Category Dreams, Technology, and Scientific Discovery

he Physics Department at the University of Iowa was a beehive of activity during those early years of the Space Age. James Van Allen provided inspired leader­ship. In addition to his own research, he worked diligently at the task of attracting outstanding faculty, staff members, and graduate students. He had the full support of the greater university, starting at its top with President Virgil Hancher, who gave him constant encouragement and support. During Van Allen’s tenure, he worked tirelessly to improve the department’s facilities, including, ultimately, the addition of a modern new physics building.

The Cosmic Ray Laboratory

Van Allen established the Cosmic Ray Laboratory immediately upon his arrival in 1951 in the old Physics, Astronomy, and Mathematics Building. The center of the campus, the Pentacrest, is anchored by the old capital building in the center, as shown in Figure 15.1. The Physics, Astronomy, and Mathematics Building is to the lower right in that picture.

The Cosmic Ray Laboratory occupied the basement of the south end of that building (to the right in the figure). Although that space served the purpose adequately at the beginning of the balloon and rockoon era, it quickly became overcrowded. By the end of the 1950s, although several other nearby rooms had been commandeered by the laboratory, it became necessary to go so far as to add a floor to the pit of the never-before-used elevator shaft for one of our environmental test chambers and to wall off part of the basement hallway for additional bench space (Figure 15.2).

With Van Allen’s well-established Navy connections, he was able to build an initial capability at very low cost by heavy reliance on military surplus equipment.

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That included everything from basic electronics components, such as resistors and capacitors, to balloons, radiosonde altimeters, machine tools for the instrument shop, Deacon and Loki rockets, and surplus gun mounts used as antenna mounts. It was common in those early days to see students unsoldering components and sorting nuts and screws from old military radio equipment for use in their instruments.

The laboratory’s capabilities grew rapidly after its modest beginning. The Interna­tional Geophysical Year provided a substantial infusion of funds. The Argus-related high-priority Explorer IV and V effort, including the decision to assemble those satellites in our laboratory, brought about a further substantial expansion.

Van Allen, of course, directed the laboratory, including the ever-present burden of assuring its financial support. After their arrival, Frank McDonald and Kinsey Anderson helped in managing the work of the laboratory. During my graduate years, I did much of the ordering and setting up of equipment and oversaw much of the

laboratory’s day-to-day operation. By the end of 1960, it had become a full-fledged Space Sciences Laboratory, including all of the capabilities for developing, building, and testing spacecraft and for processing and interpreting their data.

During that period, the laboratory produced the first university-built satellites. During the next decade, it established a complete satellite data acquisition and com­manding station at nearby North Liberty and a satellite control center on the campus. With those capabilities, the laboratory was able to provide unique student experiences covering the entire gamut of space-related research, from conception of experiments; through development, building, and launching of the instruments; to operating them and deriving and publishing the scientific results.

The laboratory’s early successes, buoyed by pictures in the Iowa newspapers of the cramped laboratory, provided fuel for vastly improving the facilities. In 1964, the laboratory moved into a completely new Physics Building funded substantially by the U. S. space program. That building, shown under construction in Figure 15.1, has been known from its beginning as Van Allen Hall.

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For a time, Van Allen considered establishing a more formally constituted institute. In July 1958, he prepared a four-part memorandum proposing such an institute, addressed to the National Academy’s Space Science Board.1 The four parts of the proposal were titled (1) “Future Satellite and Lunar-Flight Experiments Already Being Prepared at S. U.I.,” (2) “Specific Additional Experiments (1958-1961),” (3) “General Remarks on Other Additional Work (1958-1961),” and (4) “A Proposed INSTITUTE OF SPACE SCIENCE at the State University of Iowa.”

The document was designed to show the overall record of competence and achieve­ment and used that and the promise of continuing leadership as the basis for establish­ing such an institute. It argued the case for shifting from operating on a short range, ad hoc basis to a longer-term structure to provide greater continuity. He proposed that it be organized as an integral part of the academic establishment of the university solely for the conduct of pure research, that its activities be intimately related to the graduate and undergraduate work of the Department of Physics, and that senior persons hold joint appointments on the teaching faculty of the department and on the research staff of the institute. The institute’s primary emphasis would be on research related to primary cosmic radiation, the geomagnetic field, interplanetary plasma, and aurorae. Proposed institute divisions were experimental, theoretical, components and envi­ronmental testing, field operations, and shop. The proposal named eight individuals (including this author) who would form an initial staffing cadre.

Van Allen discussed the establishment of such an institute with several of us from time to time. It was clear that he was weighing the advantages of such a formal long­term arrangement against the added administrative responsibility for sustaining the funding. According to author Abigail Foerstner, one of his additional concerns was the problem of recruiting and retaining a critical mass of key staff members in such a rapidly evolving environment.2 He also harbored some doubts about whether it was really a necessary step in achieving what he wanted to do. After his initial proposal resulted in no response from Washington, Van decided not to push it further.

Although abandoning the concept of a formal institute, he did follow up with a proposal to the National Aeronautics and Space Administration (NASA) soon after its formation for a continuing program of research with satellites and space probes.3 That proposal asked for support on a broad and long-term basis for a substantial body of work. Specifically, it asked for support for (1) data reduction and analysis on a continuing basis, (2) identification of the components of the great radiation belt, (3) recovery flights of nuclear emulsions, (4) long-term temporal and spatial monitoring of intensity in the radiation belt, (5) lunar probe radiation measurements, (6) pole-to – pole orbits, (7) composition and energy spectra of components of the primary cosmic radiation, (8) magnetic field measurements, (9) deep space probes, (10) facilities, and (11) environmental and other test equipment. That proposal was also not funded.

Although NASA did eventually establish institute-like organizations at several other campuses, it adopted the general practice, by and large, of funding university

CHAPTER 15 • PIONEERING IN CAMPUS SPACE RESEARCH 425

research on a mission-by-mission basis through announcements of opportunity for specific missions.4

It is interesting to note that seven of the eight cadre members for the initially pro­posed institute (all of those other than Van Allen himself) moved to work at other insti­tutions during the next several years. Whether the formation of the institute would have anchored some of those individuals in Iowa is one of those unanswerable questions.

Nevertheless, the failure to form an institute, or to obtain funding on a broad sustaining basis, does not appear to have impeded the program at the University of Iowa. The Physics Department has continued to conduct a vigorous program of space research until the present day.

Professor James A. Van Allen served as the instigator and leader of the cosmic ray research program at the University of Iowa.

James A. Van Allen

James Alfred Van Allen (“Van” or “Jim” to his friends) was born and grew up in the small midwestern town of Mount Pleasant, Iowa. The second of four sons of Alfred Morris and Alma Olney Van Allen, he credits C. A. Cottrell, a science teacher at Mount Pleasant High School, with awakening the enthusiasm for science that suffused his entire adult life.

Upon high school graduation in June 1931 as his class valedictorian, he immediately entered Mount Pleasant’s Iowa Wesleyan College, graduating there summa cum laude in June 1935. As a Wesleyan student, he learned of the excitement of hands-on research through his association with his highly esteemed physics professor, Thomas C. Poulter. For his graduate studies, Van Allen went to his “family university,” the University of Iowa, where he received his M. S. degree in 1936 and his physics Ph. D. in June 1939.

Van Allen’s first postgraduation job was as a Research Fellow at the Department of Terrestrial Magnetism in Washington, D. C. That work focused on laboratory nuclear physics but also piqued a growing interest in geophysics that would become his life’s focus. As WWII was intensifying in Europe in 1939, his group switched to development of the then-evolving proximity fuse. Among other tasks, Van Allen oversaw the development of special very rugged miniature vacuum tubes that made such devices feasible (and that later facilitated postwar rocket research). Development of the fuse progressed rapidly, and his group set up the Applied Physics Laboratory of the Johns Hopkins University in mid-1942 to facilitate that work. In late 1942, he was commissioned by the navy to help in deploying the new, highly secret devices into action in the South Pacific and in evaluating their performance.

After the war, Van Allen returned to the APL, where he set up and headed its High Altitude Research Group from then until late 1950. During that period, his group conducted a highly successful research program that included studies of the primary cosmic rays, the solar ultraviolet spectrum, the geomagnetic field in the ionosphere, and the altitude distribution of ozone in the upper atmosphere. In addition to managing the activities of his group, he conducted a vigorous research program of his own. From 1947 on, his record of published papers reflects his growing involvement in cosmic ray research. His studies included the use of the V-2 rockets that were brought to the United States following the war. The first three live firings of the V-2s carried his cosmic radiation instruments, and by the end of the V-2 program, his APL group served as the principal instrumenting agency for 12 of the 63 V-2s that were launched. All 12 of those carried cosmic ray instruments from his laboratory, in addition to instruments to study the other phenomena mentioned above.

As already mentioned, Van Allen was instrumental in the development of the Aerobee high-altitude research rocket. This started with his leading a study of U. S. efforts that might have resulted in new rockets suitable for high-altitude research. His APL work, combined with a similar interest at the NRL, led to a rocket development proposal from the Aerojet Engineering Corporation, a company spawned by the West Coast’s JPL. That resulted in contracts in early 1947 with Aerojet and the Douglas Aircraft Company. Van Allen provided the technical supervision, serving as the agent of the Navy’s Bureau of Ordinance, which provided the financial support for the work.

Thus, by the end of 1950, Van Allen had already established a reputation as a highly skilled researcher and manager. By his direct involvement in the miniaturization and ruggedization efforts involved in producing the proximity fuse and the early rocket instruments, he was a leading instrumentation expert. His publication list from 1947 through 1950 includes eight

OPENING SPACE RESEARCH

papers dealing with technical aspects of rocketry and instrumentation. Fourteen of his papers deal with results from the cosmic ray research. In addition to his personal research, he had provided strong overall leadership in establishing a vigorous research program in the United States. He was poised to play a key role in the development of space research as the second half of the twentieth century opened.

Van Allen and the Iowa Physics Department came together by a wonderfully fortuitous set of circumstances. By 1950, he was at a point in his career where a change of scene seemed desirable. The leadership at the APL seemed to him to be shifting its focus away from pure science research toward research more directly related to defense. At just that time, a vacancy occurred in Van Allen’s alma mater, the University of Iowa’s Department of Physics. Van Allen was offered the position as department head with the rank of full professor, and he arrived on the scene on the first day in January 1951.

His primary research aspiration was to extend his earlier observations of primary cosmic rays to above the substantial atmosphere and to conduct them over a wider range in latitude. He was especially interested in establishing that type of research in a teaching university’s academic environment.

Van Allen remained at the university throughout the rest of his professional career, during which time he and his progression of outstanding students sent instruments to the Moon, Venus, Mars, Jupiter, Saturn, and beyond. During this distinguished career, he served as principal investigator on more than 25 space science missions.

Van Allen especially enjoyed his role as a teacher, both in the classroom and the laboratory. He always treated his students with great respect, learning from them and guiding them with wisdom and kindness.

James Van Allen died on 9 August 2006 at the age of 91 of heart failure after a 10- week period of declining health. He remained actively involved in his research until his last few days.

When Van Allen arrived in Iowa City in 1951, no cosmic ray research program existed there. But the nuclear physics research program in which he had participated for his graduate studies in the late 1930s was still active. The department had a modest electronics laboratory and a small but excellent machine shop.

One of Van Allen’s first actions was to obtain a grant from the private Research Corporation to help get the cosmic ray program started. The objective of that grant was to loft cosmic ray instruments with clusters of small balloons. He also moved rapidly to draw others into the new research effort. He hired Melvin (Mel) B. Gottlieb, then a recent University of Chicago graduate, as a member of the faculty.

The team of Van Allen, Gottlieb, and his first graduate student, Leslie H. Meredith, developed, tested, and flew the initial balloon-borne instruments.

The International Geophysical Year—1957-1958 turned out to be an unqualified success. Nature cooperated, and the Sun went through a particularly active period. Balloons, rockets, and combinations of the two were used to extend observations well into the atmosphere. Earth satellites and space probes permitted in situ measurements above the atmosphere for the first time. Sixty-seven countries participated through the initiative of active scientists in those countries. Those individuals, the world’s most respected researchers, employing the most modern technological equipment of the time, greatly expanded humankind’s understanding of the aurora and airglow, cosmic rays, geomagnetism, glaciology, gravity, ionospheric physics, surveying of longitudes and latitudes, meteorology, nuclear radiation, oceanography, seismology, solar activity, and the upper atmosphere.

The IGY had many lasting effects.43 Many scientific instruments installed on the ground for the endeavor became permanent and provided, over the intervening years, a long timeline of data critically important in understanding long-term global changes. Scientific institutions expanded and new ones were formed, many of which have endured to this day. A whole generation of scientists received their initial training

CHAPTER 3 • THE INTERNATIONAL GEOPHYSICAL YEAR 85

during that period and went on to populate the worldwide Earth and space research endeavors.

As the largest and most successful international scientific cooperative program ever undertaken, the IGY worked out a methodology for a new form of large-scale science to attack problems of global concern. That pattern was followed in conducting more recent cooperative endeavors through such bodies such as the Special Committee on Oceanic Research, the Scientific Committee on Antarctic Research, the International Geophysical Cooperation, the Inter-Union Committee on Contamination by Extrater­restrial Exploration, the Committee on Space Research, the Scientific Committee of Solar Terrestrial Physics, and the International World Days Service, to name only some of them.

The IGY advanced the sharing of data through the creation of a set of World Data Centers that are still playing an important role today. In addition, the vigorous inter­national scientist exchange programs of today are an outgrowth of the success of the IGY in getting researchers to work together across national boundaries. The endeavor fostered a general sense of goodwill and scientific achievement among nations.

In the public arena, the IGY had a positive impact on people’s understanding of scientific research and its importance to society. It expanded their concept of the nature of the universe.

In short, the IGY was a major factor in opening a new era of large-scale, global, collaborative scientific research.

There was a short, stunned silence, and then applause gradually swelled as we began to grasp the reality and immensity of the moment. Reporters rushed out of the room for telephones to contact their papers. The Soviets beamed with obvious pleasure as the first of the many toasts with excellent Russian vodka was offered (Figure 6.2).

Walter Sullivan, science writer for the New York Times, was one of the guests that evening. Moments before, as he had stood in one of the small groups, an embassy

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official informed him that he was wanted on the telephone on the ground floor. It was his paper’s Washington Bureau, and they informed him of their receipt of the news from Moscow. With great excitement, he had bounded up the grand staircase and threaded his way across the ballroom to pass the news to Berkner.

The Soviet conduit for breaking this news to the world was via an Associated Press wire story from Moscow at 6:30 PM EST, Friday, 4 October 1957. According to that account, the satellite had been launched on the first try of a new vehicle, the SL-1 (A) derived from the R-7 ICBM. The satellite was described as a 184 pound sphere measuring 22.5 inches in diameter, with an initial orbital height of 569 miles, inclination of 65 degrees, and orbital period of 96.2 minutes. Its official Soviet name before launch, as mentioned above, was PS-1, standing for Prosteishiy Sputnik, translated “Simple Satellite.” After launch, they referred to it as Iskustvennyi Sputnik Zemli, translated “Fellow Traveler of the Earth.” That was immediately abbreviated for all time as, simply, Sputnik. The satellite transmitted for 23 days. Its orbit decayed on 4 January 1958, after three months of flight.

A RCA receiving station at Riverhead, New York, was the first to hear the satellite’s signal in the United States. There was some initial confusion about the nature of the satellite. Some assumed that the satellite was making many scientific measurements. Others ascribed various sinister purposes to its mission. That confusion need not have occurred, as the Soviets had been quite open about its characteristics from the beginning. The delegates’ comments at the end of the conference on Saturday provided a general description. The most authoritative, more detailed account of the

CHAPTER 6 • SPUTNIK!

satellite’s physical form was provided later by the USSR Participating Committee for the IGY. That description read:

The satellite had a spherical form. Its diameter was 58 cm [22.8 inches] and its weight 83.6 kg [183.9 pounds]. The airtight casing of the satellite was made of aluminum alloy. The surface of the satellite was polished and specially treated. The casing contained all the instruments and sources of power. Before launching, the satellite was filled with gaseous nitrogen.

Moving along its orbit, the satellite periodically experienced widely differing thermal influences; i. e. warming in the Sun’s rays when passing over the sunlit half of the Earth, cooling in the Earth’s shadow, thermal friction of the atmosphere, etc. Moreover, a certain amount of heat was due to the functioning of instruments in the satellite. Thermally, the satellite is an independent stellar body, which maintains a radiant heat exchange with the surrounding space. To provide the normal thermal regime necessary to allow the satellite’s equipment to function during a long period of time was, therefore, in general a new and complex task. The maintenance of the necessary thermal regime in the first satellite was effected by giving its surface suitable values for the coefficients of emission and of absorp­tion of solar radiation, and by regulation of the thermal exchange between the satellite’s casing and the instruments inserted in the satellite by forced circulation of nitrogen in the satellite.

Two radio transmitters installed in the satellite continuously emitted signals on frequencies 20,005 and 40,002 MHz (the wavelengths being 15 and 7.5 m respectively). It should be added that, owing to its relatively large weight, the first satellite was able to house rather powerful radio transmitters. This made it possible for signals from the satellite to be received at great distances and made possible the participation of a large number of radio amateurs all over the globe in the observations of the satellite.

The observations of the satellite’s flight affirmed the possibility of satisfactory reception of its signals by average amateur radio installations at a distance of several thousand km. There were cases when the satellite’s signals were received at a distance of 10,000 km.

The signals of the first satellite’s radio transmitters on both frequencies were in the form of telegraphic messages. The signal on one frequency was sent during the pause in the signal on the other frequency. The duration of each signal was about 0.3 sec. These signals were used for orbital observations [satellite tracking for orbit determination] and for the solution of several scientific problems. In order to register the processes taking place in the satellite, the satellite had sensitive elements that changed the frequencies of the telegraphic messages and the correlation between the duration of messages and pauses with the change of some parameters (temperature and pressure [within the satellite]). During reception, the satellite’s signals were registered for further deciphering and analysis.14

At the cocktail party, the Soviets took full advantage of the ebullience of the moment to extol their country’s technical prowess, and their role in the history of rocketry. One of their staff members detailed to me with obvious pride the accomplishments of Konstantin Tsiolkovsky, their great rocket pioneer. The conversation and toasts continued for a while, but many of the attendees soon faded away, some of them to return to their offices or hotel rooms to ponder the meaning of the event, or to receiving stations to pick up the satellite’s signal.

Homer E. Newell later reported an especially significant postparty gathering. Hugh Odishaw, executive director of the U. S. National Committee for the IGY, who had attended the cocktail party, called Newell, who had chaired the Conference’s Working Group on Internal Instrumentation in Van Allen’s absence, but who had not attended

OPENING SPACE RESEARCH

the cocktail party, to convey the news to him and to see if several of them should get together to discuss the turn of events. Odishaw, Newell, Richard Porter, who had chaired the Working Group on Satellite Launching, Tracking, and Computation, and several others met at the U. S. IGY Headquarters in Washington at 1145 19th Street, Northwest. There, into the night, they followed Sputnik’s course by plotting its ground track on a map as reports were obtained from receiving stations around the world. In a few hours, a good idea emerged of the satellite’s orbit. Newell later reported:

As the group in imagination followed the course of the satellite across the heavens, the members tried to weigh the Soviet accomplishment against the fact that the launching of the U. S. satellite, Vanguard, was still some months away. They tried to estimate what the public reaction would be. Disappointment was to be expected, but they did not anticipate the degree of anguish and sometimes-genuine alarm that would be expressed over the weeks and months that followed.15

There was another notable cocktail party that Friday evening. At Huntsville, Alabama, Wernher von Braun and Major General John Medaris were hosting Neil H. McElroy, the incoming secretary of defense. As McElroy was chatting with von Braun and Medaris, they were interrupted by the Army Ballistic Missile Agency’s press secretary, Gordon Harris, who dashed in to exclaim, “General, it has just been announced over the radio that the Russians have put up a successful satellite.”

After a stunned moment, Von Braun erupted, “We knew they were going to do it! Vanguard will never make it. We have the hardware on the shelf. For God’s sake! Turn us loose and let us do something. We can put up a satellite in sixty days, Mr. McElroy! Just give us the green light and sixty days!” A somewhat more cautious Medaris, upon thinking of all the things that had to be done to prepare for the launch, interjected, “No, Wernher, ninety days.”16,17,18

Thus was begun, in the very hour of the announcement of the Soviet achievement, a frenzied effort to complete the preparation of the Jupiter C launch vehicle to launch a U. S. satellite. It culminated in the launch of Explorer I about four months later.

In another part of the world, James Van Allen and Larry Cahill were on the USS Glacier for their equatorial and Antarctic rockoon launching expedition. On that momentous date, they were near the Galapagos Islands after transiting the Panama Canal and steaming toward the Christmas Islands in the middle of the Pacific Ocean. Van Allen’s account of the receipt of the news was related in Chapter 4.

In late November, Van Allen and I had a series of discussions dealing with the calibration of the GM counters. One of our key experimental goals was to obtain an accurate measurement of the absolute intensity of cosmic rays as a function of orbital position. Good calibrations were crucial to achieving that goal.

Calibration of GM counters was not a new subject. The procedures were well established, not only at Iowa, but also in all laboratories making cosmic ray ob­servations. This topic was discussed in Chapter 1 in connection with Les Mered­ith’s work in helping to establish the cosmic ray balloon program at the Univer­sity of Iowa. His master’s thesis contains an especially detailed discussion of this subject.23

Although the California Institute of Technology enjoyed a rich history of cosmic ray research, the engineers in the satellite program had not shared in that experience. For that reason, and because Van Allen and I were especially concerned about the calibration of the GM counters, I set up the equipment and procedures personally, made many of the runs, and supervised the entire process.

During a 29 November conversation, Van and I discussed the procedures in consid­erable detail. He agreed to send several items that I needed for the purpose, including a laboratory nuclear event counter, the coincidence circuit schematic diagram that I

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had developed there, two actual coincidence circuit assemblies, and several test jigs. He underscored our discussion several days later with a handwritten note that read as follows24:

State University of Iowa Department of Physics Iowa City 12/2/57

Dear George,

1) Rc’d your wire on [cost of] data reduction machinery, etc. I will add to it some for labor, publication, etc. and submit it in the near future.

2) Principal purpose of this note is to remind you of the essential importance of:

(a) Good effective length measurements on Geiger tubes

(b) Absolute efficiency of Geiger tubes for cosmic rays

(c) Counting rate vs. voltage curves (temp. fixed) and counting rate vs. temperature curves (voltage fixed) (preferably for cosmic rays, but since data comes in so slowly that way, at least for radioactive source!)

These tests must be made!

3) If you can send one or two payloads which realistically simulate the Geiger tube’s physical environment we will fly them here for the orientational test (i. e. effect of orientation on Geiger counter rate at balloon altitude). We will supply telemetering transmitter.

Regards,

JAVA

It should be noted that item 3 in that note was never accomplished. Although I carried a spare Explorer I payload back to Iowa City in April, events had overtaken us by that time. We were completely immersed in analyzing the unexpected trapped radiation data, and GM counter orientation information was by then of relatively little importance.

In early December, Van informed me that the laboratory instrument that I had requested was in use elsewhere and not available. That turned out to create a major problem in the light of calibration difficulties that developed later.25

The GM counter calibrations ultimately applied to the Deal I and Deal II instru­ments were extensive. A short list of them includes the following:

• GM counter rate as a function of its applied voltage, typically referred to as the counter’s plateau

• Counter rate variation as a function of counter temperature

• High-voltage regulator tube voltage as a function of temperature (those three calibrations were needed so that we could correct the counting rate for changes in the instrument temperature)

• Counter absolute efficiency for cosmic rays, i. e., the fraction of cosmic rays entering the counter that produce output pulses

• The effective counter length, used for defining its cross-sectional area (those latter two calibrations were needed to compute the absolute cosmic ray intensity)

CHAPTER 8 • GO! JUPITER C, JUNO, AND DEAL I 237

By 11 December, the technicians had assembled the coincidence circuits needed for the later two calibrations, and I made the first absolute efficiency run. Everything appeared to be working properly, so I prepared a set of detailed instructions and turned that operation over to John Collins.26 27

During the following week, I set up and checked the equipment and procedures for determining the counter effective length and turned that operation over to John as well.28 Making those measurements on a number of GM counters continued for several weeks. Reasonable-appearing calibrations were obtained between 28 December and 2 January 1958 for the counters destined for the Deal I payloads.

However, during the second week in January, I observed that the plateau measure­ments that we had begun to make for the Deal II counters were not fully reproducible. It became obvious that spurious counts were being registered during at least some of the runs. That called into question the validity of all the measurements that had been made up to that time, including those for the Deal I counters.

Analysis of the problem required a frustratingly long and tedious effort, in­cluding countless overnight runs. At various times, I attributed the problem to (1) improperly operating laboratory pulse counters, (2) interference from relay contact closures in a nearby crystal oven, (3) contact arcing in a nearby tempera­ture test chamber, (4) possible unstable discrimination of pulse height in the cir­cuit coupling the GM counter to the scalers, (5) unknown background radiation sources in the laboratory, and (6) damage to the GM counters in previous tests. Even after eliminating all of those possibilities, reproducible readings could not be achieved.

The pulse counters being used were standard laboratory instruments, made by Berkeley Instruments. They were designed to determine the frequencies of sinusoidal, square-wave, and other periodic signals, that is, waveforms that repeated in a regular pattern, as opposed to the randomly occurring pulses from our instrument.

On a hunch, on 21 January, I tried the simple expedient of connecting two identical frequency counters in parallel, to see if they would produce identical results. Even though the dial settings were identical on the two counters, their readings were different, and neither one was repeatable. I concluded that the Berkeley counters were too waveform-sensitive and therefore unsuitable for those measurements.

The need for one of the special nuclear pulse counters that I had earlier requested from Van Allen became urgent. I called him with a frantic appeal for one, and he arranged to send it. But it did not arrive for another week.

Meanwhile, I continued with more tests. I improved the coupling between the GM counter and the Berkeley frequency counters. That, too, produced unrepeatable results. I had planned to leave for Cape Canaveral on 26 January for the Deal I launch. But when I finally left the laboratory bench at 2:00 AM that morning in a very discouraged mood, I was compelled to cancel my plane reservations and continue with the calibrations. After a short sleep, I returned to the lab, packed the entire test

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setup in my car, and took it home, where I would be away from all interference sources at JPL. That was no better!

I was getting desperate, as Deal II payload manager Milton (Milt) Brockman was pressing me for the GM counters for the payloads. The following day, the Nuclear Radiation Instruments Model 161 laboratory pulse counter finally arrived from Iowa City. After substituting that instrument, the problem seemed to be solved, and I asked the technicians to proceed with calibration runs for the Deal II counters.

“Seemed to,” because I still had some lingering misgivings. Of course, by then it was far too late to make any further tests or changes on the Deal I instruments, as the payloads were already at Cape Canaveral and the launch was planned for two days hence.

The calibration of the Deal II counters was, from that point on, reasonably straight­forward, and the success with them helped to allay my concerns about the Deal I counters. As it turned out, the calibration of the Deal I flight instrument was shown to be fully valid.

The network of ground stations was the same for Explorer III as it had been for Explorer I. The major difference in operation was that the high-power system was dedicated to telemetering the stored data from the in-orbit data recorder. Since the high-power transmitter had to be turned on from the ground for that purpose, and since only the Minitrack stations possessed command transmitters, high-power system data reception was limited to those stations.

The low-power signal was used in the same manner as for Explorer I, for tracking and for recovering the continuously transmitted data. Although both the Minitrack and Microlock stations had the technical capability for receiving and recording the

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low-power signals, it was decided to depend primarily upon the Microlock stations for collecting those data, thus permitting the Minitrack stations to concentrate on commanding and receiving the high-power data. Although the Minitrack stations used the low-power signal to assist in pointing their antennas, they did not record the low-power data.

The Explorer III operation is summarized as follows10:

• As in the case of Explorer I, there were no problems with the Explorer III primary mechanical structure or with its provisions for controlling its internal temperatures.

• Since the type of whip antenna used in Explorer I had been replaced for Ex­plorer III, there was no recurrence of the antenna abnormalities seen in that satellite.

• The low-power continuously transmitting system operated perfectly from launch on 26 March 1958 until 8 May. During 8 and 9 May, the operation of one of the telemetry channels was erratic, and on 10 May, the radio frequency carrier disappeared. Although the carrier reappeared on 14 May, it was without the subcarrier tones. It disappeared for the last time on 21 May 1958. Thus, operation was normal for six weeks of operation, somewhat shy of its two-month design lifetime. The pattern of that cessation is not completely understood but may have been due to the depletion of batteries.

• Operation of the entire scientific instrument for the high-power system, with its onboard data storage recorder, command receiver, and associated electronics, was also perfect during the time that it was operational. It operated perfectly for 44 days, until 9 May 1958, when responses to interrogations became intermittent. Response to interrogations ceased completely on 12 May but reappeared briefly on 21 May. The final response was received on 24 May. The 44 days of normal operation again fell short of the design lifetime by about two weeks but were long enough to satisfy all of the mission requirements. The behavior pattern for the high-power system around the end of life was also not completely understood. It is partly explainable by the large number of command attempts that were made during the satellite’s early life, since energy from the telemetry system batteries was consumed each time a command was received by the satellite, whether the data were observed on the ground or not.

• The fact that erratic operation of the entirely independent low – and high-power telemetry systems began at about the same time led to speculation that some external event may have been involved. However, no abnormalities in instrument temperature or radiation intensity were observed during the days leading up to 9 May, so such an event was probably not a factor.

CHAPTER 11 • OPERATIONS AND DATA HANDLING

The secretiveness of the Soviets caused them to miss discovering the Earth’s radiation belts. There have been recurring debates about bragging rights to the basic discovery and to the finding that there were two distinct regions of trapped radiation.54 55

Sputnik 1 carried no scientific instruments (other than those for internal temper­ature and pressure engineering measurements), and so, of course, had no way to detect the trapped radiation. On the other hand, Sputnik 2, launched on 3 November

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1957 (well ahead of Explorers I and III), did carry two GM counters that no doubt responded to the intense radiation. That satellite’s orbit, with an apogee height of 1131 miles and orbital inclination of 65.3 degrees, was admirably suited for detecting and studying the radiation.

But the Soviets did not receive data from regions where the higher readings would have been seen. Their data-receiving stations were located within the northern hemi­sphere, mostly within the Soviet Union, where the satellite was at its lowest height— generally below the trapped radiation.56 To compound the situation, the Soviets did not make information available that would have enabled scientists outside the Soviet Union to work with the satellite data.

The Soviets did obtain a single reading of a mildly increased intensity from Sputnik 2. A station in the northern USSR, on 7 November 1957, showed an increased radiation intensity, by about 50 percent. The indication was similar in general character to the measurements of the auroral soft radiation seen by the Iowa group during their 1953, 1954, 1955, and 1957 rockoon expeditions. Those auroral zone high-intensity readings were centered at about 68 degrees geomagnetic latitude, as shown in Figure 2.14, and at altitudes above about 50 miles. The Sputnik 2 anomaly was seen at a geomagnetic latitude of about 55 degrees over the Soviet Union, at a height of about 188 miles.

It was recognized during 1955-1957 that particles producing the soft auroral readings were being at least funneled into the polar regions by the Earth’s magnetic field. In fact, some of the enhanced radiation may have been from electrons captured in durable trajectories in the Earth’s magnetic field. Therefore, it is possible that the soft auroral radiation may have been the first weak manifestation of the presence of the outer radiation belt. We certainly did not arrive at that conclusion at the time, and never took the position that the detection of the soft auroral radiation represented the discovery of the Earth’s trapped radiation.

The single anomalous Sputnik 2 reading later served as the basis for the frequent claim by the Soviets that they discovered the outer radiation belt.

The first known report of that reading was by Academician A. V Topchiyev, chief scientific secretary of the Soviet Academy of Sciences, who reported at its annual meeting beginning on 25 March 1958:

Observations of cosmic rays by the satellite gave evidence of the variations of the intensity of its radiation. These variations evidently are connected with the condition of the interplanetary medium near the Earth. One case of a sharp rise to 50% of the number of particles of cosmic radiation was observed. Excellent agreement of readings of both instruments exclude the possibility of explaining this case as due to errors in the apparatus. At the same time, cosmic ray ground stations did not detect a substantial increase in cosmic ray intensity at this time.

At present, a detailed study of this occurrence is being made. It is possible that they are caused by a new phenomena [ліс], namely, by generation of cosmic rays of very low energy on the Sun which are strongly absorbed by the Earth’s atmosphere.57

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A full-page article in the 27 April 1958 issue of Pravda presented a compilation of results of the experiments conducted by Sputniks 1 and 2. It included a brief mention of the 50 percent increase in intensity mentioned above. The new article repeated the earlier assertion that it may have been a burst of radiation from the Sun.58

Our public announcement of the discovery of the high-intensity radiation was made on 1 May 1958. The paper on which the lecture was based, as well as the lecture itself, clearly attributed the high-intensity radiation to particles trapped in the Earth’s magnetic field. It was later universally agreed that Explorers I and III had observed the lower fringe of the inner radiation belt, with satellite orbital inclinations too low to see the outer cusps of the outer radiation belt.

The story of Sputnik 3 must have been especially galling to the Soviet scientists. That was the satellite that they first designed as their ultimate contribution to the IGY. Being very large and complex, its development required a tremendous effort. The Soviet support institutions and officials were slow at first in rising to the design task, and its schedule slipped month by month. It finally lagged so much that the Soviet hierarchy began to fear that the United States would beat them into space.

As early as January 1957, Sergei P. Korolev, the leader of the Soviet Intercontinental Ballistic Missile (ICBM) rocket program, suggested the development of two satellite versions: the full one envisioned by the scientists and a simpler one that came to be known internally as the Simple Satellite. In August 1957, after the R-7 ICBM successfully propelled a dummy H-bomb warhead over 3500 miles to Kamchatka, Korolev argued to the State Commission for the ICBM, and then to the Presidium of the Central Committee of the Communist Party, for the quick launch of the simpler polished sphere. With their nervous acquiescence, he pushed the preparation of that satellite forward in time for the 4 October launch.

The launch of their more complete IGY satellite was delayed still further following the resounding success of Sputnik 1. Soviet Premier Nikita Khrushchev finally realized what a politically hot property he had and instructed Korolev to launch something new in space in time for the next anniversary of their revolution. That goal could not be met with their primary satellite. By setting aside all normal procedures for designing and producing a new object, his team was able to prepare Sputnik 2 with portions of the leftover Sputnik 1 hardware, and with its dog as added cargo, in less than a month. It was launched on 3 November 1957.

After that, things started coming together for the launch of the much-anticipated larger scientific satellite. The first attempt on 27 April 1958, however, failed. The rocket engine quit at about eight miles’ height, and the satellite separated from its launcher and tumbled to the ground.59

A second launch attempt finally placed Sputnik 3 in orbit on 15 May 1958. But there was another problem. During the prelaunch checkout, the onboard tape recorder

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did not appear to be working properly. Two stories exist about the decision to proceed with the launch in spite of that difficulty. The first is that the recorder’s chief designer, Alexei Bogomolov, supremely confident of his creation, suggested that the testing failure was caused by electromagnetic interference from the many radiation sources in the test room and recommended that the countdown continue.60 The second version is that the order to launch came to Korolev directly from Premier Khrushchev, who wanted the satellite launched before the Italian general elections on 25-26 May, in the belief that that display of the superiority of Communism might help the Italian Communist Party in that election.61 It is possible that both factors played a role. In any event, the launch took place, and it was found that the tape recorder had, indeed, failed, thereby denying them access to data from other than the regions surrounding their ground receiving stations.

Sputnik 3 carried a very impressive array of scientific instruments, including detec­tors that were easily capable of showing the presence of the high-intensity radiation. As in the case of Sputnik 2, however, the array of Soviet ground receiving stations did not include significant coverage outside the Soviet Union. The failed onboard tape recorder did not provide data from the regions where most of the indications of the high-intensity radiation would have been seen. Those shortcomings would have been somewhat ameliorated if the Soviets had made the technical information needed to decode the satellite data available to the outside world. But their obsession with making their satellites appear to the world as unaided triumphs of Soviet Communism made it impossible for outside radio amateurs and eager IGY colleagues to provide additional data.

The 15 May launch of Sputnik 3 was followed by a series of reports of satellite performance in the press and scientific literature. For example, Pravda, on 18 May 1958, carried a full two-page article on Sputnik 3. That article, however, was limited to a general description of the program, of the instruments, and of the planned scientific program and included no mention of scientific results.62

A new Soviet reference to anomalous radiation was finally published in Tass in mid-July. It continued to ignore the U. S. announcement in May of the trapped radiation discovery. That Soviet announcement read:

Thanks to the instruments installed in Sputnik III a new phenomenon in science was discov­ered, a special type of corpuscular radiation which up to now had not been observed in the

composition of cosmic rays. Specialists are now engaged in puzzling out this phenomenon.63

The written papers provided by the Soviets for the Symposium on Rockets and Satellites at the Fifth Meeting of the Comite Speciale de l’Annee Geophysique In­ternationale, Moscow, on 30 July to 9 August 1958, made no mention of particle trapping. But Sergei N. Vernov, during a specially arranged evening address, dis­cussed the Sputnik 2 and 3 results beyond the written papers. The best account of

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Soviet information actually presented at the symposium is contained in the summary prepared by William Kellogg soon after the symposium. He reported that Vernov’s evening discussion, as it related to charged particle results, dealt primarily with the traditional cosmic rays.64

According to Kellogg, in that evening lecture, Vernov described the anomalous readings as observations of the “electron component of the cosmic rays” and made no mention of particle trapping. Specifically, he reported that Sputnik 3 had seen variable but high intensities of radiation that often exceeded the dynamic ranges of their detectors over the Soviet Union (in the latitude range from 55 degrees to 60 degrees north). He suggested that the increased flux was likely due to bremsstrahlung radiation from electrons interacting in the material of the satellite and detector and outlined two possibilities for their source. The first was that the elec­trons might be accelerated near the Earth by electric fields like those assumed to exist in aurorae. His second suggestion was that the electrons might originate away from the Earth, possibly on the Sun, and that they penetrated through the Earth’s magnetic field because of irregularities in that field. Van Allen later reported “that [Ernest] Ray had attended the Fifth General Assembly of the IGY from July 30-August 9, 1958, and heard papers by Vernov and Alexander Chudakov, the first exchange of Russian and American scientists regarding the radiation belts. They offered no re­port on the outer belt and no graphic rendering of the belts as shown in Van Allen’s reports.”65

The information presented by Vernov at the symposium was modified and con­siderably expanded in a paper by him and his colleagues that was later widely pub­lished. That paper, appearing well after the Moscow Symposium, contained the first known Soviet mention of charged particle trapping in the Earth’s magnetic field, stating:

Apparently, two types of variations occur. One type of the variation is caused by cosmic rays, and it must therefore respond to changes in the number of primary cosmic rays. The other type of variation does not concern cosmic rays. Apparently, a new type of radiation, and a variation of the intensity of charged particles and photons caused by this radiation were recorded on the satellites with the help of the apparatus constructed for the study of cosmic rays. This variation is caused by the radiation which can be called “earth radia­tion,” i. e., the particles of high energy originating near the earth and rotating around the earth.

A. I. Lebedinskiy and one of us (S. N. Vernov) considered the possibility of storing a large number of secondary particles near the earth. These particles are able to move quasi­periodically from one hemisphere to another. In the first approximation, the motion of the particle in the magnetic field must take place in such a way that the magnetic moment of the particle will be constant. Therefore, a charged particle is “trapped” in the region of a relatively weak magnetic field. These particles are able to perform a large number of oscil­lations and their intensity must be very large. One source of particles is the decay products of neutrons emitted by the earth under the action of cosmic rays. On the other hand, it is possible that particles from corpuscular streams emitted by the sun may also be such a source.66

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Thus, the situation at the end of the Moscow Symposium in early August 1958 was that the U. S. results from Explorer IV substantiated the earlier discovery of trapped radiation by Explorers I and III. The data were, however, still too sparse to infer the existence of two separate radiation zones. The Soviets were still very tentative in their explanation of the anomalous readings that they had received from Sputniks 2 and 3, had not yet attributed them to particle trapping, and had not postulated two separate regions of radiation. That latter conclusion awaited southern hemisphere data from Sputnik 3 and data from the U. S. Explorer IV satellite launched on 26 June 1958 and from the Pioneer 3 space probe launched on 6 December 1958.

Van Allen much later summarized the situation: “In retrospect, I should say that both the Soviets and we independently did have the basis—as of late August—for speculating on the structure of the [outer] radiation zone. But neither group had the perspicacity to do so at the time.”67,68

There is little doubt that, if the Soviets had openly included the world’s scientists and others in their endeavor, useful Sputnik 2 data would have been available from lower latitudes and higher altitudes—most importantly over South America and the South Atlantic Ocean. With that, the new phenomenon might well have become known as the Vernov Radiation Belts instead of the Van Allen Radiation Belts. Even without those data, if the recorder on Sputnik 3 had worked, the outer belt could have become known as the Vernov Outer Radiation Belt.69

Being solar powered, Sputnik 3 provided scientific data for about a year. In the fall of 1958, some data from south of the equator began to become available to the Soviet scientists. The Soviet research vessel Ob reached the southern hemisphere and began providing data in September. Also in September, the Soviets shared their radio code with Australian researchers, who began providing data from the region where the satellite was near its greatest height, and therefore, ideally sited to provide valuable data on the radiation belts.

The point at which it can be claimed that the outer belt was discovered remains a question of interpretation.

The model established at the beginning of the Space Age by the University of Iowa and several other universities clearly set the pattern for vigorous direct participation in space research by the academic community. Before the highly successful first U. S. satellites, some believed that only larger governmental and industrial laboratories would be able to build the scientific instruments. However, our cosmic ray instruments in Explorers I, II, and III provided an early demonstration that universities could handle the task in a very competent manner.

In addition to building those first individual instruments, the expanded university role on the Explorer IV and V project demonstrated that universities could handle entire satellite projects. Satellite S-46 was a more ambitious multi-instrument payload that was designed and largely built there. After that, the first in a series of Iowa-built Injun satellites, launched on 29 June 1961, transmitted useful space radiation data for nearly two years. Injun 2, a launch failure, was followed by fully successful Injun 3 on 13 December 1962, which operated for nearly a year. Injun 4 (Explorer 25) orbited on 21 November 1964, and Injun 5 (Explorer 40) was launched on 8 August 1968. Hawkeye 1 followed seven years later in June 1975.

Injun 5 represented the first fully all-university built and operated satellite. Al­though some data from the earlier Iowa satellites were recorded locally, NASA’s worldwide network carried the primary burden for satellite operation and data recep­tion. For Injun 5, however, the University of Iowa built and operated a major command and data acquisition station atNorth Liberty, several miles north of Iowa City. To make orbit-wide data recovery productive by that single station, Injun 5 (as had Explorer III) employed an onboard tape recorder. From a control center on the campus, the univer­sity students and staff were fully responsible for satellite operation and data recovery.

Iowa’s leadership role in conducting space experiments has continued to the present day. A 2004 tabulation prepared for the celebration of Van Allen’s ninetieth birthday lists 73 instruments that the laboratory had produced up to that time.

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Thus, Iowa, along with the university laboratories at Wisconsin, Chicago, Minnesota, and Stanford, played a major role in establishing the principle that universities could be relied upon to provide space hardware.

Leslie (Les) H. Meredith was born on 23 October 1927 and lived during most of his childhood in Iowa City. He received most of his college degrees from the University of Iowa: his B. A. in 1950, his M. A. in 1952, and his Ph. D. in 1954, all in physics. His timing was fortunate, as he became Van Allen’s first graduate student.

During parts of 1953 and 1954, Les went to Princeton University to work with Van Allen on the Matterhorn nuclear fusion project.6 Upon receiving his Ph. D. in 1954, he began his postgraduate career at the Naval Research Laboratory (NRL) in Washington, D. C., serving

CHAPTER 1 • SETTING THE STAGE AT THE UNIVERSITY OF IOWA 9

as head of the Rocket Sonde Branch and Meteor and Aurora Section. After the National Aeronautics and Space Administration was signed into law in October 1958, Les became one of the cadre of scientists transferred from the NRL to form what became the Goddard Space Flight Center in Greenbelt, Maryland. Serving for 12 years as chief of its Space Science Division, he provided outstanding leadership in the buildup of Goddard’s research staff and program. By mid-1970 he took over as deputy director of the Space and Earth Sciences Directorate, and after October 1972, he served for nearly three years as Goddard’s assistant director.

During subsequent years, Les moved through a progression of upper-level management positions, culminating in a short tour as the Goddard Center’s acting director. After his retirement as a federal government employee, he worked for nine years with the 13-agency U. S. Global Change Research Program.

In 2003, he and his wife, Marilyn, moved to their retirement home at North Myrtle Beach in North Carolina. Marilyn died in 2008, but Les has continued to reside there.

Les’ early balloons were launched from a football practice field on the east bank of the Iowa River from 16 June 1951 (beginning only five months after Van Allen’s arrival) through 26 January 1952. His scientific objective was to measure the incoming cosmic ray intensity as a function of altitude with a directional telescope using thin-walled Geiger-Muller (GM) counters. A concomitant purpose was to help the department gain initial experience with counters and coincidence circuits, telemetering techniques, and balloon flying.

That first Iowa balloon apparatus employed an array of three in-line, thin-walled, cylindrical, Victoreen-type 1B85 GM counters, with a coincidence circuit to form a directional telescope. An event from the center counter was counted, but only when the top and bottom counters were triggered at essentially the same time. Thus, only particles traveling vertically through all three counters were registered. The output of that telescope, along with an altitude measurement, was sent to ground by a frequency-modulated (FM/FM) telemetering system adapted from a design originally developed by Thomas Coor at Princeton University.7 Height-measuring barometers and transmitters taken from surplus weather radiosondes were included. Meredith’s circuits employed 13 miniature acorn vacuum tubes, each measuring about one-half inch in diameter and one and one-half inches in length.

His apparatus, with batteries, was assembled in a frame constructed of one-half inch, lightweight angle stock riveted together to form a boxlike structure measuring 15 by 15 by 30 inches. The gondola was completely covered with celluloid and partly covered with white paper to control the temperature of the instrument during its several-hour flight.

A number of inexpensive Darex type-J weather balloons of about six foot diameter were used to loft the instruments. Multiple small balloons were used rather than a single larger one. Not only were the smaller ones less expensive, but their use also freed the flights from the tight constraints of the Federal Aviation Administration— the larger balloons would have presented a potential hazard to aviation, whereas the smaller ones would not endanger the aircraft. The number of balloons was chosen so

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that their net free lift was about twice the total weight of the gondola and its rigging. For a payload weight of 27 pounds, a typical arrangement included nine balloons, each with 6 pounds lift.

Some of Les’ recollections about these earliest developments are entertaining and revealing.8 He stated, “The system test… was to take [the instrument] to the first high hill that you came to on the highway going south along the river, I think it was about five miles out of town, and then turn it on. The signal strength and counter operation were then checked at the receiving station, which was located in the attic of the physics building.” He continued, “Each balloon was of… some kind of rubber that had to be boiled just prior to launch to be flexible.” Recalling the field operation: “At launch, with the balloons at an angle because of any breeze, I and a helper ran with the payload until the balloons were high enough so the gondola wouldn’t swing down and hit the ground.”9

Out of Meredith’s seven flights in that series, the first two, flown on 16 June and 6 July 1951, produced somewhat noisy but usable data. Flight 3 failed to produce any usable data. Flights 4, 5, and 6 were flown with simple test equipment instead of with the more valuable instruments in order to work out some of the remaining technical details. The seventh and last flight in the series, launched 26 January 1952, produced good data throughout most of the flight. Preparation for the launch of the final flight is shown in Figure 1.1.

The three productive flights in this series served as the basis for Meredith’s master’s thesis, in which he established a new value for cosmic ray vertical intensity at that latitude for particles above an energy threshold that was lower than had previously been measured.10

he program of the International Geophysical Year—1957-1958 (IGY) provided a unique opportunity for cosmic ray research in general, and for us at Iowa City. As an active leader in the overall planning, James Van Allen had helped to shape both the general and specific character of the IGY program. In that role, he provided a great service to the research community.

In our Physics Department, Van Allen set the stage for the next few years of research. Acting to take advantage of the tremendous opportunity, he met in early 1956 with his graduate students to discuss possibilities for projects that they might undertake for their thesis work. By Carl McIlwain and Larry Cahill’s recollections, the list of possible projects that he placed on the table in that session included six cosmic ray, two auroral soft radiation, and two magnetic field studies.12 He envisioned that they could use a variety of balloons, ground-launched rockets, rockoons, and satellites. Those suggestions were in addition to the cosmic ray satellite experiment which he had proposed, and on which I had already begun work.

Following that session, decisions were made quickly, and specific proposals for IGY projects were submitted to Washington and funded. The work was undertaken with great enthusiasm and energy by the department’s graduate students, faculty, and staff.

Ground-launched rockets

The Iowa IGY research program, as it evolved, included experiments employing a mix of ground-launched rocket, balloon, rockoon, and satellite instruments. Carl McIlwain initiated the rocket program with an ambitious plan to probe the northern auroral zone.

89

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Mcllwain’s Fort Churchill flights At the time of the graduate student meeting, Carl was completing the work for his master’s degree. He received that in June 1956, with a thesis based upon the data from his Loki rockoon flights during the summer 1955 Davis Strait expedition.3

Van Allen’s suggestion that Carl might take advantage of the IGY program to fly some Nike-Cajun rockets at Fort Churchill, Canada, caught his attention, and he began thinking about various possibilities. He was captivated by the possibility that those rockets might be able to directly detect the particles that created the aurora, and thus shed light on the particle composition and energy spectra. It was known at the time, based on the alignment of the visible auroral features with the Earth’s magnetic field, that the auroral light was due to charged particles entering the Earth’s atmosphere. It was also known that at least some of those particles were protons in the 100 keV energy range, based on the presence of Doppler-shifted H„ and Hg spectral lines. The earlier direct detection of the soft auroral radiation by State University of Iowa (SUI) rockoons, however, indicated the presence of electrons, and Carl was eager to follow up on that new information.

To emphasize once again the trust placed by Van Allen in his graduate students, he assigned projects to them and then gave them tremendous freedom in seeing them through to completion. In this case, he designated Carl as the SUI chief scientist, and Carl bore full responsibility for preparing the instruments and conducting the field operation.

Carl’s first major technical challenge was to devise detectors that could detect and measure the very soft radiation that was capable of penetrating only very small amounts of material. Developing those instruments occupied much of 1957. He was joined in that work by Donald (Don) Enemark, a second-year electrical engineering student, and Donald (Don) Stilwell, an undergraduate physics student. They developed and built instruments capable of detecting the low-energy electrons in time for two Nike-Cajun flights that were scheduled for late summer 1957. Carl is shown working on one of his instruments in Figure 4.1.

Carl’s apparatus included three charged-particle detectors, a photometer, and a magnetometer. The first particle detector employed a thin thallium-doped cesium iodide (CsI [Tl]) scintillator crystal mounted on the face of a photomultiplier tube. Apertures, plus a 400 gauss permanent magnet, prevented electrons with less than 1 MeV energy from reaching the scintillator. The light sensitivity of the scintilla­tor crystal was reduced by a coating of 40 microgram per square centimeter alu­minum that was evaporated on its surface. Although the detector was sensitive to both protons and heavier ions, such as alpha particles, it was referred to as the proton detector.

The second particle detector was designed to characterize electrons. It, too, used a CsI (Tl) scintillator on the face of a photomultiplier tube. This one was annular in shape, with a thick plastic baffle filling the center opening. A ring aperture was located ahead of the detector, and an electromagnet between the aperture and scintil­lator focused electrons having specific energy ranges onto the scintillator. The pulses produced in the photomultiplier tube were integrated, and the resulting current was passed through a nonlinear network to produce a current that was roughly propor­tional to the logarithm of the electron energy flux over the range from 10-2 to 10+2 ergs per second per square centimeter per steradian. The magnet current was se­quenced through seven steps to make the detector sensitive to electrons in various energy ranges. The highest magnet current focused electrons with energies in the neighborhood of 100 keV The crystal on that second detector, too, was covered by a thin coat of aluminum to reduce its light sensitivity. That coating set the lower energy sensitivity of the detector at about 3 keV

A Geiger-Muller (GM) counter was included in the particle detector complement. It was surrounded by a one-sixteenth inch thick lead shield, except for a slit located

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next to a thin aluminum window in the side of the instrument package. It was sensitive to directly impinging electrons having energies in the range of 1 to 5 MeV In addition, it served as a low-efficiency detector for lower energy electrons through the process of converting electrons to X-ray photons (bremsstrahlung) in the atmosphere and the mass of the instrument. That arrangement provided a way to relate the new measurements to those made earlier with GM counters on the rockoon flights.

Carl included a photometer to measure the total directional intensity of visible auroral light. And a flux-gate magnetometer assisted in determining the pointing direction of the detectors during flight. Finally, a narrowly focused photometer was used on the ground during the flight to measure the auroral intensity straight above the launch site. In addition to being used to interpret the data, its output was used to help determine the best times to fire the rockets.

Carl’s two inaugural flights ran into difficulties. In the first firing (rocket number II 6.22F on 27 August 1957),4 the Nike first stage had not quite completed its burn when the two stages separated, and the Nike nudged the Cajun enough to break off the instrumented nose cone. Carl later reported that he found the payload in the muskeg the next day, and some of the electronics were still operable. His second flight (rocket II 6.23F on 30 August 1957 to a height of 70 miles) was somewhat more successful. The payload reached an aurora, but the Cajun, by chance, was pointing the instruments downward during the critical portion of the flight. Thus, he was not able to observe the incoming auroral particles.

Early the next year, Carl was ready with four more instruments of the same design. When he arrived at Fort Churchill, he found Les Meredith, who was by then working at the Naval Research Laboratory (NRL), with Leo Davis, also from NRL, already there with low-energy detectors that they had developed for flight on Aerobee-Hi rockets. They had made a successful flight (rocket NN 3.03F on 20 January 1958 to a height of 112 miles) by the time that Carl arrived and triumphantly announced that they had “already found what causes the aurora—low energy electrons, and that Carl might as well go home.”5

Believing that there was still new information to be gained, Carl proceeded, never­theless, with the checkout of his instruments (Figure 4.2). He made four flights during a 13-day period in February (II 6.24F on 13 February 1958 to 80 miles, II 6.25F on 16 February 1958 to 75 miles, II 6.26F at 05:34 UT on 22 February 1958 to 80 miles,6 and II 6.27F at 05:48 UT on 25 February 1958 to 80 miles). Fortuitously, a large solar flare occurred during the night of 11 February, a few days before his launches. It was quickly followed by a severe magnetic storm at the Earth, marked by decreases in the cosmic ray and neutron monitor intensities. That night was also marked by a bright red aurora that was observed over a large range of latitudes and longitudes. The following two weeks were characterized by moderate magnetic activity and frequent

occurrences of high-latitude visible auroras. The weather conditions at Fort Churchill were good throughout most of that period, permitting excellent observations.

Carl’s first three flights were technically successful, but data were obtained from only relatively dim and quiescent auroras. The flight on 22 February, for example, produced excellent data on the flux and energy spectra of protons and electrons but was not located in a very active region.

Those results were tantalizing, but not really what Carl was looking for. He de­cided to make a special effort to place his last rocket into a more active aurora and played the waiting game during the next several nights. His account of that launch read:

So, just visualize the scientists who were waiting around for me to get my last rocket off so they could fire theirs, and the impatience of the range safety people. Even though a graduate student, I still had control of when to launch. I told them, “Things are still not quite right.”

We waited at T minus 5 minutes night after night, and they said, “Come on, there is some aurora up there. Fire the thing,” but I insisted on waiting, and was very lucky. Upon seeing an auroral breakup just to the south of Churchill, I finally decided it was the time to finish the countdown.7

That launch (II 6.27F) finally took place in the early morning of 25 February 1958, and the Cajun reached observing altitude just as the aurora appeared over­head. The instrument remained pointed upward during the time of peak interest and

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produced the first-ever direct measurements of particles producing a bright auroral display.8

Enormous fluxes of low-energy electrons were detected, but they had an energy spectrum substantially different than had been seen earlier by both Les Meredith and Carl in the more quiescent auroras. Whereas the earlier measurements had revealed a broadly spread spectrum, the spectrum from this flight showed a strong peak at about 6 keV Carl concluded that the electrons had fallen through an electric potential that must have had a component aligned parallel to the magnetic field lines. That finding was highly controversial, as most of the theoreticians were quite convinced that it was impossible to have an electric field aligned parallel with magnetic field lines in a plasma. So he was hesitant about putting that conclusion into print, but did so somewhat later. Although still not universally accepted, the strong preponderance of belief today is that parallel electric fields do, in fact, exist and that they serve as a prime driver for the auroral particles.

I have tremendous admiration for Carl and his work. Following his arrival at Iowa, he very rapidly gained a deep understanding of physical processes when photons and charged particles move through space and interact with matter. The accomplished musician had become a virtuoso physicist!