight altitude was about twice as large as that observed on the ground. Although soft radiation (X-ray) was seen frequently throughout the flight, a strong burst of X-rays lasting about five minutes was seen in the balloon’s instrument at a time coinciding with the beginning of the storm. Ground observers reported that they had seen bright and active visible auroral during the period of observation. That was one of the earliest cases where the direct effect of energetic particles (electrons) was associated with such a geomagnetic phenomenon.

During flights on several other nights when quiet auroral arcs appeared in the sky, no similar X-rays were seen by the balloon instruments. This led to Kinsey’s inference that the quiet arc type of aurora did not involve electrons having energies high enough to produce X-rays that could penetrate that deeply into the atmosphere.16

Returning to Fort Churchill in 1958 Following up on his 1957 success, Kinsey proposed a series of balloon flights for August-September 1958 to further study the auroral zone radiation. Again, the balloons were to be launched from Fort Churchill. Approval was much more straightforward for that proposal—he submitted it to the U. S. National Committee for the IGY in October 1957, and it was approved relatively quickly.

Assisted by Donald Enemark, they made substantial improvements in the instru­ment design. They improved the low-temperature performance of transistor ampli­fying and scaling circuits, and the weight of the package was reduced by replacing the vacuum tube transmitter with one employing silicon transistors. In August, the

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two, joined by students Donald Stilwell and Louis Hinton, made their way to Fort Churchill with their instruments.

During the August-September 1958 period, they made 10 balloon flights, col­lecting 150 hours of high-altitude data. Kinsey’s account of the launch operations provides interesting reading.17 It tells of launches made during windy conditions from locations ranging from the leeward side of an aircraft hangar to the playground of the Fort Churchill elementary school, where many eager young faces watched from the windows. The flights produced varying results, with some indicating only quiet-time background cosmic radiation, while others showed moderate auroral X-ray activity.

The flight launched at about 8:30 local time the evening of 21 August was more exciting. By 10:30, the balloon had settled at its float altitude. Throughout the night, the counting rates were monotonously constant, revealing only the presence of the normal background cosmic rays. They were sufficiently uninteresting that Kinsey felt comfortable in catching a few hours’ sleep. After breakfast, he returned to the receiving station to find the situation unchanged. However, at about 9:45 on the morning of 22 August, things changed dramatically. The pen movements on the data recorder began to speed up—over several minutes, the rates climbed to previously unseen levels. All detectors were vigorously responding to some form of ionizing radiation. In Kinsey’s words:

I was especially struck by the rapid pulse rate of the usually sluggish ionization chamber.

Ionizing radiation was reaching the balloon at intensities far beyond anything that we had encountered on any previous flight. Recovering my composure, I began to think about what the detector responses were telling us. Careful study of the data received to that point convinced Donald Enemark and me that there were no instrument malfunctions. The ratio of the ion chamber to single counter response was much higher than could be produced by X-rays or gamma rays; therefore, the ionizing radiation could not be due to auroral associated X-rays.

The most powerful information for identifying the ionizing radiation came from the ion chamber-to-counter telescope ratio. That ratio told me the ionizing radiation could not be electrons, alpha particles, or heavier atomic nuclei. The measured ratio was just what I expected from fluxes of protons. After our return to Iowa City, I rechecked calibrations and made more detailed calculations and found the average energy of the protons arriving at our balloon over Fort Churchill, on 22 August 1958 to be 170 MeV.18

A highly varying pattern evolved over the next hours. The counting rates dropped and rose over a three hour period, and then the heavily ionizing radiation began a slow but steady decline. That continued throughout the rest of the morning and afternoon. Some protons were still present, however, when the transmission from the balloon ceased at about 5:00 in the afternoon of 22 August.

The team soon learned that an intense burst of radio noise was emitted from the Sun starting at about 8:15 AM, about 90 minutes before the protons were seen by the

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balloon instruments. They also learned that a great solar flare had been observed to begin about 75 minutes before the proton arrival.

That event did not produce a measurable effect in ground neutron monitors, as did some other rather rare superflares, like the one that occurred on 23 February 1956. It was clear that the proton energies were too low for either the primary or the secondary particles to penetrate the atmosphere and reach the ground.

From his flights and the work of others, it soon became understood that the Sun produces, in addition to the huge flares previously seen, more frequent smaller flares that emit large fluxes of protons of much lower energies than those produced by the large ones. This new knowledge played an important role in the evolution of the thinking about solar processes and solar-terrestrial relationships.

McDonald to Missouri and Minnesota On 27 June 1958, with help from aide Louis Hinton, Frank McDonald flew a two million cubic foot Skyhook balloon from Moberly, Missouri, to study latitude variations of the cosmic ray heavy nuclei and their relation to the sunspot cycle. The instruments were recovered the next day, and Frank and Louis flew immediately to International Falls in northern Minnesota to fly them again there. Those observations further extended the latitude range of Frank and Bill Webber’s earlier heavy-nuclei observations.

And Anderson back to Canada Kinsey Anderson’s final Iowa balloon-launching expedition was to Resolute, on Resolute Bay, Cornwallis Island, Canada. He chose that location because of its nearness to the Earth’s north magnetic dip pole (the location of the north magnetic dip pole is considerably removed from both the north geomagnetic pole and the north geographic pole). On that expedition, in July 1959, Kinsey, Don Enemark, and Robert Lamb launched 10 balloons into very high intensities of particles produced by large solar flares.

Balloons as a continuing feature Balloon flights by the Iowa group continued throughout the rest of the decade, both with the huge Skyhook balloons and with much smaller ones.

Balloons are still in use today, primarily to achieve long flight durations at relatively low cost. Flight capabilities have grown dramatically since the 1950s. To illustrate, a new balloon flight duration and distance record was set in early 2005. It involved a flight of nearly 42 days, during which the balloon and its instruments traveled through three orbits around the South Pole. Launched from the National Science Founda­tion’s McMurdo Station in Antarctica on 16 December 2004, it landed on 27 January 2005 after traveling 27,410 miles. The enormous balloon, weighing 4055 pounds, ex­panded to a diameter of more than 450 feet at its ceiling height of 125,000 feet (about 24 miles). The balloon carried a Cosmic Ray Energetics and Mass experiment de­signed to explore the supernova acceleration limit of cosmic rays, the relativistic gas of protons, and electrons and heavy nuclei arriving at Earth from outside the solar

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system. That flight was an early demonstration of the developmental NASA Ultra­Long Duration Balloon, which is expected to extend flight times up to 100 days.19 Balloon sizes are now up to nearly 30 million cubic feet, capable of carrying payload weights exceeding 5000 pounds.20

Summarizing the Iowa experience with balloons during the decade of the 1950s, many Iowa physics students did at least part of their research with balloon-borne instruments. At first, very small, inexpensive latex balloons were used by graduate students Leslie Meredith, Robert A. Ellis Jr., Ernest C. Ray, Kenneth E. Buttrey, William R. Webber, and Raymond F. Missert. By the end of the decade, after the Skyhooks had entered the scene, many additional researchers had used balloons. They included (in addition to the work of McDonald, Kinsey Anderson, Cahill, and McIlwain described earlier) graduate students Hugh Anderson and Ralph Tuckfield. Many of those flights contributed significant new information about radiation in and above the Earth’s atmosphere.

ife within the U. S. space program changed dramatically following the launch of the first Sputnik. The public surprise and outcry following failure of the United States to be first in space energized everyone in a way that no other event short of a war could have done. Their feat vividly demonstrated that the Soviets were capable of launching nuclear weapons over intercontinental distances. The realization that the Soviets really were ahead of us in developing large, long-range missiles resulted in a strong U. S. reaction, and the cold war race for rocket supremacy built to a feverish pitch. The pressure for the United States to get a satellite into space mounted, only adding to the frustrations of the Vanguard personnel, who were having problems in bringing their launch vehicle to a state of readiness.

No account of the early U. S. satellite program would be complete without stepping back in time to examine the fierce competition for developing the U. S. International Geophysical Year (IGY) satellite launcher, the decision to go with the Vanguard proposal, and the persistent effort to keep a losing proposal alive.

did not leave Pasadena for the Cape on 26 January 1958 as planned. I felt that I had to complete the Geiger-MUller (GM) counter calibrations for the Deal II payloads and delayed my departure until the very last minute. I finally left for Florida on Tuesday morning, 28 January 1958, staying overnight in Orlando. Early the next morning the Jet Propulsion Laboratory (JPL) office at Cape Canaveral sent a car to take me, first to Cocoa Beach for check-in at a motel on the strip, and then to Cape Canaveral.

Because of my delay, I arrived there while the first (soon aborted) Deal I countdown was already in progress. I did not view my late arrival as a serious problem, as JPL had the overall responsibility for preparing the relatively simple Deal I payload. I did arrive in time to observe the final Standard Source-Standard Distance check of the cosmic ray instrument in the Spin Test Facility before the satellite was installed atop the launch vehicle.

I had expected to be at some support facility for the countdown and launch where I could monitor my instrument’s performance. I was terribly disappointed to discover that JPL did not have any station available for me. I had no alternative but to join the crowd of general onlookers to listen to the countdown over the Cape-wide public address system.

It was agreed from the beginning that the Vanguard project would compute the orbits for the Deal satellites, as they had already been preparing to do for the Vanguard satellites. After the Deal project was approved in November 1957, tracking data from the JPL Microlock stations were added to the mix. All tracking data were sent to the IBM 704 computer in the Vanguard Computing Center by high-speed wire and radio teletype circuits.

Optical tracking stations An optical tracking system was established as a compo­nent of the U. S. Vanguard program. It drew upon two cooperating components, an acquisition group (known by the name Moonwatch) and a precision tracking group. The acquisition group drew heavily upon the services of amateur astronomers to pro­vide coarse tracking information. The precision tracking component, conceived and overseen by Fred L. Whipple at the Smithsonian Astrophysical Observatory at Cam­bridge, Massachusetts, used high-precision telescopic Baker-Nunn cameras having an unusually large aperture that were developed for the purpose.

Although the camera development was beset by several problems, the network was ready in time to support the Explorer and Vanguard programs. Precision op­tical tracking stations were located at Jupiter, Florida; Organ Pass, New Mexico; Olifansfontein, Union of South Africa; Cadiz, Spain; Mitaka, Japan; Naini Tal, In­dia; Arequipa, Peru; Shiraz, Iran; Curacao, Netherlands West Indies; Villa Dolores, Argentina; and Haleakala, Maui, Hawaii.

In retrospect, the Minitrack and Microlock networks for radio tracking worked well, and the missions probably could have been conducted without the optical tracking net­works. Nevertheless, they provided a layer of protection, using a very basic capability that had the full confidence of the program planners and scientists. Fully integrated into the computational effort at the Vanguard Orbit Computation Center, the optical data were used throughout the early Explorer and Vanguard programs and made a substantial contribution to the high accuracy achieved in tracking those satellites.

Minitrack stations As a part of the presatellite era’s Viking program, the Naval Research Laboratory (NRL) had developed a Single-Axis Phase-Comparison Angle­Tracking Unit. It served as the basis for the development, for Vanguard, of a tracking and telemetry system, known as Minitrack. Two versions of the ground station were developed, a Prime Minitrack Station and a Mark II Minitrack Station.12

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The Minitrack development depended upon the efforts of many NRL individuals, led by John T. Mengel. It included primary contributions by Roger L. Easton, David (Dave) S. Hepler, Victor (Vic) R. Simas, and Martin (Marty) J. Votaw.

All Minitrack stations produced satellite tracking information by the use of pairs of antennas and receivers along both north-south and east-west axes. The outputs of each pair of receivers were summed. When the angle to the satellite was such that its signal arrived at both antennas in phase, the summed output was twice the amplitude arriving at a single antenna. As the satellite moved so that its signal arrived at the two antennas out of phase, they canceled and the sum was zero. Thus, as the satellite made its transit over the station, the combined receiver output for each axis pair was a variable-amplitude signal, with the peaks occurring when the distance from the satellite to the antennas differed by an integral number of wavelengths.

That information was not sufficient to provide unambiguous position information, as the signals were in phase at a number of different angles. In the Prime Minitrack Stations, those ambiguities were removed by using two pairs of antennas having different spacing along each of the two axes.

The Mark II Minitrack Stations, being simpler for implementation by radio am­ateurs and other smaller groups, lacked the multiple pairs of antennas along each axis, and the receivers were much simpler. Their data were used in the Vanguard Orbit Computation Center to complement the data received from the Prime Minitrack Stations.

For reception of the telemetered data, the signals from the pairs of antennas and receivers were combined in a different manner.

The Prime Minitrack Stations also had command transmitters to trigger the play­back of data from the Deal II onboard storage system.

Prime Minitrack Stations were located as shown in the earlier Figure 11.1. Seven stations were located roughly along the seventy-fifth meridian of west longitude and were positioned so that the satellite would pass within range of at least one of them during each orbit. That basic “picket line” consisted of stations located at (from north to south) Blossom Point, Maryland (this station also served as the engineering prototype for development of the system); Fort Stewart, Georgia; Batista Field, Havana, Cuba; Paramo de Cotopaxi, Quito, Ecuador; Pampa de Ancon, Lima, Peru; Salar del Carmen, Antofagasta, Chile; and Peldehune Military Reservation, Santiago, Chile. An additional Prime Minitrack Station at Rio Hata, Republic of Panama, was planned initially, but it was decided that relocating that station at the Navy Electronics Laboratory, San Diego, would meet that need. An additional advantage of the San Diego location was that it was in a better position to receive the signal near the end of the first orbits of newly launched satellites.

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In addition to that basic picket line, Prime Minitrack Stations were positioned at Coolidge Field, Antigua, British West Indies (primarily for downrange reception immediately following launch), and at Woomera, Australia (to provide some very limited coverage in the eastern hemisphere).

Special Minitrack stations with wider antenna beams were established on May – gauana and Grand Turk islands in the British West Indies to assist in tracking the Vanguard first-stage rockets.

A Minitrack station was established by the National Telecommunications Research Center near Johannesburg, South Africa. The primary motivation for that station was to obtain tracking information following injection of Vanguard satellites. It provided valuable tracking information for the Explorer I and III satellites but was not called upon for telemetry data recovery.

Microlock stations As mentioned earlier, JPL had developed a high-performance tracking and telemetry system as a part of their work in testing the Corporal and Sergeant missiles at the White Sands Missile Range in the early 1950s. It operated at very low signal levels (thus, over very long distances), in spite of Doppler shifting of the frequencies of signals received from rapidly moving rockets. That Microlock system was the product of a very energetic and dedicated team under the leadership of JPL’s Eberhardt (Eb) Rechtin. His team included Richard Jaffe, Robertson (Bob) C. Stevens, and Walter (Walt) Victor.13

The Microlock system was sufficiently mature by 1954 that it was introduced into the JPL and Army Ballistic Missile Agency (ABMA) collaborative planning for project Orbiter. Following the end of all officially sanctioned Orbiter planning, the Microlock system remained an integral part of the behind-the-scenes planning for a satellite by ABMA and JPL.

The Microlock receiver was designed with an extremely narrow (10 hertz) radio frequency bandwidth. It employed a phase-locked-loop technique to track the arriving signal’s frequency. For tracking the motion of the satellites, multiple receivers and antennas used the interferometer principle in a manner similar to that described above for the Minitrack system.

A Microlock station was set up at PAFB, Florida, for checking the payloads at Cape Canaveral and for receiving data during their launches. Additional stations were located in Pasadena, California (the developmental station at the JPL home location); Temple City, California (by an amateur radio club, as discussed below); Earthquake Valley, California (at an exceptionally radiation-quiet location); and at Ibadan, Nigeria, and Singapore (for improved global coverage). The locations of the Microlock stations are also indicated in the map of Figure 11.1.

Conventional stations Some early satellite receiving stations were designed in a more conventional manner. The most notable of those was a station established

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and operated by the Radio Research Laboratories at Kokubunji, Tokyo. Although not equipped to provide tracking data, it contributed valuable eastern hemisphere telemetry data throughout the Explorer I and III operating lifetimes.

Radio amateurs Both satellite-launching nations made major efforts to enlist sup­port by the amateur radio community. In the United States, the primary medium for communicating with the amateurs was the American Radio Relay League, through its publication QST. The Soviets used their amateur radio magazine Radio for a similar purpose.

The first to appear in the United States was a pair of articles in the July 1956 issue of QST that dealt with the U. S. Vanguard program’s Minitrack system.14 They were followed over the next two years by a string of articles dealing with equipment and techniques for receiving the signals from the Vanguard satellites.

After the Microlock system entered the picture, radio amateurs were encouraged to receive its signals, as well. The San Gabriel Amateur Radio Club in Temple City, California, went so far as to build and operate a substantial station. The club’s activity was strongly supported by JPL under Henry Richter’s (W6VZA) leadership. The club obtained equipment loans and donations from a variety of sources and facilities and support from the Los Angeles Sheriff’s Department. Members of the club built much of the specialized equipment under the direction of Robert Legg (W6QYY), Lamont Shinn (W6PFR), Jack Pattison (W6POP), and Howard G. Wheeler (W6GRW). Being tightly integrated into the Primary Microlock communications network by JPL, that station provided valuable tracking and telemetered data from the early Explorer satellites. The club documented its work in a handbook that was made available to all interested radio amateurs.15

A Mark II Minitrack tracking and receiving station was established by 12 amateur radio members of the Sohio Moonbeam Group, in Cleveland, Ohio. Other radio amateurs also provided data during the early Explorer flights. Their primary value was in helping to establish the initial orbit parameters.

The Soviets, too, were eager to include radio amateurs in their program. After all, one of the primary reasons for their choice of 20 MHz and 40 MHz as transmitting frequencies for Sputnik 1 was to allow the worldwide community of radio amateurs to receive its signals. That could be done without modifying the receivers possessed by a majority of amateur radio operators. An article in the USSR publication Radio in June 1957 provided technical details about the motion of their planned satellite in its orbit, the propagation of its signal, and arrangements for receiving it. That article was largely unknown in the West until after the Sputnik 1 launch.16 After that occurred, a translation was provided to the International Geophysical Year (IGY) technical panel on ionospheric physics, and a condensed version of that translation appeared

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in QST in November 1957.17 The primary emphasis in that article was on the use of amateur radio observations for orbit determination—telemetry reception instructions were notably absent. For the next several months, QST carried a number of articles dealing in one way or another with Sputnik 1 signal reception.18

As another interesting historical note, during one of our telephone conversations on 27 November 1957, Van Allen mentioned his interest in adding a capability to transmit continuously from the U. S. satellites at a lower frequency to extend the coverage to a wider network of ground receiving sites, including radio amateurs.

The signals at the IGY-approved satellite-transmitting frequencies of 108.00 and 108.03 MHz would propagate only in straight lines. That band had been chosen for just that reason, so that the satellite orbital path could be measured to the desired precision. The straight-line propagation was not important for transmitting the telemetry data, however, and, in fact, limited the area over which reception would be possible. Van Allen knew from his personal experience in receiving the Sputnik 1 signal during his South Pacific expedition that transmission at a frequency of 20 MHz would expand coverage because the signal path would be bent by the ionosphere. He reasoned that it should be possible to meet more of the cosmic ray experiment’s wide-area coverage requirement if a 20 MHz transmitter were added. He stated that unspecialized receiving equipment should permit the reception of the 20 MHz signal for periods of about 25 minutes on each pass, and that it should be possible to receive sequences of at least five consecutive passes.19

The idea was alluring enough that he elevated that question two days later in a letter to the two working groups of the Technical Panel on the Earth Satellite Program (TPESP). That letter advocated continuous 20 MHz satellite data transmission at a level of about 0.1 watt. His letter expressed a set of personal observations, including his belief that a single well-located receiving station could provide telemetry recovery for about one-fourth of the time, that the change would lend itself to added telemetry recovery by radio amateurs and others, and that continuous transmission at that frequency might eliminate the need for onboard data storage in future missions in the interest of simplifying the onboard instruments.

His recommendation was seconded nine days later by Vern Suomi at the University of Wisconsin, who stated that such a transmitter would permit substantial simplifica­tion of the Vanguard instrument he was developing to measure the Earth’s radiation balance.20

Van also discussed this point with Pickering, who once informed me that his working group had discussed transmitting at the 20 MHz frequency from the Deal satellites at an earlier meeting of the TPESP but had decided against it “for political reasons.”

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Nevertheless, by the time of Van Allen’s letter, it was too late to make the change in any of the Deal satellites. His recommendation was implemented later in the Explorer 7 satellite, as related in Chapter 13. As the space program evolved after that, however, the demands for higher data rates from Earth orbit required the higher transmitting frequencies. The specially designed satellite receiving stations became an established feature of space operations, and the possibilities for radio amateur participation dimin­ished. To my knowledge, no other U. S. satellites were designed to transmit at 20 MHz, not even the Oscar satellites that were built by the amateur radio enthusiasts some years later.

Major problems in preparing the ground networks Preparing the network of Mini­track and Microlock stations for the Deal satellites was not without its share of prob­lems. Building the completely new Minitrack system by NRL was a major project in its own right and encountered the typical problems of such endeavors.

The Microlock effort at JPL encountered a major snag at the outset. The Department of Defense (DoD) was initially reluctant to provide the needed financial support. In fact, soon after approval of the Deal program, it issued a directive that limited the Microlock network to the station at Cape Canaveral, Florida (essential for launch support), and the engineering development station in Pasadena. Upon learning of that directive in the early afternoon of Wednesday, 27 November, I immediately called Van Allen. He was, at that moment, preparing for concurrent meetings of the IGY Rocket and Satellite Research Panel and its TPESP to be held on 6 December. He asked me to inform Pickering of that meeting and to tell him that Caltech’s Lee Dubridge would be attending it. He suggested that the two of them might be able to address the problem there.

Pickering immediately set up a conference call that included Henry Richter, Al Hibbs, C. I. Cummings, K. W. Linnes, and me.21 He informed us that, al­though IGY officials had not expressed any opposition to the addition of Microlock (even though it represented a major change in several years of Vanguard planning), they were not willing to openly contest the DoD directive. During that conversa­tion, we identified five possible options for providing the Microlock coverage that we felt we needed: (1) get the DoD position reversed in some way, (2) get ad­ditional coverage without major DoD financial support as a shoestring operation, (3) get the IGY program to help fund it, (4) get IGY participants in India or Japan to set up stations, or (5) see if the University of Iowa could help in some way.

Pickering also sent identical letters to Professor Masasi Miyadi at the Tokyo Astro­nomical Observatory and to A. P. Mitra, secretary of the Indian National Committee for IGY.22 Those letters outlined the need for global telemetry coverage and en­couraged them to construct stations suitable for recovering the Deal telemetry. The

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Japanese did follow through in time to provide valued support by establishing a station near Tokyo, as mentioned earlier.

The next morning, I informed Van Allen that Pickering would be in New York on 5 December to argue the Microlock issue.23 Van offered his help in presenting the scientific basis for increased Microlock coverage and prepared charts to help clarify the issue.

Ultimately, by a combination of continuing vigorous actions and some good luck, a robust network of Microlock ground stations was operational by the time of the Deal I launch.

A second major ground station crisis occurred relatively late in the game. Through a telephone conversation with Roger Easton at NRL on Wednesday, 19 February, just two weeks before the planned launch of Deal II (Explorer II), I learned that the interrogating transmitters were not ready at the NRL Minitrack ground stations, except for the station at Blossom Point, Maryland. The others lacked antenna-matching networks, and about half of them still needed work on the transmitter control panels. That threatened the success of our experiment, as without them we would have been unable to read the data from the onboard tape recorder for most of the orbits. I immediately called Van Allen, who, in turn, called Bill Pickering at JPL and John Hagen, the Vanguard project director at NRL.

Apparently, in the rush of switching our Iowa experiment from the Vanguard program to the Jupiter C program, although we thought the requirement for Vanguard command support was fully understood, no explicit written request for such support had been filed. That omission was immediately rectified by a letter from Pickering to Vanguard’s John Mengel. The text of that letter read:

This is to state that a requirement exists for the operation of interrogation transmitters for the University of Iowa satellite experiment. This payload contains a tape recorder used in connection with the ground interrogation system for the recording and transmission of the complete cosmic ray counts each orbit. It is essential that as many of the Minitrack fence stations as is possible be prepared to interrogate the satellite communications system. The time is very short in which this must be set up. For this reason, details will be worked out in a meeting between us on February 21. If a sufficient portion of the Minitrack system cannot be made available in time, our firing date will have to be delayed in order that a meaningful experiment will result.24

Henry Richter and I made a hasty departure for Washington on Thursday afternoon to be there for a meeting with John Mengel, Roger Easton, and Marty Votaw the next morning. Mengel’s and my independent reports summarized the results. Agreements were reached to retune the Minitrack receivers to the Deal II frequencies and to ready the Minitrack command transmitters for the mission. We received assurance that the Blossom Point, Maryland, station was in operation, and that the Fort Stewart, Georgia; Havana, Cuba; Antigua, British West Indies; Lima, Peru; Antofagasta, Chile; and San

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Diego, California, stations would be ready in time. As parts for the Quito, Ecuador, station had been lost in transit, and the Santiago, Chile, station was dealing with various cable problems, their readiness was in some question.25 26

In reality, it took a heroic effort on the part of the Vanguard engineers and station personnel to complete the arrangements during the short time remaining. Installation and checkout of the command transmitters for the South American stations were performed by Fred Friel of NRL and C. Cunningham of the Lima Station, with Friel hand carrying the necessary parts and instructions. The full array of Minitrack interrogating stations was completed only about a week before the Deal II launch. That seemed then, and even more so now, a miracle. The NRL engineers and operators certainly extended themselves magnificently to achieve that goal.

That January meeting also provided an opportunity to address other details in preparation for the Deal II launch. They included backup procedures for pointing the antennas in case the satellite’s low-power transmitter should fail prematurely, procedures for recording and forwarding ancillary information about interrogation times and performance, and the handling of the ground-recorded telemetry tapes. Henry and I also made a brief stop at the IGY Office in downtown Washington, and we visited the Vanguard Computing Center at 615 Pennsylvania Avenue, Northwest to learn whether all necessary preparations had been made for orbit computation and initial data processing. Henry returned to Los Angeles that evening.

The next morning I had some slack time before leaving Washington for Florida. That gave me an opportunity for some Washington tourism, including walking down the stairs in the Washington Monument. That evening, I flew to Orlando and made my way to Cocoa Beach. On Monday, 24 February, I joined the JPL engineers at Cape Canaveral to help in preparing the satellite instruments for flight.

The United States and Soviet Union were in the midst of the 30-year cold war. By mid-1958, both possessed proven capabilities for producing nuclear weapons and for delivering them by one means or another to the other country. And both were near-paranoid in their suspicions of the other.

Thus, both were urgently examining potential capabilities for detecting the det­onation of nuclear test devices by the other country, and for protecting themselves against atomic bomb attacks if they should occur. In the United States, air filters to remove radioactive debris from the air and airborne water had been developed by the

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Naval Research Laboratory (NRL) as early as 1947.1 Beginning in late 1948, several weather reconnaissance B-29 squadrons routinely patrolled over the Pacific Ocean with those air filters to assist in detecting Soviet test detonations. The first Soviet nuclear detonation, referred to as Joe-1 in the United States and as RDS-1 in the USSR, and occurring on 29 August 1949, was first detected by ground and airborne air and rain filters of that type. The Weather B-29s that I was flying for weather reconnaissance over the Pacific Ocean during 1952 continued that nuclear detonation monitoring effort as an add-on classified mission objective.

Beginning as early as July 1957, our country relied heavily on the Distant Early Warning Line (DEW Line), a network that eventually grew to 63 radar and commu­nications stations built across northern Canada and Alaska to provide early detection of any Soviet aircraft or missiles that might be headed for the United States.

The Soviets announced their successful test of an Intercontinental Ballistic Missile (ICBM) on 26 August 1957. That demonstrated an improved capability for launching nuclear weapons against the United States.

With that new information, Nicholas C. Christofilos, a physicist working on magnetic fusion at the Lawrence Livermore National Laboratory (LLNL, operated by the University of California, Berkeley), became greatly concerned that the Soviets might try to conceal a sneak ICBM attack by detonating a nuclear device beforehand at high altitude. The ionospheric effects and the synchrotron radiation resulting from spiraling electrons produced by the blast might cause radio interference that would severely limit the range at which the DEW Line could see approaching missiles. Conceivably, that particle shell might completely blind the radars.

With the launch of Sputnik 1 on 4 October, Christofilos’ concern heightened. He believed that the new Soviet capability placed the United States in near-term peril. Building on his experience with magnetically confining charged particles, he came up with the idea of depositing and storing huge numbers of electrons in the Earth’s magnetosphere to make a defensive shield. The source of the electrons would be a large number of nuclear explosions at high altitude.

During October and November 1957, he discussed that possibility repeatedly with Herbert F. York, then director of the LLNL. According to York, Christofilos even predicted the existence of the naturally occurring trapped radiation before it was discovered by stating, during those discussions, that “there are already high energy (MeV range) electrons trapped there!” He believed that cosmic rays hit­ting the Earth’s atmosphere produced, among other things, neutrons; some of those moved radially outward and decayed, and a fraction of those were trapped in the magnetosphere.2

Christofilos thought that an electron shell, if produced by the United States, might serve as a defensive electromagnetic shield against Soviet ICBMs. If dense

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enough, it might heat the outer surfaces of approaching ICBMs to make them bright enough targets for heat-seeking defensive missiles. Beyond that was the possibil­ity that a sufficiently dense shell (produced by perhaps thousands of megatons of nuclear detonations per year) might directly damage approaching missiles or their warheads. They might even prematurely and harmlessly trigger incoming nuclear bombs.

His concept became known as the Argus Effect, and the endeavor to test it became known as the Argus Project.