VAN ALLEN, JAMES A.

(b. 7 September 1914, Mount Pleasant, Iowa;

d. 9 August 2006, Iowa City, Iowa), Earth and planetary physics; geophysics; the space sciences; magnetospheric physics.

Van Allen, trained as a nuclear physicist, became a central figure in the study of the upper atmosphere, near-Earth space environment, and the solar system using balloons, sounding rockets, satellites, and planetary probes. He will be chiefly remembered for his discovery of belts of trapped charged particles around the Earth in 1958, and for his leadership in mentoring and advocating the space sciences in the second half of the twentieth century.

Early Life. Born the second of four sons to Alfred Morris and Alma Olney Van Allen, a general purpose lawyer and a former normal school teacher, Van Allen grew up in the small (3,000 population) town of Mount Pleasant, Iowa, in a house built by his paternal grandfather in 1865. His mother had come from a farming family and was of Methodist background, but converted to Presbyterianism upon marriage. His father was an elder in the local church and served as sometime mayor of the town.

Van Allen attended public school and took his first science course as a senior in high school, and enjoyed it greatly along with plane and solid geometry. Upon graduation as high school valedictorian, he followed his older brother to Iowa Wesleyan College, their small hometown college, and lived at home. Through the early and mid-1930s, Van Allen’s father’s law practice more than insulated the family from the Depression. In fact he prospered, prudently purchasing several farms and managing them on a weekly basis, asking his sons to accompany him in his management circuit. Among the many projects Van Allen and his older brother George engaged in as teenagers, Van Allen recalled building a Tesla Coil from plans published in Popular Mechanics.

College Years. Van Allen’s experience in his high school science laboratory carried through to college, stimulating an interest in physics, especially mechanics. His interest was solidified when he came into contact with physicist Thomas Poulter. Poulter made Van Allen his laboratory assistant early on. As a result, Van Allen helped to prepare Poulter’s instruments for the Second Byrd Antarctic Expedition, which occurred a year after the second International Polar Year. Poulter, who had trained in physical chemistry at the University of Chicago, was interested in a broad range of geophysical problems, including meteoritics, terrestrial magnetism, and seismology.

Poulter had borrowed a field magnetometer from the Carnegie Institution of Washington’s Department of Terrestrial Magnetism (DTM). Van Allen’s job was to calibrate it and learn its characteristics and help Poulter learn to operate it. Van Allen accordingly set up a small magnetic observatory on campus and measured the declination of the magnetic needle as well as the total field strength, learning methods from a standard text by Sidney Chapman and Julius Bartels. This turned out to be Van Allen’s first scientific contribution, because DTM did not have such data for his locale. Van Allen extended his work, making a magnetic survey of the county using a theodolite to determine the location of each station. He also assisted Poulter and astronomer Charles Clayton Wylie setting up a series of visual observing stations to determine meteor orbits and radiants. Van Allen recalls that this work was of great influence on his subsequent career, especially in his own expeditionary work, “doing scientific measurements on a geophysical level” (Oral History Interviews [hereafter OHI], 1981, p. 49).

Van Allen graduated in the spring of 1935. Although his parents suggested other possible career paths, such as dentistry, Van Allen was won over by Poulter and by physics, attending graduate school at the University of Iowa, where his father and brother had also attended.

The University of Iowa’s Physics Department, Van Allen recalled, had about twenty graduate students, about half as many as had been in his graduating class at Iowa Wesleyan. Edward P. T. Tyndall was his advisor and directed his first research project growing single crystals of zinc and measuring their mechanical properties, which was in fact his first real test at devising and operating very delicate equipment. This work led to his master’s thesis.

Van Allen now enjoyed access to a broader range of expertise, as well as a full professional library, and began reading the journals. At Iowa Wesleyan he had been a lone wolf, but now he was part of a competitive and active pack of students and he felt the pressure to perform. His life was a single trek between his dormitory room in the Quadrangle and the physics laboratories. Classical physics came readily, but quantum theory and relativity were sufficiently challenging to keep him confined to more familiar experimentation and, as he regarded it, processes that could be directly observed and measured.

Upon completing his master’s thesis, Van Allen switched advisors from Tyndall to Alexander Ellett to take part in Ellett’s project to build a Cockcroft-Walton generator and enter the new realm of experimental nuclear physics. He recalls being fascinated by physicist Hans Bethe’s announcement of his mechanism for energy production in stars, and with Ellett and another student Van Allen engaged in determining hydrogen and deuterium interaction cross-sections, which resulted in a paper with Ellett and Donald Bayley, a postdoctoral student, and finally his 1939 thesis. Experimentation remained Van Allen’s forte; when he attempted to rationalize Bethe’s theory and results in a graduate student colloquium, Van Allen recalled, he was “ripped to shreds” (OHI, 1981, pp. 63–64).

Department of Terrestrial Magnetism (1939–1942). In the spring of 1939, as he neared the end of his thesis work, Van Allen began thinking about what he would do after graduation. By the summer he had three options: one was to join Poulter, who had moved to the Armour Research Foundation in Chicago. He also had met a recruiter from Raytheon who was looking for physicists. Through Ellett, Van Allen was invited to DTM to continue his thesis studies along similar lines: developing and refining ways to count and evaluate particle interactions and new particles arising from proton scattering and deuteron-deuteron reactions.

Van Allen became part of a small group led by Norman P. Heydenberg, another of Ellett’s graduates who was now responsible for one of the van de Graff machines. Van Allen worked on a wide range of projects and enjoyed them immensely, finding the collegiality and the facilities superior to any prior situation. Gregory Breit visited frequently and lectured, collaborating with Merle Tuve, and from these informal arrangements Van Allen began to appreciate far greater horizons in high-energy physics. He began working on determining the photo-disintegration cross section of deuterium and from these successes moved into a wider range of elementary particle experiments, all informed and stimulated by the informal yet exciting atmosphere of the place, under the general direction of Breit and Tuve.

Nuclear physics and fission studies were certainly the most important fields for Van Allen at the time, but he was also keenly aware of the DTM’s strong geophysical traditions. DTM was then directed by John Fleming, who was a dominant figure in geomagnetism and atmospheric electricity, but more influential for Van Allen were people such as Harry Vestine, Scott Forbush, and Julius Bartels, who liked to take contemplative walks with junior staff through the local forests of Rock Creek Park, discussing broad issues ranging from geomagnetism and magnetic storms to statistical analysis. These mentors and other prominent geophysicists who visited from time to time helped to make Van Allen sensitive to opportunities lying at the disciplinary borderlands between experimental nuclear physics and geophysical phenomena, ranging from earth currents and atmospheric electricity to the magnetic field of the Earth. DTM’s very existence and nature fostered such thinking.

War Work (1942–1946). Van Allen’s two-year fellowship was coming to an end about the time that many of his colleagues, such as Lawrence Hafstad and Robert B. Roberts, were quietly moving into another part of the building to engage in war work, following Tuve’s call to switch over. Tuve knew that the British were trying to perfect a radio device that could sense the proximity of a reflective target and decided that his DTM staff could help. Under the aegis of the newly formed Office of Scientific Research and Development (OSRD)—which was headed by Vannevar Bush, the Carnegie Institution of Washington’s president—Tuve formed Section T (for Tuve) that would work on radio proximity fuses. Van Allen did not join at once, partly because Tuve felt he should complete his research fellowship, and by the end of 1941, Van Allen was part of the war effort.

Van Allen worked first on an optical or photoelectric design that was eventually given over to the National Bureau of Standards, and then joined the main DTM effort directed to the radio technique led by Roberts. The radio proximity device had to be designed to be sensitive to its local environment, just opposite what one would want for any normal transmitter, but not so different than a simple motion detector in a common burglar alarm. But it also had to be small, storable, and extremely rugged, capable of withstanding accelerations from 14,000 to 20,000 times the acceleration due to gravity, and here is where Van Allen made his contribution. His task was to work with Raytheon engineers to make hearing aid vacuum tubes as rugged as possible. He set up a small prototype shop soon after Tuve moved his entire enterprise out of DTM to an abandoned Chevrolet showroom in Silver Spring, Maryland, a few miles away, and called it the Applied Physics Laboratory (APL) in March 1942. His basic testing technique was to place the tubes inside 5-inch artillery shells and fire them vertically from navy grounds on the Potomac. They would then retrieve the shells and examine the tubes to see what components failed. Van Allen designed a potting procedure and a miniature spring-loaded support system to reduce mechanical stress, which worked. He received a congratulatory plaque from Tuve, and a $10 bonus for the issued patent. Millions of these tubes were manufactured by Raytheon and Sylvania.

In November, Van Allen and two other young APL staffers were commissioned as junior grade lieutenants in order to accompany the first shipment to the Pacific theater to put the shells into operation. Van Allen’s assignment was to deliver the shells to various ships carrying 5-inch, 38 caliber Mark 12 guns, and instruct the gunnery teams in their use. He was designated assistant staff gunnery officer to Admiral Willis A. Lee, Commander of Battleships, Pacific during his eight months of active duty with the Pacific Fleet, taking the VT (variable time) fuses to destroyers, cruisers, and battleships. He was also involved in evaluating the new shells, finding that they more than met their promise. He saw combat on two occasions.

After his first tour of duty, Van Allen was reassigned the Bureau of Ordnance in Washington to expedite improvements to the VT fuse, working between navy offices in Washington and the APL. After about eight months of this bureaucratic frustration he elected for another tour of duty in the Pacific, this time to establish re-fusing depots on Tulaghi in the Solomon Islands and elsewhere.

Van Allen’s wartime experiences facilitated his “coming of age” not only professionally, but personally. He not only gained critical skills at building and perfecting miniaturized electronic devices and making them work under unbelievably harsh conditions, but he also developed the means for improving the flight stability of these projectiles using a rapid spin-up mechanism that also reduced spin-down during flight. Additionally, he acquired many new human skills, such as managing a broad range of workers and working effectively with varied interests and capabilities. He was proud of becoming an “officer and a gentleman.” More than ever he appreciated the values of, as he recalled in his oral history, “absolute honesty, absolute integrity, meaning what you say, doing what you say you’ll do” (OHI, 1981, p. 104).

His wartime experiences also gave him invaluable training in how to make decisions, using what he called “the method of prudential choices”: faced with having to make a decision but not possessing all possible information, you “must use your best judgment based on the validity and trustworthiness of the evidence you have.” Van Allen had learned, on his own initiative, how one could work through a logical set of branching decisions to reach a conclusion. “I consider that of very basic importance to all kinds of exploratory scientific work” (OHI, 1981, p 105).

Another major watershed event at this time was marriage. Van Allen met Abigail Halsey when he returned from his second tour in the spring of 1945. She was a mathematician and computer at APL; although trained at Mount Holyoke in English literature, Abby was adept at analysis using calculating machines to compute trajectories. They were married in October 1945, and they rented an apartment in Silver Spring. Their first child, Cynthia, was born in January 1947, and they eventually raised five children.

The Applied Physics Laboratory (1946–1950). Van Allen remained in uniform throughout 1945, acting as liaison between the Bureau of Ordnance and the APL, and eagerly accepted an offer from Tuve to rejoin APL as a civilian employee once his military obligations were met. Tuve felt that the DTM owed Van Allen something for ending his fellowship prematurely, and said he could come back and engage in pure research of his choice.

One of Tuve’s senior staff, Henry Porter, kept close contact with trends in the Pentagon and knew about Operation Paperclip and the fact that Army Ordnance was bringing captured German V-2 rockets and rocket parts to the White Sands Proving Grounds to test them and learn from them. Van Allen learned of this program late in 1945 and expressed an interest to Tuve, who accordingly sent Van Allen to a planning meeting at the Naval Research Laboratory (NRL) in January 1946 to see what the army offer entailed. This meeting outlined all the possible scientific experiments that could be done with instruments sent aloft on V-2 flights. Van Allen came away very enthusiastic about conducting cosmic ray research, and Tuve approved his plan to build a new group at APL of about fifteen people who would both instrument V-2 missiles and develop a small rocket that could perform the same function, to sound the uppermost regions of the atmosphere and touch space, performing physical observations of its environment along the way.

Van Allen’s team worked fast and had a cosmic-ray detector ready for the first flights of the V-2 in the spring of 1946. As one of the larger groups preparing instruments for the V-2s, the group was also working on solar spectrographs, gas sampling devices, and diagnostic temperature monitors, as well as developing wire-recorders for in-flight data storage, parachute recovery systems, and, through an APL subcontractor, multi-channel radio data transmitters. By June 1946 his group had grown to sixteen people divided into research and engineering sections.

Over the next several years the APL group proved that it was one of the most capable of the various scientific groups. Van Allen’s cosmic-ray experiments in particular began to return important data on the variation of incident flux with altitude. By 1948 they had established the existence and intensity of a cosmic-ray plateau, a region above 50 kilometers where the flux remained constant and represented an estimate of the nature of the primary flux beyond the atmosphere. Both APL and NRL initially constructed complex cosmic-ray igloos, conical stacks of coincidence and anti-coincidence counters, but soon found that cross-talk and secondary showers confused the results, and overall taxed the telemetry beyond its capabilities. Even though this finding produced useful diagnostic experience for the command and control aspects of missile technologies, it did not contribute to answering questions about the nature of cosmic rays. Van Allen’s team therefore turned to simpler systems that were easier to shield and to assess through telemetered information. Flights in 1947 through 1948 resulted in a refined understanding of the meaning of the plateau.

In 1948, responding to criticisms from physicists about the physical meaning of the plateau, Van Allen and his team launched cosmic-ray payloads aboard their own small sounding rocket, called the Aerobee (a contraction of Aerojet, the prime contractor, and bumblebee), from shipboard at geomagnetic latitudes far different than White Sands. This new phase of their work was in consonance with the Bureau of Ordnance’s interest in developing expertise in shipboard firings of missiles. Although the payload capacity of the Aerobee was far smaller than the V-2, there was enough capability to add other small instruments; Van Allen, prompted by Ernest Harry Vestine and others from DTM, directed his staff to prepare small total field magnetometers to explore the existence of postulated current sheets in the E layer of the ionosphere. From a series of flights at the geomagnetic equator, they discovered what was later called the Equatorial Electrojet. Studies such as these, which were initially mounted to better understand cosmic rays, ultimately led Van Allen and his group into geophysical studies.

Return to Iowa as Physics Department Head (1951– 1985). Van Allen always knew that he and his group were not central to APL’s mission, nor were they, at the working level, fully welcomed by others who were doing the bulk of the bread-and-butter work on missile development. They were called, somewhat sarcastically, Tuve’s “5 percenters,” existing mainly on outside contracts and discretionary funds. After Tuve had moved back to DTM as director in 1946, the atmosphere for basic research at APL deteriorated, and by 1949, his successor Ralph Gibson asked Van Allen to resume supervision of the proximity fuse group. This Van Allen definitely did not want to do, and so he began looking for another job, winning a Guggenheim Fellowship in 1950 that he delayed taking until he knew where he would land.

Van Allen had decided to leave APL by the summer of 1950 when he accepted an invitation from his alma mater, the University of Iowa, to become the chairman of the Physics Department. His fears about continued support from APL were realized after he left: Gibson dissolved his group and reassigned its members to other sections of the laboratory. But Van Allen also did not have any bold promises from Iowa other than the satisfaction of going home and striking out in new territory with the sympathies of the university president for his ambitions to strengthen physics.

Once back in Iowa in January 1951, Van Allen spent the spring and summer using his Guggenheim support to be in residence at Brookhaven National Laboratories, in New York State near his wife’s family. Van Allen was still oscillating between high-energy studies and geophysics, but once back at Iowa in the fall, with research corporation support, he continued high-altitude observations using balloon-launched detectors. He also put into action an idea that he and his APL colleagues had to combine the economy of balloons with the altitude capabilities of rockets, creating the innovative “Rockoon” system of small balloon-launched rocket sondes that could send his small counters to between 80 and 100 kilometers. Van Allen secured enough support from the Office of Naval Research as well as the Atomic Energy Commission, and with navy logistical support mounted an ambitious high-altitude latitude survey of cosmic ray phenomena. Still searching out the elusive nature of primary cosmic rays, Van Allen also gathered critically useful geomagnetic information.

By the time he had moved back to Iowa, Van Allen had assumed the chairmanship of the Upper Atmosphere Rocket Research Panel (UARRP), a small but significant body of activists who represented both military and academic institutions using rocket flights with V-2s, Vikings, and Aerobees to study the upper atmosphere and celestial phenomena. He had also become active in broadly based efforts to explore geophysical realms, even though he was still focused on cosmic rays. A key event took place in 1950 during a visit by Sydney Chapman to the DTM. Chapman, one of the most influential geophysicists alive, was very interested in mounting a coordinated global study of a wide range of geophysical phenomena. During his DTM visit, Van Allen invited him to APL to lecture and hosted an evening dinner party at his Silver Spring home. Chapman wanted to meet various people, including Lloyd Berkner, and Van Allen was happy to accommodate. Out of that dinner party grew plans for what was to become the third International Polar Year but expanded in scope as the International Geophysical Year (IGY). Van Allen would remain a leader in this landmark campaign, and it would ultimately propel him to world prominence.

Pioneering Space Research. It was no accident that Van Allen and his Iowa graduate students were the first to build a satellite payload that returned important scientific information about the Earth’s environment from an orbiting satellite. In the mid-1950s both the United States and the Soviet Union had announced plans to launch satellites; the American contribution was to be a series called Vanguard launched by a multistage navy vehicle that used modified Viking and Aerobee components. Van Allen and his graduate student George Ludwig were literally the first to propose a flight instrument to the chairman of the U.S. National Committee of the IGY. Their September 1955 document, “A Proposal for Cosmic Ray Observations in Earth Satellites,” was not specific about the sizes, weights, or geometries, because the navy had not yet even decided those factors.

Van Allen was clear about what he wanted to do, and campaigned intensively to be granted an early berth. By November he knew that his cosmic-ray detector package was scheduled to fly on an early fully instrumented Vanguard, what eventually became a 20-inch spherical craft. But as he watched the development of the navy program, in his various advisory capacities as the chairman of the Working Group on Internal Instrumentation for IGY satellites of the U.S. National Committee, and as a member of the overall IGY Advisory Committee, Van Allen felt that the probability of Vanguard successfully working was slim. Too many components were new and untested or were upgraded but unproven versions of known technology. He therefore maintained contact with the Army Ballistic Missile Agency (ABMA), mainly with Ernst Stuhlinger, one of Wernher Von Braun’s Huntsville Germans who was particularly interested in the scientific application of space vehicles, to be sure that the payload he and his students were designing would also fit in the “shell” of an ABMA missile (OHI, 1981, p. 219.) If Vanguard fizzled, Van Allen would be ready to fly with the army.

Sputnik launched in October 1957 when Van Allen was “out of town and out of touch” (OHI, 1981, p. 253) on the USS Glacier, roaming south in the central Pacific heading toward Antarctica as part of the IGY’s Operation Deep Freeze, where he and his team launched some three dozen Rockoons. On board ship, Van Allen eagerly devoured the telemetry from Sputnik, convincing himself very reluctantly that its Doppler shifted signal could only come from something in Earth orbit. His diary notes reveal considerable apprehension at being “dealt out” of the action, especially after the launch of Sputnik II and spectacular failure in December of the U.S. answer to Sputnik, a 6.4-inch Vanguard test vehicle carrying only a transmitter. In the wake of the success of Sputnik II in early November, a thousand-pound craft carrying the dog Laika, the Pentagon gave the army a green light to launch its own satellite. After hasty telegrams back and forth with William Pickering at Jet Propulsion Laboratory (JPL), reflecting earlier quiet plans between Stuhlinger and Van Allen, Van Allen’s Vanguard payload was modified by his graduate student George Ludwig to fit into the army’s Explorer satellite even before the Vanguard failure.

This process highlights Van Allen’s centrality to the nation’s nascent space program. As chairman of the UARRP, recently renamed as the Rocket and Satellite Research Panel, and as a leading spokesman for instrumenting satellites during the IGY, Van Allen had both the connections and the track record to be best positioned as the lead instrument provider. The original full-sized Vanguard would have flown a complement of navy high-energy sensors with Van Allen’s cosmic-ray detector, but the Explorer was exclusively Van Allen's—although it did contain a micrometeoroid detector.

The momentum and public equity Van Allen gained as the instrument provider for the first successful American satellite cannot be underestimated. He had a virtual monopoly on the first four Explorers, sending up a succession of cosmic-ray counters. Because of the high spin rate, Explorer I did not carry a data recorder and had no onboard data storage, so it provided data only when in sight of a receiving station. Explorer III, the next successful launch, had data storage and so synoptics could be collected, revealing a fuller picture of the nature of the high-energy particle environment in the highest regions of the Earth’s atmosphere. What Van Allen and his team found was truly astounding: a wholly new component of the Earth’s magnetosphere: a nested set of shells of trapped particle radiation that were soon called the “Van Allen Radiation Belts.” Only after data returned from Explorer IV provided both high-altitude and wide latitude data did the full geometry of the belts emerge.

It is characteristic of Van Allen’s research style that the architecture of the belts emerged gradually. In fact, the team was in such a rush to get the instruments ready that they had no fully worked out methods for data analysis, or even a clear view of what they were really looking for.

Among several factors leading Van Allen to his conclusions was his intrinsic faith in his instruments. Van Allen always prided himself as being a highly successful instrument builder. His overarching design philosophy was simplicity. As various commentators on the high failure rate of space hardware have remarked, the success rate seemed to be an inverse function of the complexity of the instrumentation. Both the NRL and APL groups began with highly complex systems, but once at Iowa Van Allen focused on the simplest devices possible to get the job done. He was also quick to take advantage of newly proven technologies: his Rockoon-based detectors utilized miniature vacuum tube electronics, but when transistors came along, Ludwig used them to reduce the weight of the Vanguard/Explorer payloads by a factor of four. These combined traits of opportunism and simplicity remained with Van Allen throughout much of his subsequent career in the post-Sputnik satellite era, and his successes promoted great faith in his hardware. For instance, when the signals dropped from his counter on Explorer I, he was sure that it was not instrument failure, but was due to something the instruments were experiencing.

Operational Space Research. From the early 1960s through the 1980s Van Allen was principal investigator for a wide range of instrumentation launched aboard Earth satellites as well as planetary and interplanetary missions. He and his Iowa colleagues and a continuing flow of students produced instrumentation for the first Pioneers and Mariners, continuing through to exploring the magnetospheres of the outer planets with Pioneers 10 and 11 to Jupiter and Saturn. He also remained an ardent spokesperson for space research, principally for the importance of unmanned missions in an era when manned spaceflight dominated the public imagination and purse. He always remained keenly aware of the extreme costs involved not only in terms of complexity and infrastructure but in terms of priorities, whether they be for national security, national prestige, or the pursuit of pure knowledge.

Van Allen’s career personified the role of the enlightened scientist in military and government programs and bureaucracies. During his preparations for the first series of Explorers, Van Allen became a key player in high-altitude atomic and nuclear tests involving the remnant directorate of the U.S. National Committee for the IGY, the National Academy and the National Science Foundation, and the Department of Defense. In May 1958, in conjunction with his continued preparations for Explorer leading to a fourth instrumented flight, Van Allen also worked with a wide range of physicists preparing for what was called Project Argus, a military experiment to produce an intense shell of trapped radiation from atomic fission processes that would effectively hinder use of the region for military operations as well as cause a severe disruption in radio communications. The test required high-altitude monitoring, which was the contribution of the Van Allen team. Van Allen undertook this work at the invitation of William Pickering; although his priorities were not identical to those of the Department of Defense and he was not fully aware of the goals of Argus, still he viewed it as useful and another means to assess the nature of the primary component of cosmic radiation as a function of geomagnetic latitude. Argus also provided him the chance to experiment with more complex detector arrays offering improved ways to obtain the cosmic-ray spectrum, identify specific components in the flux, and improve dynamic range.

Van Allen was also part of a small circle of prominent scientists asked to testify during congressional hearings on the establishment of a space agency. He had worked with an Iowa congressman to draft a bill for consideration leading to the creation of a national establishment for space research. He felt that the old National Advisory Committee for Aeronautics (NACA) was a good framework to start with but that the NACA itself had not been distinguished in the scientific use of rockets. Something in the way of a completely new agency was needed, and Van Allen made his views known to Congress and the Executive Branch, pushing for some sort of agency structured like the Atomic Energy Commission with a mixed governing body. The National Aeronautics and Space Administration (NASA) plan that emerged, with a single administrator, was sufficiently close to Van Allen’s views that he heartily endorsed it to President Lyndon Johnson. He was less interested in a military model, an organization associated with the Advanced Research Projects Agency (ARPA), because of the problem with classification.

Van Allen also lobbied to place particles and fields sensors on the early Pioneer probes originally under ARPA/Air Force sponsorship. He wanted to make a vertical cut through the radiation belt system, and with JPL collaboration built the first four payloads. Pioneer IV reached 658,000 kilometers altitude and pierced the belts in both directions. Meanwhile, Explorer instrument pay-loads continued to stream out of the Iowa laboratories finding their way into space, such as aboard the last in the IGY series, Explorer 7, launched in October 1959 by an ABMA Juno 2. This was one of the first of the “heavy payload” satellites with multiple experiments and transmitters arrayed in a thick flat cylinder with conical ends and over seventy pounds of instruments from several institutions in addition to Iowa.

Into Deep Space. The Mariner series gave Van Allen a chance to try out his techniques on the other planets. He was one of a half dozen instrument providers for the first Mariners bound for Venus. Mariner 2, launched in August 1962, recorded the character of interplanetary dust and high-energy particles in its three-and-a-half month voyage. In these and other flights Van Allen’s team continued to utilize collimated and directionally sensitive Geiger tubes to sense proton and electron fluxes and to search for trapped particle fields surrounding Venus, but the instruments failed to detect any noticeable belts. Van Allen keenly realized that what he had discovered surrounding the Earth needed to be searched for around the planets to gain a fuller appreciation of the phenomenon, and had earlier speculated that Venus might harbor trapped radiation belts. Not finding them was an important clue to the differences between the two planets. In 1965 a suite of Van Allen instruments accompanied Mariner 5 back to Venus, this time recording solar x-ray flare phenomena along the way and correlating these with particle fluxes. The Iowa group had sent similar instruments to Mars aboard Mariner 4 and, as in the case of Venus, found only very weak evidence of trapped radiation.

Van Allen was also one of a group of scientists in the mid-1960s interested in sending Mariners to Jupiter, and then using Jupiter’s gravitational field to slingshot them to Saturn and beyond, making a reconnaissance of as many planetary bodies as feasible in the outer Solar System. His own proposal was for a single Jupiter-Saturn encounter, and NASA, the administration, and Congress approved this more modest program. The Mariner Jupiter/Saturn (MJS) was renamed Voyager a few months before their launches in August and September 1977.

Prior to his involvement in MJS, Van Allen was also a principal investigator on Pioneers 10 and 11, the first probes of the outer Solar System. The concept grew out of deliberations he led as chair of the Outer Planets Panel of the Lunar and Planetary Missions Board in the mid-1960s, which led to an initial announcement of opportunity in 1968. Originally intended to go through the asteroid belt and to encounter Jupiter, they were first envisioned as solar powered, but soon were adapted to radioisotope thermoelectric generators (RTGs) used in the Nimbus program. These long-lived power sources made it possible for scientists such as Van Allen and their NASA counterparts to begin thinking of longer-term ventures into deep space, and after launch in March 1972 and April 1973, respectively, Pioneers 10 and 11 visited most of the outer planets.

Iowa instruments measuring particle fluxes and magnetic fields have now flown throughout much of the planetary Solar System, encountering every planet thus far. The Pioneers and Voyagers continued to send back information even beyond the known planetary orbits and throughout the remainder of Van Allen’s career and life. Among many other goals, he harbored the hope that his instruments would detect the shock front between the Sun’s magnetic field and the galaxy, the heliopause, and he lived long enough to witness the first actual evidence of the encounter.

Space Advocacy. In his lifetime, Van Allen did far more than build instruments to probe space. He was a constant advocate for the space sciences since he assumed the chairmanship of the V-2 Panel in September 1947. He saw this body through its many changes until it became the Rocket and Satellite Research Panel and finally became absorbed into the Space Science Board. Van Allen remained external to NASA as a member of a wide range of boards, panels, oversight and review committees, constantly urging policy-making and advice that would maximize scientific return. He hosted a landmark 1962 Iowa conference on goals and priorities for space science, and in 1967 spoke out passionately on how the United States needed to provide greater support for planetary missions. He was a vigorous critic of the space shuttle program, providing congressional testimony during the years 1971 through 1975. He conducted much of this as a member of study panels for the Space Science Board through the decades; one of his later accomplishments was his advocacy, as chair of the Science Working Group, of what became the Galileo mission. His penchant was to remind Congress that despite the focus on high-profile programs fostered by NASA, such as Apollo, the shuttle, or the Space Station, there were important reasons not to abandon robotic missions to the planets, such as Viking or Voyager.

As an advocate, Van Allen keenly knew he was responsible for a burgeoning team at his Iowa home base. He was always careful to align the training of graduate students with his research interests, even as the projects became large-scale and complex enterprises. He was most comfortable with his graduate students in a workshop or laboratory setting, supervising design, fabrication, testing, and then data reduction and publication. Many of the instruments arising from these collaborations became PhD dissertations for his students, like Ludwig, who moved later into NASA. Many of his students remained with him as Iowa colleagues. He also carefully orchestrated the transition his team needed to take when the projects required trained and experienced engineers and administrators. He found a formula that insured that his graduate students would never be far from the data and close enough to the equipment to know how to read the results with the physical intuition he had gained over the years. He remained head of the Physics Department (renamed Physics and Astronomy in 1959) until 1985. He never stopped teaching, including courses in general physics and astronomy as well as specialized courses in solar-terrestrial physics and electromagnetic theory and technique. He greatly enjoyed his introductory lectures in general astronomy that centered upon Solar System topics in a laboratory setting.

Van Allen was survived by his wife of sixty years, Abigail Fithian Halsey, and by their five children, Cynthia, Margot, Sarah, Thomas, and Peter. Except for Cynthia, they were all born and raised in Iowa City. After retirement Van Allen was named Carver Professor of Physics, Emeritus, and in 1990 he became Regent Distinguished Professor. He was a member of the editorial boards of several major journals, and in 1982 became president of the American Geophysical Union. Among literally dozens of honors, in 1987 he was recognized with the National Medal of Science, which was followed by the Crafoord Prize, Royal Swedish Academy of Sciences in 1989, and, in the year of his death, by the National Air and Space Museum Trophy.

BIBLIOGRAPHY

James Van Allen’s papers, comprising more than 200 linear feet of materials, are housed in several collections at the University of Iowa, including his personal papers, “The James A. Van Allen Papers,” and separated administrative and project collections: “The Physics Department Papers Under James A. Van Allen (1951–1985),” “Project Manager Mission Papers,” and “Mission Engineering Papers.” Materials relating to his life and career are also housed at the Carnegie Institution of Washington, the Johns Hopkins University Applied Physics Laboratory, and the National Air and Space Museum, which holds a series of oral histories taken with Van Allen in 1981 totaling some eighteen hours that were central to the writing of this essay.

WORKS BY VAN ALLEN

“Absolute Cross-Section for the Nuclear Disintegration Deuteron Plus Deuteron Decaying to (Proton, Triton) and its Dependence on Bombarding Energy.” PhD diss., University of Iowa, 1939.

“Cosmic-Ray Observations at High Altitudes by Means of Rockets.” Sky and Telescope 7 (1948): 171–175.

With Howard E. Tatel. “The Cosmic-Ray Counting Rate of a Single Geiger Counter for Ground Level to 161 Kilometers Altitude.” Physical Review 73 (1948): 245–251.

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David DeVorkin