Category Dreams, Technology, and Scientific Discovery

There was a substantial delay, sometimes exceeding three weeks, between the record­ing of data at the ground receiving stations and appearance of the data in our Iowa City laboratory. That was due, of course, to the time required for the shipment of data tapes from the widely spread sites, for clearing customs in some cases, for some limited processing and examination of the data at JPL, and for shipment of the tapes and charts from JPL to Iowa City. As of 5 February, the date on which I left Iowa City on my way back to Pasadena after the Explorer I launch, none of the Explorer I data had yet reached Iowa City for analysis.15

Even after the next week or two, only a sparse set of data was available. It consisted mostly of short segments (of the order of a minute each) from stations widely dispersed geographically. The positions of the satellite at the times when those bits and pieces were recorded were uncertain, as the accuracy of the satellite orbit computation in Washington was still evolving.

Even by the end of February, the situation remained quite tentative, as seen by examining an SUI progress report released on 28 February.16 Sanborn strip-charts from 74 passes over Microlock stations had been received from JPL. Of those passes, all but seven were from U. S. stations, that is, from locations where the satellite was near its northernmost excursion and not far above its lowest height, that is, outside the region of trapped radiation.

In addition to the Sanborn charts, magnetic tapes with copies of the appropriate channels from the ground station recordings had been received for 66 passes. In most cases, those were not the same passes as those for which the Sanborn charts had been received.

By 23 February (the cutoff date for the data analysis that was summarized in the 28 February progress report), SUI had examined, read, and plotted the data from 54 of those passes. Thirty-four (largely from stations in California, where the satellite

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was near its lowest altitude) produced clean and readable data. They showed cosmic ray counting rates within the expected range of 12 to 80 counts per second.

Although a substantial number of tapes from the Naval Research Laboratory’s (NRL’s) Minitrack stations had arrived at JPL by that time, none of them had been processed. Thus, none of the recordings made during deep excursions into the region of intense radiation were yet available.

The 28 February report did briefly mention a curious anomaly:

An apparently valid case of a temporal variation was observed in a record from the J. P.L. receiving station at 0123 UT on 2/5/58 [5 February]. An inadequate amount of data has been received to confirm the Japanese report of temporal variations at 0709 UT on 2/5/58 and at 0857 UT on 2/7/58. Reports of apparent temporal variations must be viewed with caution since the normal counting rate varies markedly with latitude and altitude.17

The complete tabulation of Explorer I data published much later reveals that the JPL pass mentioned here had shown a normal rate until about mid-pass, when it began edging upward, reaching 109 counts per second at the end of the pass. Thus, it was making a very shallow approach to the trapping region. Final analysis of the Tokyo passes revealed that the rate peaked at 324 counts per second and then decreased to a normal rate during the 5 February pass. The tabulations reveal that no data were received from Tokyo or any other station on 7 February at the time cited above. Thus, the one Tokyo pass did also indicate a mild incursion into the trapping region.

Records from Singapore and Nigeria deserve special comment. A later assessment revealed that the instrument had frequently risen well into the high-intensity radiation region over those stations during the 24 day period covered in the 28 February report. Such incursions occurred on 8 days at Singapore and on 14 days at Nigeria. However, no significant portion of those data had yet reached Iowa City by the time of the February report.

As a side note, the tapes mentioned above were just the beginning of the torrent of Explorer I data that eventually descended upon our laboratory. During just the period from launch through 23 February, a final total of 474 station recordings were of good enough quality that the beginning and ending times of radio frequency signal reception were eventually determined. Of those, 334 yielded at least short bursts of useful cosmic ray data. By the end of the satellite operational lifetime, the accumulated totals grew to 877 and 592, respectively.

In summary, the report on 28 February indicated satisfactory performance of the Explorer I instrument and included a few guarded comments about what were being referred to then as “temporal variations.” The general situation in Iowa City at the end of February can best be characterized as a mixture of jubilation that we were receiving useful data from the first U. S. satellite, frustration that we were not receiving

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the data more quickly, and perplexity about several mildly abnormal readings. The photograph on the cover is an accurate portrayal, even though staged sometime later, of the puzzling situation that existed at that time.

The first Deal II launch attempt was made on 5 March, but the satellite failed to enter orbit, as related earlier. I stopped at Iowa City over the 8-9 March weekend on my way back from the Cape to Pasadena. Our small cosmic ray group gathered in the physics building that Saturday to discuss the early Explorer I data. Van Allen, Ernie Ray, and I were joined by Carl McIlwain, who had recently returned from his Fort Churchill rocket-launching expedition and had just joined the Explorer I data effort. The three of them, with help from student data readers, had been trying to make sense of the unexpected “anomalous” readings.

The situation remained additionally clouded by the continuing lack of accurate orbital information, since minute-to-minute satellite orbital positions from the IGY Vanguard Processing Center had also not yet started to arrive. Joe Siry and his people in the Vanguard Computing Center in downtown Washington were working heroically but were still having difficulties in computing an accurate orbit, partly because the software and tracking system were new and had to go through a period of initial shakedown, but also because the orbit apogee was substantially higher than expected.

To further complicate the situation, both the tasks of interpreting the data and computing the orbit were complicated by the transition of the Explorer I motion from its initial axial spin to an end-to-end tumbling, as described in the previous chapter. The signals from both the high – and low-power satellite transmitters, although they were operating at their full design power levels, were very weak by any ordinary standards. The deep spin modulation that resulted from the change in the spin configuration resulted in additional dropouts in the data that complicated their interpretation.

Thus, even by the time of my 8 March visit, we still possessed only isolated segments of Explorer I data, mostly with durations of a minute or less. And the locations of the instrument in space where the data had been captured were uncertain.

Despite those factors, a discernable pattern was emerging. There were periods during which the counting rate was as expected from the primary cosmic rays, other periods during which the counting rate was much higher, and still other times during which the counting rate appeared to be zero. One especially intriguing case had been seen of a smooth transition during a station pass from a zero counting rate, to a high rate, and then to a normal cosmic ray rate.

My clear recollection of that 8 March meeting is of the four of us (Van Allen, Ray, McIlwain, and me) gathered around the conference table in Van’s office for an extended assessment of possible causes of the strange readings. The moment was later reposed and captured on film, and that photograph became the model for a 1962 painting by artist Robert Tabor that still hangs in Van Allen Hall at the University of Iowa.

OPENING SPACE RESEARCH

Either there was some systematic misbehavior of the instrument, or we were seeing a real physical phenomenon that was completely unexpected. We pored over every possibility we could think of to explain the anomalous rates. We debated, for example, whether the unusual observations could be the result of temperature effects on the GM counter or associated electronics. But there was no correlation between the anomalous rates and the passage of the satellite through the Earth’s nighttime shadow, where the instrument temperatures dropped to their lowest values. The only consistent correlation appeared to be with the satellite’s position relative to the Earth’s magnetic field. The high and zero apparent rates seemed to occur consistently only when the satellite was both closest to the magnetic equator and at its highest altitudes.

In preparing for the Fort Churchill expedition from which he had just returned, Carl Mcllwain had wanted to find out how his detectors would respond to the high-intensity radiation that had been seen in the auroral zone during our earlier rockoon expeditions. To do that, he talked Van Allen into buying an expensive 250 KV direct current X-ray machine and set it up in the north end of the basement. His preexpedition calibrations revealed that that machine could easily drive the GM counters to zero counting rates.

During our March meeting, Carl noted that the zero counting rates being seen in the Explorer I data seemed similar to those he had seen during the calibration of his Churchill instruments. He suggested that the Explorer satellite instruments might be observing a high flux of particles that was blanking the GM counter. He further suggested that study of transitions from normal to abnormal rates might help resolve the riddle. Abrupt transitions would suggest an instrument malfunction, while smooth transitions would suggest that the satellite was moving into and out of a region containing a high radiation flux.18

Thus, at that 8 March meeting, we were already beginning to seriously entertain the possibility that there might be a higher than anticipated flux of charged particles in certain regions above the atmosphere. That information, however, was held very closely to our collective chests until we could be more certain of the situation. Not even other members of the physics faculty were aware of the development at that time.

The Iowa satellite experiment as originally envisioned did not call for any particular urgency in dealing with the flight data. As previously stated, its original purpose had been to assemble a set of data that was comprehensive in its spatial and temporal coverage. We envisioned that the data set would be assembled throughout the satellite’s lifetime and that the analysis process would be done in due course during the following months.

We had no way of anticipating the intensity of the spotlight that soon focused upon our work. The cold war space race introduced a new reality—pressure for early

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results precluded the more measured pace that had been envisioned. Added to that, the unexpected readings created in us an even greater sense of excitement and urgency. We were beginning to understand that we might have come across a new finding of great importance.

During the weeks following our 8 March meeting, while I was busy at JPL with preparations for the second launch attempt of our more complete Deal II instru­ment, Van Allen, Ray, and McIlwain, with a team of student data readers, continued their examination of the Explorer I data. Nevertheless, the data remained largely in­conclusive.

No indication of our growing belief in the possible existence of a naturally occur­ring region of high-intensity radiation appears to have been made at the previously mentioned 11-12 March meetings at JPL. Throughout the rest of that month and early April, there were other external contacts in which preliminary results from Explorer I were discussed. On 20 March, for example, Van Allen talked to a CBS reporter about our results—again, there is no indication that the anomaly was mentioned.19 On 17 March, I talked to a physicist at Northrop Aircraft who was working on a paper on radiation hazards in space. During that discussion, I outlined our general progress to date but made no mention of elevated counting rates.20

Van Allen wanted to be sure of our analysis before mentioning it outside our group.

In the general excitement that followed the successful Explorer I launch, a new satellite program was approved and announced that would capitalize on the now-proven launch capability. The program, with Juno II as the vehicle name, would use a larger Jupiter Intermediate-Range Ballistic Missile instead of a Redstone as its first stage, combined with the Juno I upper stages. It would be able to launch a substantially heavier satellite. On 17 March, Van Allen informed me that our Iowa group would be furnishing an instrument for that so-called IGYHeavy Payload.

Its initial schedule called for a very short developmental period. We were expected to have our instrument prototype ready by 1 June. Thus, the development of our new instrument became an urgent priority for me. As circumstances evolved, that instrument was not actually launched until over a year later as Explorer 7 (after an intervening failed attempt). But those delays could not have been foreseen during the period March through May, when I had to scramble to meet the original schedule. The story of the development and launch of that satellite is recounted in Chapter 14.

Meanwhile, time marched inexorably toward the second attempt to launch Deal II. The Deal IIb payload was launched from Cape Canaveral at midday on 26 March (12:38 EST or 17:38 UT), as described in the previous chapter. After launch, it was renamed Explorer III.

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y the end of the summer of 1958, less than a year after the first penetration into space, three successful Sputniks had led the venture into the new realm, accompanied by three Explorers and a Vanguard satellite.

Both the Soviet Union and the United States quickly tooled up for the unfolding grand adventure and opportunity. In the United States, the Department of Defense established, in February 1958, a new agency for focusing their space program—the Advanced Research Projects Agency, later renamed the Defense Research Projects Agency. In addition to oversight of the Argus program, as described in the previous chapter, it began vigorous work on the reconnaissance satellites that had been a long-standing aspiration of the military and other national intelligence-gathering organizations. It also began to address the urgent needs of the Department of Defense for improved worldwide communications.

A new U. S. agency to oversee the nation’s civilian space program was signed into law on 1 October 1958, just before the first anniversary of the Sputnik 1 launch. That National Aeronautics and Space Administration (NASA) took over responsibility for the scientific missions then in progress and quickly expanded its scope to encompass a vast array of robotic and manned endeavors.

This chapter concentrates on the rapid blossoming of instrumented space research during the rest of the decade of the 1950s.

A major balloon launching campaign was mounted in the spring of 1956, when three flights were made at Iowa City with larger skyhook balloons.49 50 Frank McDonald and Bill Webber had quickly followed their balloon flights on the second Goodfellow expedition with the development of an improved instrument. It contained a thin-lucite Cerenkov detector like the one used previously, but augmented by a Na-I scintillation counter and a GM counter telescope to provide improved measurements of lithium, beryllium, boron, and carbon in the primary cosmic ray radiation. The entire package, along with a camera to record the data, was assembled in a cylindrical aluminum gondola six feet long, 18 inches in diameter, and weighing 130 pounds, as shown in Figure 2.16.

The first two of those launches lofted a large assortment of experiment instruments. On the first flight, the new McDonald-Webber instrument led the chain of packages on the load line. The next package on the line, designed by Laurence (Larry) J. Cahill, constituted an early balloon flight test of the proton free-precession magnetometer that he had been developing for rockoon flights, as detailed in Chapter 4. Next on the line was one of Kinsey Anderson’s GM counter telescopes like the ones he had just flown at Goodfellow. Yash Pal, an Indian research associate at the Massachusetts Institute of Technology, provided a bundle of photographic nuclear emulsion plates. Additional items included a timer and cut-down device for terminating the flight after eight hours, a parachute for lowering the string of instruments after they were cut loose, a camera,

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an altitude-measuring barometer, another bundle of nuclear emulsion plates from the University of Minnesota, and a carefully calculated ballast to control the equilibrium altitude of the balloon. Those components, totaling about 250 pounds, were spaced along the balloon’s 100 foot long load line.

The largest Skyhook balloon used to date, at 244 feet in length before inflation, about 150 feet in diameter when fully inflated, and nearly 2 million cubic feet in volume, was used to loft the first of the three Iowa flights. That first launch was initially planned for about 1 March 1956 but was delayed because of weather. Another attempt was made to launch it on 12 March, but high winds and poor visibility caused further postponement. The launches required a ground wind speed of less than 11 miles per hour to avoid damage to the balloons and their loads during inflation and launch. It was also highly desired that the visibility across eastern Iowa and northern Illinois be clear to enable the chase teams to follow and recover the instruments.

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All conditions were met the next day, when it was finally possible to launch that first Super-Skyhook balloon from a runway at the Iowa City municipal airport. That occurred at 7:47 AM on 13 March 1956.51 The experimenters had made final checks and adjustments on their instruments throughout the night. The balloon-inflation crew began their preparations soon after midnight. Four foot weather balloons were tethered from a panel truck at 150 foot and 300 foot heights to monitor the wind speed and direction. Although the lower test balloon indicated a gentle enough wind for safely inflating the balloon, the higher one revealed a wind shear that could destroy the balloon soon after release. That situation persisted throughout most of the night. As dawn approached, the wind shear finally abated, and a decision to attempt the flight was made at about 5:30 AM. The fleet of vehicles made its way into position at the south end of the runway. That flotilla included a truck pulling the mobile launcher, another truck carrying helium, the panel truck with its weather balloons, the scientists and their instruments, and the beginnings of an entourage of onlookers that eventually swelled to more than 200. Just before the Sun appeared over the eastern horizon, the balloon was laid out on the runway and inflation began. As inflation progressed, the envelope was played out from between large rollers on the mobile launcher. As the helium bubble slowly formed, the flow was stopped at intervals and the platform was pushed forward by the tow truck to play out more of the plastic envelope.

There was great excitement in the local community about this launching. Batteries of newspaper photographers snapped their cameras as the crews worked through the night, and local radio station KXIC began a live broadcast at about sunrise. The growing crowd of onlookers pressed in on the workers—it was too early in the Space Age for us to have thought much about crowd control. As the free lift reached about twice the payload weight, the flow of helium was stopped. At that time, the helium was contained in a small bubble at the very top of the balloon. Although occupying only about 1 percent of the balloon’s volume at ground level, this bubble would expand as the balloon ascended through the decreasing air pressure until it completely filled the balloon’s spherical envelope at about 113,000 feet, or 21 miles. Until it was cut down by the timer, the balloon would float at about that altitude, moving up or down slightly as the gas temperature varied due to changes in solar illumination.

After everything was ready for the balloon release, a hold was called. That lasted for an hour while the pressing crowds were moved back and the launch platform was realigned to accommodate a slight shift in the wind direction. Finally, one end of the launch platform’s top roller was released, and the balloon floated free. Being at the top of the load line, Frank’s gondola was immediately lifted from the ground. Since the wind was blowing the balloon slowly northward, the other teams had to run across the ground with their equipment packages until the balloon took up the slack in the load line. Otherwise, the instruments would have been dragged across the ground and damaged. This was always an exciting (often comical) phase of a balloon

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launching operation. There is no greater motivation for an Olympian sprint than a graduate student’s need to thus protect the prized product of many months of intense laboratory preparation, and to keep alive his hopes for a timely completion of his thesis and receipt of his degree.

The chase plane departed immediately after the launch. The assembled crowd watched the balloon and its payload shrink to a small dot in the sky and eventually disappear. Cahill and an undergraduate assistant departed to chase the balloon with a truck on loan to the Physics Department from the Navy. They followed the balloon eastward, stopping about every 50 miles to record the payload signal, until they were stopped by Lake Michigan. A full discussion of that flight of Larry’s instrument is contained in the thesis for his M. S. degree, which he received in 1957.52

The other experimenters rushed back to the physics building, where Kinsey Anderson was able to monitor the radio signals from his instruments until mid­morning, when the balloon passed out of radio range. Frank McDonald’s data were being recorded by a special camera in the gondola, so he could do nothing but await the gondola’s return to see if his instruments had performed satisfactorily. The nuclear emulsion plates, of course, also needed to be returned for laboratory analysis.

High-altitude winds turned out to be much stronger than expected. Within the first 200 miles, the balloon had far outpaced the chase truck. It reached upstate New York by the time the timer cut the load line and the parachute lowered the payload to the ground. The chase plane was out of visual contact due to thick weather much of the last portion of the trip, but the pilots were able to follow the balloon’s approximate path with the plane’s radio direction finder. They believed that the balloon’s equipment had descended about 40 miles south of Rochester, and so landed at the Rochester airport. A ground search, however, was unsuccessful. It wasn’t until 48 days later, on 30 April, after a snow cover melted, that a farmer found the equipment 30 miles south of Utica, about 120 miles farther east than expected. The equipment was returned, the farmer was paid the promised reward of $150 for finding and reporting it, and Frank and the other scientists began to analyze their flight data.53

The second and third flights used somewhat smaller 120 foot diameter balloons. The primary instrument on the second flight was another of Frank McDonald’s heavy – nuclei cosmic ray instruments. It was in a gondola similar to that of the first flight, but somewhat lighter at 110 pounds. Carl McIlwain flew a single GM counter package sim­ilar to the ones he had launched on the 1955 rockoon expedition. Also attached to the load line were nuclear emulsion packages from the University of Minnesota, Washing­ton University in St. Louis, Missouri, and the Massachusetts Institute of Technology.

The second flight was launched at 6:27 AM on 20 March. Everything went more smoothly, the balloon’s speed aloft was more nearly as expected, the skies were clear,

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and the twin-engine Beech chase plane was easily able to follow it. After seeing the equipment string descend under its parachute about seven miles northwest of Mount Pleasant, Michigan, the pilots landed their plane at the nearest airport. People on the ground also saw the instruments descend, and the flight equipment was in the hands of the Michigan State Police 20 minutes after it landed. The pilots in the chase plane returned the equipment to Iowa City the following day.54

For the third flight, graduate student Raymond (Ray) Missert had prepared for a long-duration 24 hour flight to study variations in the cosmic ray intensity. Available records do not contain details of that flight, but it appears to have taken place, as Ray obtained his Ph. D. degree the following year based on a dissertation on that subject.55

Those three flights were supported once again by the ONR and the Atomic Energy Commission. The balloon operations were handled by Otto C. Winzen, chief flight engineer Edward Lewis, and their crew from Otto’s Winzen Research Company in Minneapolis. The Iowa experimenters were assisted by a battery of student aides and other assistants.

This chapter relating balloon, rocket, and rockoon work rounds out my account of University of Iowa high-altitude scientific research to the point where the International Geophysical Year provided an opportunity for a greatly expanded program, including the possibility of launching artificial Earth satellites. The balloon, rocket, androckoon work described in this chapter produced important scientific results, sharpened our technical skills, and shaped a high-altitude research laboratory that was second to none.

I received my bachelor’s degree at the winter convocation in February 1956 and was ready to begin my graduate work. My personal involvement with the Iowa balloon and rockoon programs, per se, essentially ended when I turned to developing Earth satellite instruments in March 1956.

Since the data recorder developed for Vanguard and launched on Explorer III played such an important role in the radiation belt discovery, a few more words about the device are appropriate.

Variations on the Iowa design Variations of my recorder design were developed by two other groups. Starting in late 1956, Gerhardt Groetzinger and his group at RIAS in Baltimore, Maryland, designed a Vanguard instrument package with an ionization chamber for measuring the flux of primary cosmic ray nuclei with atomic number greater than eight. He, too, needed to obtain broad orbital coverage. In May 1957, I sent him a full set of drawings and an actual working model of my recorder (unit 2 of the Mark III design), as well as my electronic circuit designs. He used that material as the basis for a version for his instrument.

Unfortunately, Dr. Groetzinger died before his instrument could be launched. That ion chamber, with P. Schwed of RIAS and Martin A. Pomerantz of the Franklin Institute serving as investigators, was eventually launched aboard Explorer 7 on 13 October 1959. Explorer 7 employed a solar-powered, continuously radiating, rel­atively high power 20 MHz transmitter that could be received by radio amateurs via conventional receivers throughout the world. Thus, adequate coverage by direct radio transmission was expected, and their tape recorder was not needed in that satellite.

For many years, I enjoyed a wonderfully productive relationship with Verner (Vern) E. Suomi at the University of Wisconsin. He first contacted me in mid-1956 about the possibility of using my recorder and electronic circuit designs, and I immediately provided a full set of drawings and other details. His “Proposal on Radiation Balance of the Earth From a Satellite,” which included a variation of my recorder design,

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was submitted in the early fall as a candidate for flight in the Vanguard program. He received preliminary endorsement from the IGY committee in early December 1956. On 25 February 1957, they received formal approval and funding for their proposal, and a month later, they reported that fabrication had begun on their tape recorder – sequencer. Their variation on the design increased the recorder tape speed to two steps per second instead of one and added an elaborate set of sequencing switches that cycled between five sensors and two 10-stage scaler circuits. Those switches were actuated by the ratchet drive in the tape recorder.

An attempt was made to place the full University of Wisconsin instrument into orbit on 22 June 1959 on Vanguard Satellite Launch Vehicle (SLV)-6, but that launch attempt failed. A modified version of the instrument was finally orbited aboard Ex­plorer 7 on 13 October 1959. Since that satellite benefited from global reception of the higher-powered 20 MHz transmissions, as mentioned before, the data recording feature was not needed and dropped. However, the stepping mechanism and general layout were used for operating the programming switches.

Other early satellite data recorder designs A somewhat similar unit was developed in the early 1960s by the Raymond Engineering Company in Middletown, Connecti­cut, under contract from JPL. It had many similarities with the SUI recorder—it also operated entirely in the digital domain, with the tape advancing one physical step only when an input pulse was applied. The Raymond device, however, being produced later than the Iowa design, was able to use a superior configuration. Although its tape was also held in tension by a spring, the spring applied a torque to the tape take-up spool rather than the supply spool, and the tape was pulled forward by the spring when it was incrementally released by an escapement mechanism similar to that found in mechanical clocks. The Negator spring used in their design provided a nearly constant torque. An electric motor drove the tape in the other direction at a nearly constant speed to read out the data upon command.

The tape in the Raymond device moved 0.005 inch for each step, the same as in the SUI recorder. With a much longer tape, it had a total capacity of 100,000 bits versus 8000 in mine. That made it substantially larger, 2.25 by 4 by 5 inches, and heavier. Its power consumption was comparable to that of the SUI recorder. Developed to permit individual instruments aboard future multi-instrument spacecraft to have their own data storage, its use was overtaken by two developments. First, the rocket launching capacity increased rapidly after the initial space launches, so that extreme weight minimization was less important. Second, demands for data storage and transmission increased dramatically as the instruments became more discriminating, and the Raymond design did not meet that need.

Only a breadboard model of the Raymond recorder was built for testing, and it was never used in flight.30

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A completely different type of space tape recorder was launched into orbit on 17 February 1959 as a part of the Vanguard II instrument package. That recorder, de­signed by a group under William Stroud’s leadership at the U. S. Army Signal Corps Engineering Laboratories at Fort Monmouth, New Jersey, was designed to record cloud cover distribution over the daylight portion of the satellite orbit. It was a minia­turized version of more conventional analog recorders, with a weight of a pound or so. It used a 75 foot length of tape in an endless loop that did not require rewind­ing and had recording and playback times of 50 minutes and 1 minute, respectively. The recorder operated properly in orbit. Interpretation of the data was not possible, however, because of the unanticipated complex rotation of the satellite.

As mentioned earlier, the Soviets included a much larger data recorder in Sputnik 3, launched on 15 May 1958. However, that recorder failed before the launch. Political considerations caused them to launch without the delay that would have been required to fix the problem. Thus, they were deprived of the continuous data coverage that they wanted.

Explorer III tape recorder summary The Explorer III tape recorder set new stan­dards in terms of size, weight, required electrical power, and ruggedness. Some of the recorder’s most notable features were as follows:

• The final model was only 2.5 inches in diameter, less than 3 inches long, and weighed just over eight ounces.

• Its average power consumption was only 0.035 watts. That low power require­ment was a major factor in permitting the full Explorer III instrument to operate in orbit for 44 days.

• It was fully digital in its operation, making it relatively insensitive to temperature, battery voltage, and other variables. The fact that the tape was motionless most of the time contributed to the low power demand.

• All moving mechanical components except for the playback solenoid were dy­namically balanced, making it largely insensitive to vibration and various trans­lational and rotational motions of the satellite.

• All mechanical components were physically constrained so that high acceleration and shock in any direction could not damage the recorder.

• Ball bearings held friction to a minimum. Nineteen of them supported all rotating components and served as cam followers. The smallest ball bearing was only 5/32 (0.156) inch in outside diameter.

The tape recorder required more than 2000 hours of precision tooling in the Physics Department instrument shop over a one and a half year period. Edward (Ed) Freund worked with me as the principal instrument maker.31 He was helped at times by shop manager Joseph George Sentinella and fellow instrument makers Robert (Bob)

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Markee and Robert (Bob) Russell. For their work on the data recorder, the four were recognized in 1959 with Certificates of Recognition from the American Society of Tool Engineers.

I kept a spare recorder in my possession from the time of my departure from Iowa City in 1960 until early 1968. That year, I offered it to the Smithsonian Institution’s National Air and Space Museum, and arrangements were made with Frederick C. Durant III to transfer it to their care. In due course, it was cleaned and restored to fully operating condition by Ed Freund. In September 1968, I carried it to Washington and handed it to Fred. The official transfer to the museum was by a letter from Van Allen.32

The unit was identical to the ones launched in Explorer II (launch failure) and Explorer III, except that its relatively short-lived magnesium coating was replaced with gold plating to make it more immune to long-term oxidation.

Although the device included a number of unique and remarkable features, the Uni­versity of Iowa business office decided not to apply for patents. They concluded that there would not be enough demand for similar devices to make patenting economically attractive.

The staffs at ABMA in Huntsville and JPL in Pasadena did not wait idly for the final Washington approval—the initial Sputnik launch was their call to action. General Medaris took an audacious step only a few days after the launch by instructing von Braun and his organization to take Jupiter C, Missile 29 out of storage and begin preparing it for use. Although the general lacked authority for that action, the amount of money was small, and he figured that he could hide it if necessary. He was absolutely convinced that the Vanguard effort would run into trouble.7

Thus, von Braun and Pickering’s people began implementing the plans on which they had been quietly working. Although the tank of Missile 29 had been elongated earlier to hold more fuel and oxidizer to increase its performance, and although the engine had already been test fired with the new hydyne fuel in October 1956, many other changes were required. The vehicle had to be fitted with an attitude control system that would reorient it during the coasting period following first stage burnout,

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so that the cluster of upper stages would be horizontal when it reached the highest point in its trajectory. The apex predictor that Stuhlinger had built had to be integrated into the launch operations procedures so that it could be used in firing the second stage at just the right moment.

Both ABMA and JPL intensified their studies of the dynamics of injecting a satellite into orbit, maintenance of a durable orbit, satellite temperature control, and other technical factors. Most importantly, they began to tie the numerous studies, hardware, and software efforts together to produce a system that would operate effectively as a whole.

The Vanguard program had its first success with the launch of their spherical test satellite. Vanguard I, launched on 17 March 1958, being 6.44 inches in diameter as seen in Figure 10.5, became referred to in some of the press reports as the “grapefruit” satellite.

That satellite, however, even without any internal active scientific instruments, achieved a list of notable firsts. To start with, its high orbit (initial perigee of 406 miles and apogee of 2,421 miles) resulted in a very long orbital lifetime. The current estimate is that it will not reenter the Earth’s atmosphere for at least 2000 years. It represents the first use of solar cells for power generation in space. Another major technical achievement was the validation of the thermal design that had been worked out for the larger Vanguard satellites that followed.

Precision tracking of Vanguard I over an extended period by NRL and the Smithsonian Astrophysical Observatory resulted in the discovery that the Earth is not a spherical globe somewhat flattened at the poles, as previously thought, but is

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pear shaped. It also revealed variations in atmospheric density related to the rotation of the Sun and that the density of the upper atmosphere is far greater than formerly supposed.

As mentioned in Chapter 10, the full interrogation log shows that many of the early Explorer III interrogation attempts of the onboard tape recorder either did not elicit observable responses from the satellite or usable ground station recordings were not obtained. During the first hours, both Van Allen and I eagerly sought information on the performance of the newly orbiting instrument, especially its onboard data recorder. As Van Allen was returning to Iowa City the evening of the launch, he called John Mengel at NRL during a plane change in Chicago.21 He learned of the interrogation success history up to that point, that is, of the passes over Antigua (immediate post­launch check—good response), San Diego (no response), Quito (not heard—response possibly heard at Lima but not recorded), and Antofagasta (no response). Thus, by that evening, there were only two indications of possibly successful interrogations. Only one of them was from the instrument after it had spent some time in orbit, and that response was uncertain.

I was en route from the Cape to Huntsville, Alabama, during that first evening and not able to find out about any successful postinjection interrogations until nearly midday the next day, when I was finally able to talk to Mengel in Washington. By then, additional at least partly successful interrogations (commands followed by an audible response) had been achieved from Quito, Santiago (two passes), Antofagasta, Quito (observed at Lima), and Havana. During that same period, five other passes elicited no response.22

The first interrogation that resulted in the receipt of a strong signal carrying a complete data dump (that is, of an onboard recording covering a complete orbit of the satellite), and that was successfully recorded on the ground, was finally achieved at about 21:00 UT (6:00 PM EST) on 27 March at Quito, over 27 hours after launch! A few more interrogations of variable quality were obtained during the next nine hours by South American stations. Before any of those recordings could be displayed in human-readable form, however, they had to make their way from South America, through customs, to the NRL Processing Center in Washington, D. C.

Within the next few days, the situation began to show substantial improvement. On Friday, 28 March, successful playbacks were recorded at Santiago (2), Antofagasta, Lima, Fort Stewart (2), San Diego, and Quito. During that same time, there were failures on only three attempts.

Enigmatically, the San Diego station operator reported, based on their listening to the audible playback signal while recording their 28 March pass, that there was a possible data dropout of three seconds about halfway through the roughly six second data readout. The data at the time of the gap had been recorded on the satellite when it was near its highest position in orbit. That suggestion of an apparent zero counting rate became tremendously important as events unfolded.

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On Saturday, additional successful recordings were made at Santiago (2), Lima, Antigua, Havana, Fort Stewart, and San Diego, with three other failures. By that time, the first ground station recordings of the data playbacks were just arriving at the processing center in Washington, D. C.

I reached Iowa City from Huntsville in mid-morning that Saturday. Driving imme­diately to the physics building, I checked with Van Allen, Carl McIlwain, and Ernie Ray on their progress with the Explorer I data. Eight weeks had elapsed since that satellite had been launched. Significant quantities of its data had arrived and were being examined. Although there was a growing feeling that Explorer I was detecting some unexpected real physical phenomenon, we had not yet concluded that we were seeing a high radiation intensity.

During that weekend meeting, in addition to the discussion of the Explorer I data, I briefed the group on the results of the Friday meeting at Huntsville. I had planned on putting two GM counters with different amounts of shielding in our IGY Heavy Payload instrument. But Van was hesitant about that, expressing his opinion that two GM counters would increase the chances for instrument failure.23 Although he insisted during that discussion on making one of the two counters a dummy, after we realized later that the Explorer I and III instruments were detecting high-intensity radiation of a largely unknown character, a live second counter was reinstated with added absorber material to help us in further understanding the new phenomenon.24

Also during that Saturday meeting, Van Allen and I agreed that I needed to move back to Iowa City as quickly as possible. We settled on a date of 6 April (only eight days thence) for my switch back to the SUI payroll. My family would return as quickly as we could settle our affairs in Pasadena.

I returned to my office in Pasadena on Monday for a week of whirlwind activities to wrap up my work there and prepare for our move.

Iowa’s role in the burgeoning space program was gaining wide publicity. On Sunday, 30 March, a CBS television camera crew arrived on the Iowa campus and began setting up their equipment. Walter Cronkite interviewed Van Allen on Monday (Figure 12.1), and his crew continued taping additional footage the next day.

Significantly, during that interview, Van Allen still made no mention of the pos­sibility of a region of unexpectedly high radiation intensity. The Explorer III data had not yet been examined, and he was, as was his usual practice, being careful to avoid premature speculation. Even later, on 20 April, when that interview was aired, no public mention was made of the discovery, even though, by that time, we were gaining an increased understanding of what our instrument was seeing, and a meeting had already been arranged in Washington for us to disclose our new findings.

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Even while the interview was being taped in Iowa City, the first Explorer III tapes arrived in Washington from several of the Minitrack ground stations. H. J. (Jack) Peake, the NRL engineer in charge of processing our data there, reported upon the arrival of those tapes in a short letter, as reproduced here.25

Van Allen’s First Lookat the Explorer III Data The day after his Cronkite interview, Van Allen went again to Washington to discuss a number of Explorer I and III matters. On Wednesday, 2 April, he took a taxi from his downtown hotel to the NRL facility in the southern corner of the District, where he conferred with Joseph Siry (relative to orbital data), John Mengel (data acquisition and data processing), and others of the Vanguard team.26

This is a good place to reemphasize the fact that NRL’s Vanguard staff provided outstanding support for the early Explorer program. Their Vanguard I had been launched just two weeks before the Explorer III launch, and after that launch, they were working around the clock to deal with tracking, orbit determination, data acquisition, and data processing simultaneously for three satellites.

As he concluded his business at the NRL, Van Allen took a taxi to the Vanguard Computing Center at 615 Pennsylvania Avenue. There he received a copy of Jack Peake’s letter and the film that had been prepared the previous day27:

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1 April 1958

To: Van Allen and Ludwig

Received from Minitrack stations at San Diego and Ft. Stewart, Ga. 4 1958 gamma recordings (2 from each station) yesterday. One record, San Diego at 1748 Z [UT] on 28 March, was of such high S/N [signal-to-noise] ratio that we transcribed it to the enclosed film record. On the film is pulse time code (1748 Z is marked on the film), detected signal, and 10 kc (needs some magnification to see peaks clearly).

Please accept the film record, compliments of the U. S. Navy! Will be sending along 1/4-inch tape transcriptions shortly.

Sincerely,

H. J. Peake Code 6413 Applications Branch Solid State Division

Putting that precious first Explorer III data readout into his briefcase, he returned to his DuPont Plaza Hotel room, stopping en route at a Peoples Drug Store to pick up chart paper and a few drawing supplies. Late into the night, Van read the data from substantial portions of the record, roughly computed the pulse rates with his slide rule, and plotted the data on a graph. He then charted the counting rate as a function of time. He completed it at about 3:00 in the morning, packed his work sheets and graph into his briefcase, and retired for the rest of the night.

He later recounted that, at that point, he was convinced “that our instruments on both Explorers I and III were working properly, but that we were encountering a mysterious physical effect of a real nature.”28

Although the original film from which he worked that night was apparently not preserved, his original notes and the resulting graph do exist in the University of Iowa Libraries, Department of Special Collections.29 Figure 12.2 is a reproduction of a portion of that graph.

Back in Iowa City Jack Peake also shipped copies of his 1 April letter and the strip- film recording of the San Diego data readout to Iowa City. Carl McIlwain recalled that he met a delivery person early in the afternoon, almost certainly on 2 April, at the entrance of the old Physics and Mathematics Building. Excitedly, he took the film to the basement, where he, Ernie Ray, Joe Kasper, and Herbert (Herb) Sauer quickly mounted it on a reel-to-reel microfilm reader. Carl had been saying for over a month that the transition from normal cosmic ray rates to zero counts was the key to whether it was from an instrument failure or high radiation fluxes. Quoting Carl, “and there it was!”30 Smooth transitions in the counting rate were instantly apparent.

At that point, Carl stopped looking at the film to pursue the then-paramount question. If high radiation intensities were actually being encountered, what would account for the apparent zero counting rates? He quickly lashed together a set of

equipment, using a GM counter and coupling circuit similar to those in the satellite instrument. Setting the counter in front of the X-ray machine that he had been using for his rocket instrument calibrations, he made a quick set of runs. Lo and behold, initially the pulse rate at the output of the coupling circuit rose as expected with increasing X-ray intensity, but it then fell off at higher exposure levels! At rates that should have been about 30,000 per second, the rate actually observed at the output of the circuitry was zero.

That behavior resulted from the characteristics of the GM counter and its coupling and scaling circuits. When an ionizing particle entered the counter and interacted with its internal gas, it produced a pulse on the counter’s central anode. That pulse took only a few microseconds to build. It decayed, however, at a much slower rate, depending on the resistance and capacitance in the circuit. At normal primary cosmic ray rates, the relatively leisurely decay was essentially complete by the time another particle arrived. Thus, all of the arriving particles produced pulses of full amplitude that were counted by the scaler circuits.

When two events occurred much closer together, however, the pulse for the second event started, not from a zero value, but from a higher value that still lingered from the previous event. The transition was from that higher value to, still, the fixed power supply voltage. Thus, the amplitude of the second pulse at the input

FIGURE 12.3 The note that Ernie Ray left on Van Allen’s door after Ernie and Carl Mcll – wain saw the results of Carl’s exposure of the GM counter to an X-ray beam. The note was scrawled on a sheet of paper that was used either earlier or later for some extrane­ous doodling. The exact date of the note is uncertain—the date at the top in Van Allen’s handwriting (5 April) could be the date that he filed it, not necessarily the date that he first saw it. The annotation at the bottom (3 April) is probably the date of the doodling, not necessarily the date of the note. This au­thor’s best judgment is that the note was written on either 2 or 3 April. (Courtesy of the University Archives, Papers of James A. Van Allen, Department of Special Collections, University of Iowa Libraries.)

to the scaler circuit was less than its full normal value. As the GM counter pulses became closer and closer together, the pulse amplitudes at the scaler input became smaller and smaller. Eventually, the pulse amplitudes became too small to trigger the scaler. When that happened, the scaler registered none of them, seeming to signify a zero rate.

Bolstering the tentative conclusion With that information, Ernie excitedly wrote his famous “Space is Radioactive” note (reproduced here as Figure 12.3) and posted it on Van Allen’s door.31 Although, of course, Ernie and Carl knew that space was not radioactive in the true sense of the word, the note clearly expressed their excitement and firm belief that the instrument was, in fact, encountering a real very high radiation level.

Van Allen returned from Washington to the Iowa campus sometime on 3 April. He met, either late that day or the next day, with Ernie and Carl to show his data plot. Carl then offered his data showing the GM counting rate during its exposure to the X-ray beam. The three, Van Allen, Ernie, and Carl, were immediately convinced that the only possible interpretation of the data was that Explorers I and III were encountering very high fluxes of radiation—radiation at least a thousand times as intense as the normal cosmic ray rate.

They quickly set about to make a more complete and detailed plot of the 28 March San Diego data. On Friday, 4 April, Ernie, representing his coworkers, penciled a

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second note to Van Allen that accompanied their data plot. Its first page read, “An analysis of data from 1958/. San Diego interrogates: 28 March 1948 Z.” Its second page read32:

From the preliminary information from Vanguard computing center, perigee occurs five minutes after the maximum latitude. Evidently interrogation also occurs near perigee. Thus the data show low (reasonable) counting rates near perigee. The interesting portion of the graph has equatorial crossings and apogee in it.

Evidently there is no hole in space. Rather, space is radioactive.

Very rough preliminary work with an Anton Geiger tube indicates that it stops putting out usable pulses when, if its dead time were zero, it would be counting 104-106/sec.

Data read and analyzed and supporting work carried out courtesy of Kasper, Mcllwain, Sauer, and Ray.

[Signed] Ernie Ray 4 April 1958

The first generation of spacecraft consisted of relatively simple payloads in which simplicity, reliability, and, in the United States, suitability for small launch rocket weight-lifting capabilities took precedence. Those spacecraft carried a single primary

395

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scientific instrument, plus, in some cases, one or a few secondary instruments and engineering sensors. Sputnik 1, Explorers I through V, Vanguards I and II, and Pioneers 3 and 4 were clearly in this category.

Vanguard II The Vanguard program continued to move forward. After some addi­tional disappointing launch failures, a successful launch on 17 February 1959 placed 21 pound Vanguard II into a durable orbit. It contained a single active scientific in­strument array—a pair of optical cloud cover scanners provided by the U. S. Army Signal Corps Research and Development Laboratory at Monmouth, New Jersey, un­der William (Bill) G. Stroud’s leadership. It depended on the satellite’s spin as it advanced in its orbit to trace a raster pattern that could be processed to provide a pic­ture of the Earth. Although the instrument operated perfectly throughout its operating lifetime, its success was marred by the fact that the satellite was nudged following separation from its third rocket stage, causing the satellite to wobble. Thus, the cloud cover instrument traced a much more complex path over the Earth’s surface, making it next to impossible to assemble coherent pictures.

Vanguard II also supported a secondary objective. Its clean, spherical shape, com­bined with the Vanguard tracking and orbit determination capabilities, permitted accurate measurements of satellite drag and therefore upper atmospheric density as a function of altitude, latitude, season, and solar activity. Among other things, Vanguard II showed that atmospheric pressures, and thus drag and orbital decay, were higher than anticipated in the region where the Earth’s upper atmosphere gradually fades into space.

SCORE The SCORE project initiated the field of satellite radio communications. The acronym stood for Signal Communication by Orbiting Relay Equipment. It was a program supported by the Advanced Research Projects Agency, with the payload supplied by the U. S. Army Research and Development Laboratory at Fort Monmouth, New Jersey. The payload consisted of a communications repeater, augmented by an onboard tape recorder that was capable of recording and delayed playback of voice messages. Launched on 18 December 1958, it broadcast the famous “Christmas mes­sage” by U. S. President Dwight D. Eisenhower. With an operating lifetime of 12 days, the communications objectives were completely met, including the demonstration of both real-time and delayed transmission from one ground station to another.

Probably more significantly, it met a major U. S. geopolitical objective. Launched only 19 days after the first fully successful test flight of an Atlas ICBM, and result­ing in the placement of the complete 8700 pound Atlas main stage and its payload in orbit, it represented an impressive new U. S. launch capability. Although billed as a peaceful scientific mission, SCORE demonstrated for the entire world that the United States was also finally capable of delivering nuclear payloads anywhere on Earth.

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The similarities between the SCORE and the earlier USSR Sputnik 1 achievements are striking. Sputnik 1 was launched only 44 days after the Soviets achieved their first fully successful test flight of an ICBM. Its declared scientific objective was, also, communications. But its main purpose was to demonstrate to the world a long-range strategic rocket launching capability. Thus, the two projects had similar objectives, and both placed impressive weights in orbit—over 14,000 pounds (rocket plus detached payload) for Sputnik and 8700 pounds (rocket plus integrated payload) for SCORE. In terms of implied nuclear capabilities, the two were about equal. The U. S. nuclear devices were physically smaller and lighter than their USSR counterparts, and could, therefore, be launched with smaller launch vehicles.

The main distinction between the two programs was that the Soviets were able to demonstrate their capability fully 14 months before the United States was able to do so.

The race to the Moon As soon as the first satellite was launched, mankind’s ev­erlasting fascination with the Moon kicked in. In the thoughts of some, orbiting the Earth was only a prelude to the much more exciting prospect of flight to the Moon. Both the Soviets and the Americans quickly set their sights on that goal.

Lunar missions introduced a new set of technical challenges. Not only must the rockets push the spacecraft to an initial speed of about 18,000 miles per hour to get them into Earth orbit, but they must speed beyond that to an initial velocity of about 25,000 miles per hour to escape most of the Earth’s gravitational pull and reach the neighborhood of the Moon. In addition, they require far more accuracy in initial aiming and in on-course trajectory control. Communication and tracking also presented new challenges because of the much greater transmission distances.

Information about first Soviet attempts at flights to the Moon is sparse because of their initial practice of outright denial of unsuccessful attempts. Information published in later years indicates that the Soviet program for lunar flights was actually formally approved as early as March 1958. Although the Miami Herald reported on 4 August 1958 that the Soviets had tried and failed to launch a rocket to the moon on 1 May,1 no other evidence can be found that they attempted a deep space launch that early. The first substantiated Moon attempt was made by the Soviets on 25 June 1958 with an SL-3 (A-1) rocket (derived from the SL-1 [A] rocket that had launched the first three Sputniks). That attempt failed.2

The U. S. Thor-Able 1 mission (sometimes referred to as Pioneer 0) was launched on 17 August 1958. The vehicle was a Thor Intermediate-Range Ballistic Missile, topped by a modified Vanguard third-stage solid rocket. On that attempt, the first-stage rocket exploded 77 seconds after liftoff, probably due to a failed turbopump bearing.

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I was at Cape Canaveral preparing for our Explorer V launch at that time and witnessed the Thor-Able attempt. My journal reads:

Well, the moon attempt was a failure. After 77 seconds it blew. I saw it from Hangar S, five miles away, Bill Whelpley from one half mile (RIG [Radio Inertial Guidance] site). Bill said after it climbed 300 or 400 feet, a small fireball appeared for three seconds about the diameter of the second stage, at the point where stages one and two join. I didn’t see this from Hangar S, and to me it appeared to climb normally until 77 seconds, when two white puffs of smoke were seen in quick succession. Following the first one, several small pieces were thrown off.

It looked like it might have been an engine explosion.

The beaches were lined for the shot. It is surely a shame it failed, because now USSR will have another chance to beat us.3

The instrument complement on this 83 pound payload consisted of a nonlinear search coil magnetometer provided by the Space Technology Laboratories Inc. (STL) to measure the Earth’s magnetic field and determine whether the Moon had such a field. The STL also provided a microphone assembly to detect micrometeorites. The Naval Ordinance Test Station provided an image-scanning infrared television system to take low-resolution images as the craft approached the Moon.

Thor-Able 1 marked the entry of an important new organization on the U. S. space scene. In September 1953, Simon Ramo and Dean Wooldridge had formed the Ramo-Wooldridge Corporation to work directly with the U. S. Air Force on problems of system engineering, including development of the Atlas Intercontinental Ballistic Missile (ICBM). Adolf (Dolf) Thiel, one of the original group of German rocket experts brought to the United States following World War II, joined them in 1955. The Ramo-Wooldridge Corporation was renamed STL in December 1958. That orga­nization (later spun off to form Thompson Ramo Wooldridge and, later still, simply TRW) was responsible for a long string of space missions during the 1950s, 1960s, and 1970s, of which Thor-Able 1 was the first. TRW has remained a prolific contractor for NASA and military space efforts.

The Soviets followed with another failed attempt on 23 September. That Luna 1958A launch vehicle structure failed after 92 seconds of flight, and the vehicle exploded. It is believed that that spacecraft weighed about 800 pounds and carried an instrument complement somewhat like the later successful Luna 1.4

The United States achieved a modest space first by sending a craft well beyond low Earth orbit for the first time. Under the banner of the newly formed NASA, the Air Force launched Pioneer 1 on 11 October 1958, again with their Thor-Able launcher (Figure 14.1). Although Pioneer 1 failed to achieve its primary objective of reaching the Moon due to a programming error in the upper stage, it did travel out to a distance of about 70,000 miles from the Earth.

Pioneer 1 looked much like the earlier Pioneer 0, except for the addition of one new instrument. Time had permitted the development and addition of a chamber to measure total ionization as the probe moved through the radiation zone.

The ionization chamber experiment was a cooperative effort between scientists at STL and Carl McIlwain at Iowa. The STL experimenters, Alan (Al) Rosen, Charles (Chuck) P. Sonett, and Paul J. Coleman Jr., carried the primary responsibility for preparing the instrument, while Carl specified the characteristics of the chamber and participated in its preparation, calibration, and data interpretation.

The chamber, produced by Nicholas Anton and his engineers at the Anton Elec­tronics Laboratories under Carl’s guidance, consisted of an aluminum-walled vessel with a volume of about 2.5 cubic inches. It was initially filled with pure argon to a pressure of about 193 pounds per square inch. The design of the electronics that followed the chamber was based on the circuit that Carl had developed for the scintillation counters in Explorers IV and V Its most noteworthy feature was a log­arithmic response that provided measurements over a huge dynamic range so that it could determine the radiation dosage both in the midst of, and outside, the radiation zone.

The chambers were carefully calibrated before launch with a Cobalt-60 radioactive source at the Radiology Department of the University of California, Los Angeles

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Medical Center. It was determined later, however, that the Pioneer 1 flight chamber had had a slow leak, and that by the time of the flight, the pressure had dropped to about 22 pounds per square inch, with a concomitant reduction in its sensitivity. A correction for that change, as well as corrections for other instrumental errors and temperature effects, was used for all work on the data.

For the first 17 minutes of the Pioneer 1 flight, the telemetering system was dedicated to monitoring vehicle performance. Then the scientific instruments were turned on so that useful research data began when the spacecraft was about 2200 miles from the Earth’s surface, and at about 32 degrees north latitude and 30 degrees west longitude. Data recovery continued until the spacecraft reached about 22,400 miles height at about 6 degrees north latitude and 0 degrees longitude. Unfortunately, scientific data were not recovered during the rest of the flight, including the return trajectory.

Analysis of the Pioneer 1 ion chamber data provided several significant results. (1) It verified by direct measurement the extent of the region of high-intensity radiation that had been inferred earlier from the lower-altitude Explorer I, III, and IV data. (2) Throughout the altitude range from about 2500 miles to 15,000 miles from the Earth’s surface (to 4.8 Earth radii from the Earth’s center), the level of ionizing radiation remained in excess of two roentgens per hour. (3) When the spacecraft was outward bound at about 20 degrees north latitude, peaks of the radiation belt intensity occurred at heights of about 6600 and 7400 miles (2.6 and 3.4 Earth radii from the Earth center). The maximum level of radiation at those locations was about 10 roentgens per hour. Results from later flights showed that the second peak was accurately correlated with the center of the outer radiation belt.5

The Soviets tried again with Luna B on 12 October 1958, just a few hours after the Pioneer 1 launch. Although details of its payload are also not known, it is presumed that it was essentially the same as Luna 1958A. The rocket exploded 104 seconds into the flight.

The United States tried again on 8 November with Pioneer 2, a craft that was gen­erally similar to Pioneer 1, but with the addition of a proportional counter telescope by John Simpson’s group at the University of Chicago. Another rocket failure—the third stage separated from the second and failed to ignite, and the spacecraft fell back to Earth over northwest Africa. Carl McIlwain’s ion chamber did, however, provide useful information. Correlation with the Explorer IV data showed that the counting rate at about 1000 miles height was relatively independent of longitude, but strongly dependent on geomagnetic latitude, thus supporting the model of the trapping region that had evolved by that time. In addition, use of the ion chamber data and the data from the proportional counter telescope showed that the trapped

particles were a combination of electrons and protons, rather than high-energy elec­trons alone.

And another try by the Soviets on 4 December: Luna C. The payload, too, is presumed to have been a copy of Lunas A and B. The rocket exploded after 245 seconds of flight.

A very productive partial success was finally achieved two days later with the NASA – Army launch of 13 pound Pioneer 3 on 6 December 1958. It was the first attempt with the Juno II launch vehicle developed by the Huntsville group. That vehicle substituted a larger Jupiter rocket for the Redstone booster that had been used in the earlier Jupiter C-Juno I configuration for Explorers I, II, III, IV, and V

The form of the payload was a cone attached to a short cylindrical section, with an overall height of about 24 inches and a cylinder diameter of about 10 inches, as seen in Figure 14.2. It was developed primarily by the Jet Propulsion Laboratory (JPL) with two main objectives. One was to demonstrate a close flyby of the Moon. Two

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photocells were set to trigger by the light of the Moon when the probe was about 20,000 miles distant, to serve as tangible proof of the accomplishment.

The second objective was to make radiation measurements throughout the flight to further substantiate and map the newly discovered high-intensity radiation around the Earth. Van Allen served as the principal investigator for that experiment, which employed a pair of Geiger-Miiller (GM) counters sized to measure the full intensity of the high-intensity radiation. He, aided by rising undergraduate student Louis (Lou) Frank, calibrated the payload’s detectors in the Iowa laboratory, using a variety of radiation sources, as shown in Figure 14.2.

That attempt with the new launcher also failed to reach the Moon. Early depletion of propellant caused the first-stage engine to shut down 3.7 seconds early. Although that prevented the vehicle from reaching escape velocity, the craft did climb to a height of over 66,000 miles before falling back to Earth.

Although the flight fell short of its first objective, it met the second one splendidly. In fact, its failure to reach escape velocity, with the instrument falling back to Earth, provided a second pass through the region of high-intensity radiation. While the outbound trajectory passed through the heart of what came to be referred to as the outer belt, it only grazed the core of the inner belt. But the return trajectory passed through the central cores of both belts and proved beyond any possible doubt the presence of two distinctly different regions, as seen later in Figure 14.4.6

The two GM counters in Pioneer 3 had distinctly different characteristics. The first was an Anton type 302 counter similar to the one used in Explorer IV It was followed by a very wide dynamic range scaler and filter arrangement first suggested by this author in April 1958.7 Although the Explorer IV schedule had been too tight for me to develop that circuit at the time, JPL engineers developed it for Pioneers 3 and 4. It had the feature that multiple scaling factors of 512, 8192, and 131,072 could be telemetered over a single channel.8 That wide dynamic range permitted the instrument to track a variation of over 2000 to 1 in counting rate during its transit through the region of high-intensity radiation.

The second GM counter was a much smaller one, specially built for this mission by the Anton Electronic Laboratories as their type 213. Its effective size was about one-tenth that of the 302 counter, and its primary purpose in Pioneer 3 was to serve as an ambiguity resolver for the 302 counter.

The Soviets finally approached the Moon on 2 January 1959 in spectacular fashion. Using a redesigned R-7 launch vehicle, their spacecraft (variously referred to as the First Cosmic Rocket, Mechta, Dream, Luna 1, or Lunik 1) was intended to impact the Moon, although that was not admitted by the Soviets until much later. A malfunction in the ground-based control system caused an error in the rocket’s

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burn time. Although missing its primary objective, it passed within 3700 miles of the Moon’s surface and became the first man-made object to escape from Earth orbit to take up its own orbit around the Sun. That orbit lies between the orbits of Earth and Mars, where, barring collision with some other object, it will dwell for the ages to come.

Luna 1, weighing nearly 800 pounds, carried an impressive array of instruments. They included GM counters, scintillation counters, a Cerenkov detector, a magne­tometer, a micrometeorite detector, and traps for detecting low energy protons. The data provided new information on the Earth’s trapped radiation, showed that the Moon did not have a substantial magnetic field, and made the first direct observations and measurements of the solar wind, a strong flow of ionized plasma emanating from the Sun.

While outbound, at a distance of about 74,000 miles from the Earth, the spacecraft released a cloud of sodium gas, creating an orange vapor trail. That cloud was easily visible from the neighborhood of the Indian Ocean, and accomplished two purposes. It provided a visible confirmation of the vehicle’s trajectory and served as an experiment on the behavior of gas in the vacuum of outer space.

The spacecraft also contained a number of medallions for dispersal around the point of intended lunar impact to perpetually mark the feat.

The U. S. Pioneer 4, launched on 3 March 1959, followed Luna 1 to the general neighborhood of the Moon. It passed about 37,000 miles from the Moon and entered its own independent orbit around the Sun. The records generally refer to it as a successful mission, even if it did not pass close enough to the Moon to trigger its photoelectric sensor. The significance of the accomplishment suffered somewhat by being greatly overshadowed by the Luna 1 flight two months earlier. The Pioneer 4 spacecraft weighed only one-sixtieth the weight of Luna 1 and passed the Moon at about 10 times the distance.

The Pioneer 4 spacecraft was similar to Pioneer 3—its only difference was the inclusion of additional shielding around the type 213 GM counter to provide bet­ter information about the penetrating ability of the charged particles. Van Allen’s set of objectives for that flight included a resurvey of the intensity structure of the Earth’s radiation zones, an examination of temporal changes that might have oc­curred since the Pioneer 3 flight, a rough further determination of the composition and spectral character of the radiation, and a look in interplanetary space for re­gions of plasma that might contain particles energetic enough to trigger the GM counters.

One important additional contribution of the Pioneer flights was to shake down and quantify the performance of the Microlock tracking and telemetry system developed

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by JPL. That system, using the 85 foot antenna dish at Goldstone Lake in California, turned out to be capable of recovering the signal from the miniscule transmitter on the 13 pound Pioneer 4 to a distance of over 400,000 miles. Even there, transmission apparently stopped only because of the expected exhaustion of the probe’s batteries. That telemetry system was a precursor to the wonderful capability that JPL has steadily improved and used over the years for tracking and recovering the data from a long progression of deep space excursions.

The Pioneer 4 scientific productivity was marred slightly by two factors. The largest of the three scaling factor taps for the 302 GM counter was lost due, apparently, to a major physical shock during the burning of one of the rockets. The performance of the other two taps was normal. Second, telemetry data were lost for about half a minute, just as the probe was passing through the core of the outer radiation zone, that is, between about 2.5 and 4.5 Earth radii.

The Soviets made another attempt to impact the Moon on 18 June 1959, but the vehicle’s guidance system failed.

Finally, following a 12 September launch, the Soviets succeeded in making the first physical contact with the Moon. After a 33.5 hour flight, Luna 2 impacted at a point west of Mare Serenitatis. To mark the event, two small spheres with their surfaces covered with stainless steel pentagonal elements were ejected and exploded shortly before spacecraft impact, to disperse the pendants around the impact site. The pendants were emblazoned with the USSR Coat of Arms and the Cyrillic letters CCCP. Some 30 minutes after the spacecraft impacted, the third rocket stage also struck the Moon. Another device on that rocket—a capsule filled with liquid and with suitably engraved aluminum strips—marked its impact site.

Luna 2, shown in Figure 14.3, weighed an impressive 860 pounds. It included six GM counters, three scintillation counters, two Cerenkov detectors, a magnetometer, micrometeorite detectors, four low-energy ion traps, and the equipment for generating a sodium cloud. As in the case of Luna 1, a bright orange sodium cloud was produced en route.

Several of the scientific instruments were reconfigured from the Luna 1 arrange­ment to take advantage of new scientific information then accumulating. The three – axis fluxgate magnetometer’s dynamic range was adjusted to provide greater measure­ment accuracy as it approached the Moon. Counter sizes and shielding were adjusted. The ion traps were arranged in a different configuration.

Luna 2 provided a wealth of new information on the particles and fields around the Earth, in interplanetary space, and near the Moon.9 One of its most notable achievements was the confirmation and further delineation of the solar wind by the ion traps designed by Konstantin Gringauz. Its magnetometer placed a very low limit on

the strength of the magnetic field near the lunar surface—it is essentially nonexistent. The radiation detectors confirmed the broad structure of the outer radiation belt, as it had been revealed by Pioneer 3. The diversity of detectors added valuable new information about the composition of the outer belt.

On 4 October 1959, the second anniversary of their first Sputnik launch, the Soviets achieved another spectacular first with Luna 3. It took the first pictures of the back side of the Moon.

The Luna 3 craft employed a completely new design. In addition to its primary moon-imaging instruments, it included scientific instruments for measuring cosmic rays, other charged particles, and micrometeorites. Unfortunately, very few results from those auxiliary instruments can be found—the pictures of the Moon’s far side completely dominated the postflight public and scientific releases. The fact that the flight did not contribute substantially to the early radiation belt studies is also likely due to its being launched over the North Pole, so its trajectory carried it north of most of the Earth’s radiation belt structure.

406

With the aggregation of data from Sputniks 2 and 3, Explorers I, III, IV, and 6, Lunas 1 and 2, and Pioneers 1,3, and 4, a quite clear picture of the Earth’s radiation belts was emerging. The collective set of lunar probes during the closing years of the 1950s was especially important in delineating the belts’ overall structure and composition. Figure 14.4 shows the approximate relationship between the trajectories of deep space probes Pioneers 1,3, and 4 and Lunas 1 and 2 and the locations of the two belts.

t has been more than fifty years since the opening of the Space Age with the launching of the first Soviet Sputnik on 4 October 1957.1 That new Earth satellite’s self-assured beep-beep-beep signaled the beginning of a new era. Much has happened since then, including the operation of numerous robotic instruments to probe the new frontier, man’s first tentative venture into Earth orbit, the brash human landing on the Moon, the introduction of new space technologies into our everyday lives and culture, and many new and oftentimes breathtakingly beautiful glimpses of our vast universe.

The years since Sputnik have crept by at a relentless pace. A substantial fraction of the world’s present population has been born since then, and most of them know of those early times only through oral tradition, written history, and artifacts in museums.

I was recently shocked by the realization that we are nearly as far into the Space Age now as we were into the Age of Aviation when the Space Age began. Fifty years before Sputnik (only a few years after the Wright brothers’ first flights in a powered aircraft), the pioneers of aviation were speculating on whether “aeroplanes” might possibly play a useful role in warfare, transportation, and commerce. By the end of those five decades, the effectiveness of aircraft in warfare had been well established in two world wars. Airlines had taken over from trains and ships for much of the long-distance passenger travel. Aircraft were handling a substantial portion of the long-distance shipment of goods. Turboprop engines were rapidly displacing piston engines, and jet engine-driven aircraft were well established in the military services and were beginning to come into commercial service.

During the second half of the twentieth century, spacecraft have been absorbed into our culture in much the same way. We depend on them for many facets of

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2 OPENING SPACE RESEARCH

our everyday lives, including communications, navigation, position finding, Earth observation, weather and climate observation, tactical and strategic reconnaissance, and many other capacities.

Enough time has elapsed since the beginning of the Space Age to gain a good historical perspective. But it is recent enough that the memories of still-living direct participants can be tapped.

It has been customary in the popular arena to describe entry into space primarily in terms of the manned program. This is perhaps understandable because the venture of humans into any new realm is always far more exciting than the introduction of mere robots.

Nevertheless, instrumented robots did enter space first, and many of the initial technical and operational problems were solved during their development and use. Fortunately, the voices of enthusiastic and dedicated scientists, reinforced by a some­times sporadic popular interest, ensured that the first flights of space-capable launchers were put to useful purposes for research rather than being used simply to prove the technology or for military purposes. This resulted in an immensely imaginative and productive program of scientific discovery.

This tale’s focus on the research program at the University of Iowa’s Department of Physics and Astronomy is not meant to minimize the work of other groups. It does reflect the fact, however, that the Iowa department, under Van Allen’s guidance, did provide outstanding leadership in the new branch of research.

The story may be of special interest from two points of view. First, it describes the experiences of a fledgling scientist-engineer in a uniquely exciting period of initial discovery, vigorous growth, and historical significance in a new scientific arena. Second, it uses many historical materials dealing with the details of the development, launch, and use of the early Explorer satellite instruments that have never been published and do not exist elsewhere.

By extreme good fortune—by being in just the right place at the right time with the appropriate background—I was able to participate actively in the opening of this new era. As I completed my undergraduate work and was looking forward to my graduate studies, I became increasingly aware of the significance of the time. In addition to my already established custom of recording work-related activities in laboratory notebooks, I started noting some of my thoughts and experiences in personal journals. Later, as more of my time was spent in management, I began a series of office journals. Much of the material for this book was derived from those three sources.

INTRODUCTION

he International Geophysical Year (IGY) was an epical scientific event. Through­out the community of geophysical researchers, it provided an infusion of funds and an integrating mechanism for hundreds of individual efforts that were made pos­sible by the rapidly evolving technologies of the time. The various coordination and sharing arrangements that were established for the IGY facilitated the interchange of data and information at a level far beyond that which would have occurred otherwise, and many of those arrangements have continued to the present day.

IGY inception and early planning

This IGY was not the first comparable international effort, although the scale of the new endeavor went far beyond that of previous ones. By the late nineteenth century, there had been a growing realization that the need for observations was global in nature, far beyond territorial boundaries, the intellectual resources of individuals, and even entire countries. This realization, coupled with the newly evolving technologies, was pushing the frontiers of human exploration over more and more of the Earth’s surface.

As a part of that expanding vision, two large-scale international efforts were mounted to apply the combined resources of the world’s leading scientists to exam­ine broad geophysical questions. The First International Polar Year, in 1882-1883, involved a collaboration of scientists to examine the geophysics of the Polar Regions, with concentration on the Arctic. That program included the establishment of a number of meteorological, magnetic, and auroral stations and their operation for about a year.

The Second International Polar Year was conducted during 1932-1933, the golden jubilee of the first. It repeated the earlier endeavor but extended its scope by adding ionospheric observations and by including a substantial component in the Antarctic.

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Those two collaborations provided some of the inspiration, and served as a model, for the International Geophysical Year—1957-1958. That third endeavor, marking the silver jubilee of the Second Polar Year, took place during the period 1 July 1957 through 31 December 1958.

Much has been published over the years to document the planning and achievements of the IGY.1,2’3’4’5’6 Thus, only a brief summary is provided here.

An informal and largely spontaneous dinner party at the Van Allen home in 1950 served as the springboard for the IGY. Van Allen and his family were living at that time in a rented house at 1105 Meurilee Lane, Silver Spring, Maryland, located just off Dennis Avenue near its intersection with Sligo Creek Parkway. This was just a 10 minute drive from Van Allen’s laboratory in downtown Silver Spring.

In addition to hosts James and Abigail (Abbie) Van Allen, that dinner party included Lloyd V. Berkner, Sydney Chapman, J. Wally Joyce, S. Fred Singer, Merle A. Tuve, and E. Harry Vestine. The story of that momentous dinner is best told in Van Allen’s own words:

Vestine [Harry Vestine, who had originally urged Van Allen to make the electrojet search] was delighted with our equatorial electrojet results, as was [Sydney] Chapman who was visiting the United States in early April 1950. On April 5, they visited APL in order to learn about the results at first hand. Chapman expressed an interest in getting together with us and with Lloyd Berkner and Wally Joyce for further discussions. I immediately called my wife to confirm a previously tentative plan that she would have the group for dinner at our home. During the day, she cleaned the house, prepared a splendid dinner, and managed to feed our two young daughters and tuck them into bed as the guests arrived.

The occasion turned out to be one of the most felicitous and inspiring that I have ever experienced. Berkner was one of the leading experts on ionospheric physics and telecommu­nications at that time, had been a member of the scientific staff of the first Byrd Antarctic Expedition in 1928-1930, and had extensive experience in international cooperation in sci­ence while a member of the U. S. State Department. Joyce was a distinguished geomagnetician who had published the well-known Manual of Geophysical Prospecting with the Magnetome­ter in 1937 and was, as I recall, on the staff of the National Research Council at this time.

The dinner conversation ranged widely over geophysics and especially geomagnetism and ionospheric physics. Following dinner, as we were all sipping brandy in the living room, Berkner turned to Chapman and said, “Sydney, don’t you think that it is about time for another international polar year?” Chapman immediately embraced the suggestion, remarking that he had been thinking along the same lines himself. The conversation was then directed to the scope of the enterprise and to practical considerations of how to contact leading individuals in a wide range of international organizations in order to enlist their support. The year 1957-1958, the 25th anniversary of the second polar year and one of anticipated maximum solar activity, was selected. By the close of the evening Chapman, Berkner, and Joyce had agreed on the strategy for proceeding.7

Van Allen’s wife Abbie had a slightly different recollection of the event. In a conversation with Tom Krimigis in July 2007 she related, “… she was talking with Chapman first thing after the dinner and he was waxing eloquently about the Inter­national Polar Year of 1932-33. She suggested, “isn’t it about time to have another one?” to which he responded, “Well, maybe we should.”8

CHAPTER 3 • THE INTERNATIONAL GEOPHYSICAL YEAR 69

Planning for this third international endeavor progressed steadily. In May 1950, some 20 scientists, including Chapman (who had by that time left Oxford University for the University of Alaska), further discussed the suggestion at a meeting at the Naval Ordnance Test Station (now Naval Air Weapons Station) near Inyokern, China Lake, California. Further discussions and conceptual planning occurred soon after that at a Conference on the Physics of the Ionosphere, hosted by the Ionospheric Laboratory of Pennsylvania State University.

A formal proposal based on those discussions was conveyed by Berkner and Chapman in July 1950 to the Joint Commission on the Ionosphere, an organization of the International Council of Scientific Unions (ICSU). During the rest of 1950,

1951, and much of 1952, the proposal wended its way through the various ICSU member organizations. In the process, the World Meteorological Organization was added to the list of supporting institutions. The program’s scope was expanded to include synoptic observations of geophysical phenomena over the whole surface of the Earth. At the Amsterdam meeting of the ICSU General Assembly in October

1952, its name was changed to the International Geophysical Year—1957-1958. It soon came to be referred to simply as the IGY.

Sydney Chapman best summarized the scope of the IGY, as finally conceived, in his general foreword to the first volume of the Annals of the IGY:

The main aim is to learn more about the fluid envelope of our planet—the atmosphere and oceans—over all the Earth and at all heights and depths. The atmosphere, especially at its upper levels, is much affected by disturbances on the Sun; hence, this also will be observed more closely and continuously than hitherto. Weather, the ionosphere, the Earth’s magnetism, the polar lights, cosmic rays, glaciers all over the world, the size, and form of the Earth, natural and man-made radioactivity in the air and the seas, earthquake waves in remote places, will be among the subjects studied. These researches demand widespread simultaneous observation.9

The Joint Commission on the Ionosphere recommended that a committee be es­tablished as a focus for the detailed planning. That committee was formally consti­tuted, also at the October 1952 ICSU meeting, as the Comite Speciale de l’Annee Geophysique Internationale (referred to universally as the CSAGI). The CSAGI cen­tral direction was entrusted to a bureau consisting of Sydney Chapman (President), Lloyd Berkner (Vice President), Marcel Nicolet (Secretary-General), Vladimir V Beloussov (Member), and Jean Coulomb (Member).

Four major meetings of the CSAGI, including representation from all participating nations, were held during the period 1953 through 1956 to coordinate overall planning by the many suborganizations and among the national programs. Those pivotal meet­ings tookplace at Brussels on 30 June-3 July 1953, Rome on 30 September-4 October 1954, Brussels on 8-14 September 1955, and Barcelona on 10-15 September 1956.10

During that early planning period, a series of Antarctic, Arctic, Regional, and Discipline Conferences were also held to serve as forums for integrating various

OPENING SPACE RESEARCH

components of the program. The Antarctic and Arctic conferences concentrated on the overall programs for those two regions, whereas the Regional conferences addressed the Western Hemisphere, Eastern Europe, Eurasia, Africa (south of the Sahara), and the Western Pacific.

The CSAGI established 14 Discipline Groups to plan many of the details.11

Responding to the invitation from the first CSAGI conference in July 1953 to countries of the world to join in the endeavor, the U. S. National Academy of Sciences, acting through its National Research Council, quickly established a U. S. National Committee for the IGY, with Joseph Kaplan as its chairman and Hugh Odishaw as its executive director. That committee served as the focal point throughout the duration of the program for all U. S. IGY planning and operational efforts.

Many other countries responded quickly to the invitation and set up their own mechanisms for coordinating their internal contributions. A key player, the Union of Soviet Socialist Republics (USSR), was slow in reporting its commitment to the IGY, but by the spring of 1955, it had also done so.