Category Dreams, Technology, and Scientific Discovery

ven while the Deal I satellite (Explorer I) was being assembled, work was moving forward steadily on the Deal II payload. While Deal I used only the Geiger-Muller (GM) counter, high-voltage power supply, and scaling circuits from my Vanguard design, the Deal II package contained my complete University of Iowa instrument, including its onboard data recorder.

Building the Deal II instruments

Only days before leaving Iowa City for Pasadena in November, I had finished con­structing the engineering test model but had not had time to draw the final detailed schematic diagrams. They existed only in scattered notes in my notebook and in my mind.

When I drove from Iowa City to Pasadena, the trunk of our car carried those notebooks, the engineering prototype package, and the parts that I had already begun accumulating for the flight instruments. Figure 10.1 shows the prototype Vanguard package as it appeared at that time.

The overall configuration of the Jupiter C version had been worked out through our exchanges in late October and early November. Although the outward appearance of the complete Deal II satellite was markedly different from that of the Vanguard satel­lite (a long cylinder rather than a sphere, as shown in Figure 10.2), the internal canister housing the University of Iowa cosmic ray instrument was quite similar. Some idea of that resemblance is seen by comparing the Vanguard instrument package in Fig­ure 10.1 with what became the Explorer II instrument cylinder shown in Fig­ure 10.4. The primary differences were (1) substitution of a JPL-designed high-power

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transmitter for the Naval Research Laboratory (NRL)-designed one, (2) changes to the NRL command receiver made necessary by the change to the two-transmitter (Minitrack plus Microlock) configuration, and (3) a change in electromechanical component locations necessitated by the higher spin rate.

Several tasks were especially pressing when I arrived at the Jet Propulsion Laboratory’s (JPL’s) gate. The first was to provide a catalog of needed parts. I completed a four-page list and turned it over to the JPL engineers on 4 December. They immediately placed a stack of rush procurement orders.

My second major task was to furnish workable schematic diagrams of my electron­ics design, which I drew by hand from the many sketches and notes in my laboratory notebooks. Most of those drawings were handed over to the JPL engineers by 16 December. However, I was still uneasy about a few of the tape recorder control circuit details. The engineers in JPL’s circuit development laboratory helped me with improv­ing those, and I eventually turned over the final schematic diagram on 9 January 1958.

Another urgent initial task was to arrange for the completion and installation of the onboard tape recorders. The tape recorder was unique—no comparable unit

CHAPTER 10 • DEAL II AND EXPLORERS II AND III

SUB CARRIER OSCILLATORS

AND

I KANSMITT ER ВАТТ ERIES

LOW POWER ANT GAP

AND TRANSMITTER

G M COUNTER

INSTRUMENTATION CYLINDER

COMMAND RECEIVER

PLAYBACK TRANSMITER

COSMIC RAY EXPERIMENT

ELECTRONICS

BATTERIES

>- TAPE RECORDER

HIGH POWER ANT GAP ■ROCKET CASING

FIGURE 10.2 The Deal II satellite. The six inch diameter instrumentation cylinder at the center of the figure contained the Iowa cosmic ray instrument.

was available from industry, and it would have taken too long for JPL to tool up to produce them. It was agreed that the instrument makers at Iowa, primarily Ed Freund, would complete the manufacture of four flight tape recorders. They would be shipped, however, with one task remaining undone. Ed had just completed the design of a new solenoid mounting bracket that converted the units from the Mark III to the Mark IV design, but had not yet machined enough for the flight units. We agreed that time would be saved if JPL machined the remaining mounts and installed the solenoids on them.

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On 26 November, I turned over the first completed recorder to Bob Garwood for him to begin making the modification. The second flight tape recorder arrived from Iowa on 5 December, and the others arrived at about one week intervals.

Also on 26 November, an engineer in Henry’s lab reported that he had been able to operate all of the Vanguard electronic circuitry in my prototype instrument package.

The JPL engineers had not been involved in designing the circuits in my cosmic ray package and had not had a hand in testing the components that I had selected. They established their own confidence in my work by building laboratory breadboard copies of many of the circuits and putting them through various tests. In only a few cases did they make minor changes.

We all shared a special concern about the performance of the onboard tape recorder in the more stressful environment of the Jupiter C launch vehicle. We were also anxious to verify the electronics packaging techniques that I had used. Although similar to those being used within the Vanguard project, some of the techniques were new to the JPL engineers.

Thus, we prepared a series of early vibration and spin tests using the Vanguard engineering design instrument package.[4] The JPL technicians mounted a new GM counter on my package to replace one that had been broken and installed a different turn-on plug on the top cover. We made the Mark IV modifications to the tape recorder and installed it in the package. Finally, we updated the wiring between the electronics decks.

They prepared a special mounting jig to attach the instrument package to the spin test facility. The initial results were encouraging. Everything, including playback initiated by the command transmitter and receiver, was normal up to a spin rate of 500 revolutions per minute (rpm). However, above that rate, recorder playback could not be reliably commanded. We were not sure whether the problem was in the tape recorder, in its control relays, or in interference to the radio frequency command signal caused by the noisy laboratory environment.

Milt Brockman suggested mounting a temporary test switch on top of the GM counter to bypass the command and control relays, in such a way that that switch could be actuated while the instrument was spinning. The engineers set up that ar­rangement overnight, and the next day, we made another spin test. The spin rate was increased to 1000 rpm, and operation was satisfactory. We then reconnected the playback relay, relocating it so that it was closer to the spin axis. During the next test, recorder playback was satisfactory up to 1100 rpm, but not at 1250 rpm. We concluded that the problem was with the relay, but we decided to proceed with it that way because the maximum spin rate during and after launch would be much lower at 750 rpm. The spin test series ended with a run with all of the sensitive

CHAPTER 10 • DEAL II AND EXPLORERS II AND III 267

components mounted in the positions envisioned for flight. That arrangement op­erated satisfactorily at 1190 rpm, but not at 1250 rpm. Again, we considered it acceptable.

A series of vibration tests of the cosmic ray package was uneventful. With the results of those vibration and spin tests in hand, I sketched the final internal physical arrangement for the Deal II cosmic ray instrument package on 9 December.2

Although the changes in the satellite program had substantially delayed my university course work, the objective of obtaining my M. S. degree was never far from my mind. Van Allen and I discussed that subject during several of our telephone discussions in early December, and he sent me a sample of a master’s thesis based on the development of another cosmic ray instrument. That helped me develop a feeling for the writing that I would have to do and provided additional motivation for very meticulous note taking.

A pivotal instrument review and planning meeting was called by payload manager Walt Victor for 11 December. Specific individuals were assigned responsibility for various portions of the work. The schedule called for the first flight unit to be shipped to Cape Canaveral on 10 February, with shipment of the second payload on 17 February. To make that schedule, the first State University of Iowa (SUI) cosmic ray package would have to be fully assembled and tested by 11 January, only one month hence, and the second unit would be required one week later.

That meeting served as the “starting gun” for the actual fabrication of the hardware. Following the meeting, Walt issued an “all hands” memo that began:

There is no pad in the Deal II schedule. All flight hardware must be completed on time and must operate satisfactorily in the environment [emphasis his]. It is suggested that all engineers consider the scheduled date as the absolute latest time the equipment can be made available, and that they make every effort to better the scheduled date whenever possible. I will be following the work progress very closely and expect to be notified immediately of any circumstances which would prevent making the schedule.3 I

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During much of January 1958, aside from my work on the GM counter calibrations, as recounted earlier, much of my effort went toward finishing and testing several of the Deal II circuits. In mid-January, a few design details on the tape recorder playback amplifier and relay control circuits were still being improved. One of those improvements was to add a protective circuit to unlatch the control relays in case the recorder should freeze, so that the batteries would not be drained if that should occur. My summary report to Van Allen on 20 January read:

Needless to say, all circuits which were not completely checked out when I left Iowa have now been. The recorder drive circuit [had not been], but has been found by now to operate from —25°C to +65° The playback amplifier required some rework, and now utilizes considerable negative feedback to stabilize its operating conditions. Its characteristics change very little from —25°C to +75°C. It delivers a saturated rectangular pulse to the modulator.4

That letter included a set of drawings for both the Deal I and II instrument packages, a five-page listing of all of the components being used in the flight payloads, and their selection criteria. I promised to send mechanical drawings in the near future.

I also reported:

My schedule is finalized now—will leave here the 26th, leave there [Cape Canaveral, not mentioned because of security] the 31st, arrive Iowa City the 31st at 2:05 PM, and leave Iowa City the 3rd at 2:15 PM. Had the thought that you might not be back in Iowa City by the 31st.

If not, will you send a wire? Also need the address at which I can contact you in Washington and your itinerary if possible.5

As mentioned earlier, I delayed my departure to Cape Canaveral for the Deal I launch until 28 January to make additional tests of the GM counter calibration setup and procedures. Even after those tests, I still had some reservations about the final calibrations. Beginning on 14 February, after I had returned from the Explorer I launch and my stop in Iowa City, I made a detailed assessment of the entire calibration setup, procedures, and results. After four days of work, I finally convinced myself that the calibrations were valid.6 I would have preferred to give the counters on the Deal II flight units a final run, but by that time, the first unit was already at the Cape. Any lingering concerns were not sufficient to warrant interfering with the remaining launch preparations.

By the end of Tuesday, 18 February, my work on Deal II appeared to be essentially complete, and it looked like I would be able to spend a few days at home with Rosalie and the two girls. My journal reported:

Payload I is built. It was recently pared down to remove weight, but is rebuilt. # II [the second payload for Deal II] is being built. There were three difficulties so far. (1) An internal short in receiver deck B2 caused a 150 ma. [milliampere] drain. Cleared OK. (2) Tuning fork deck D2 became intermittent. Replaced with D3. (3) This afternoon before leaving found out the playback head in recorder J2 was not delivering sufficient pulse amplitude. This will require disassembly & checking.7

CHAPTER 10 • DEAL II AND EXPLORERS II AND III 269

That marked the end of the payload development and assembly. During a long phone conversation with Van Allen on that day, we discussed many topics, including plans for preliminary analysis of the Explorer I data and for the upcoming Deal II satellite.

At the Cape, the JPL engineers were making several rather substantial last-minute modifications to the first Deal II flight payload mechanical structure. That included the substitution of a shorter shell, a lighter magnesium instrument container, and a lighter fretwork support for the low-power transmitter assembly. There was still considerable concern about achieving a sufficiently high orbit with a payload that was somewhat heavier than Explorer I, and every step imaginable was taken to reduce its weight. The other two Deal II flight payloads were modified in similar fashion at JPL before they were shipped to the Cape.

My brief respite was short-lived. On the 19th, two developments put me back into the crisis mode. The first was a failure during the environmental testing of the spare flight payload (the third Deal II payload). The recording amplifier quit operating, and the instrument would not respond to interrogations during the vacuum chamber test. After I analyzed the problem the next morning, the JPL engineers set about to repair it.

I turned my attention to the second crisis, the lack of readiness of the ground stations that would be needed to interrogate the satellite’s tape recorder. That problem is discussed in the next chapter.

Ernest C. Ray, or Ernie, as all his associates knew him, was born on 23 February 1930 in St. Joseph, Missouri, and he grew up in that city as a bright youth in a stimulating household. In high school, he was in the marching band as a clarinetist, in theater, and unusually active in the Boy Scouts, where he attained the rank of Eagle Scout.

Following high school, Ernie began his college work at Saint Joseph Junior College. Since he had settled upon physics as his primary academic interest, and as Saint Joseph did not offer a physics curriculum, he moved to the University of Iowa after his second year at St. Joseph. He received his B. A. degree in the fall of 1949. He continued there for all of his graduate work, receiving his M. S. and Ph. D. degrees in 1953 and 1956, respectively.

During his graduate study years, Ernie served several stints at Princeton University, New Jersey, working on the Matterhorn nuclear fusion project. Throughout his years at Iowa, he made major contributions to the research program through his study of, and keen insight into, physics and, particularly, the motions of charged particles in the near-Earth region.

Following receipt of his Ph. D. degree, Van Allen offered him a series of faculty positions, first as an instructor, then as an assistant professor. He remained there until June 1961, when

CHAPTER 12 • DISCOVERY OF THE TRAPPED RADIATION

he took a short appointment at the RAND Corporation at Santa Monica, California. In early 1962, he joined the research staff at NASA’s Goddard Space Flight Center. Moving for a year and a half to Cornell University in Ithaca, New York, he returned to Goddard in early 1965.

By that time, his friends noted a marked personality change. His creative contributions to Goddard’s research waned, he stopped publishing, and it became increasingly difficult to converse with him. His descent into the depths of acute schizophrenia continued to the point that he was committed to a mental health institution in 1970. He remained there, in halfway houses, and in other transitional facilities for the rest of his life. In his later years, he became a valued volunteer at the Baltimore Fellowship of Lights, an organization that provides assistance for runaway youths and their families. In that environment, he managed to maintain his dignity and live a useful life until he died, in December 1989, of kidney cancer and chronic lung disease.

With the failure of the Explorer V launch and the NOTSNIK attempts, the Argus Project was left with only Explorer IV to obtain the crucial orbital data coverage. Fortunately, the satellite operated perfectly for nearly two months, from 26 July until 21 September, well after the Argus detonations.

It was important to obtain data from the full range of latitudes covered by the satellite for both an expanded study of the naturally occurring radiation, and for detecting and measuring the Argus Effects. The full suite of Minitrack stations es­tablished earlier as part of the Vanguard program was used. Additional stations were set up to extend the orbital coverage and, most important, to provide coverage at the higher latitudes. The full suite of stations used for Explorer IV data reception was impressive:

The initial month’s data from Explorer IV established the natural conditions in the Earth’s radiation trapping region and showed rather small responses to the lower- altitude Teak and Orange bursts on 1 and 12 August. When the first Argus nuclear device was detonated on 27 August, the satellite easily and promptly detected the

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resulting particle shell and did likewise for the two bursts that followed on 30 August and 6 September.

On 24 August 1958, the day after the Explorer V attempt, I was feeling completely worn out and swamped by the work ahead. Work was progressing on PL-16 (the precursor to Explorer 7); planning for a number of lunar probes was heating up; and I was heavily involved in the Explorer I, III, and IV data reduction. Additional missions were being discussed. On top of that, Van Allen was on vacation on Long Island, so I had only infrequent telephone contact with him to resolve issues. A new academic semester was about to start. I had not been taking courses for most of the year and was very concerned about completing the work for my master’s and Ph. D. degrees. On that day, I expressed some of those concerns by writing in my journal:

The future is confusing, and a big question mark. At least four projects can be seen in the near future, with no sign of a letup. This in view of the fact that I planned to return to school this fall. I can hardly bear to think of not obtaining my Ph. D., yet, how can I escape from this other work. My family is another consideration. I have been away from them so much the past year, … I cannot continue to spend one hour per day or less with my family and expect to have a livable home relationship and happy, well-adjusted children.17

That difficulty was resolved to a satisfactory degree at the end of the month. By then, Van Allen had returned to the campus and he, Carl McIlwain, and I were able to sit down for an extended discussion of the laboratory’s space-related work. At that meeting, I stated that I would be unable to continue the combination of the heavy instrument development and management load that I had been carrying, plus the work on the data and an academic load. We agreed to limit our total laboratory efforts to three major project series and to split them up among us. I would continue with the Explorer activities, Carl would take the Space Technology Laboratories’ lunar shots (Atlas-Able and Pioneers 1 and 2), and Van Allen would take the JPL lunar shots (Pioneers 3 and 4).18

I promptly signed up for courses in Classical Theoretical Physics and Nuclear Physics.

The decade of the 1950s was marked by an unusually good spirit of cooperation among the scientists who participated in the Great Space Endeavor. It was furthered by the spirit of common purpose and cooperation engendered by the IGY.

I was greatly impressed by the proceedings at the pivotal meeting of the Upper Atmosphere Rocket Research Panel at Ann Arbor in early 1956. The summer before, the president had announced the goal of orbiting an artificial Earth satellite as part of the U. S. participation in the IGY. That presented a wonderful opportunity for many scientists to realize their long-standing dream: to observe our earthly home from well above the atmosphere.

One would have to admit that the possibility of participating in that grand adventure might have engendered a fierce competition with many negative aspects. That did not happen. Never once did I observe an instance of a scientist trying to gain a

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foothold by attacking a potential competitor. The competition was marked by efforts by prospective participants to convince their research colleagues of the validity and superiority of their own ideas. When decisions were made, one way or the other, there was a willingness to proceed on that basis, with a minimum of backbiting and other destructive behavior. Never, throughout the entire period leading up to and including the IGY, did I observe a substantial instance of untoward selfishness, destructive competitiveness, or power brokering among the many established and emerging scientists with whom I was in contact.

The “let’s get on with the job” spirit enabled many amazing accomplishments. Excep­tionally short development times were possible that astound those looking back from the present vantage point. Explorer IV was planned, approved, and launched within a period of 77 days.

The spirit of the 1950s made it possible for individual graduate students to conceive of experiments, build the instruments, launch them into space, collect and analyze the data, and publish results during the few years of their university studies. Although that form of end-to-end experience can still be gained today with some balloon and rocket studies, it is rare with most of the current, more ambitious space experiments.

It takes years and even decades to develop some of today’s instruments. A large share of the difference must, of course, be attributed to the vastly different scale and complexity of the experiments. It is an inescapable result of the maturing and broadening of the field. As a result, today’s far grander instruments are bringing us a cornucopia of spectacularly beautiful and important revelations about the nature of the universe that could not otherwise be gained.

Despite today’s great capabilities, there remains a persistent longing by many of us “old-timers” for the relative flexibility and freedom that we enjoyed in that bygone era. The pressures during the 1950s were great, and we worked long hours, but it was a period of tremendous excitement and achievement.

For any researcher, and especially for a student, an environment in which the full spirit of the Sigma Xi motto “Companions in Zealous Research” prevails is a true blessing. Many of us benefited tremendously from that environment during those early years of the Space Age.

An ambitious rockoon expedition was mounted in 1955 as a follow-up to the earlier ones. It had three goals. The first was to further clarify the latitude distribution and nature of the auroral soft radiation observed during 1953 and 1954. The second was to continue the original cosmic ray latitude survey by testing a new lighter-weight and even less expensive rockoon. And the third objective was to test a two-stage rockoon configuration in an attempt to reach even higher altitudes.

Frank McDonald was the principal investigator for the first of those objectives and served as the expedition’s team leader. He used the well-tested Deacon rockoon configuration, but with a more advanced instrument that combined most of the features

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of the separate instrument packages flown in 1954. It included the twin-GM counters with different amounts of shielding, plus a scintillation detector generally similar to that used in 1954, but with two important changes. The 1954 detector had been coupled with an additional GM counter to form a telescope to determine the directional characteristics of the auroral soft radiation. Since that radiation had proved to be too soft to activate the telescope, that GM counter was dropped for 1955. Second, a nose cone of somewhat thinner material was used, and the scintillator crystal was located beneath a 0.002 inch thick titanium foil window at the tip of the nose cone to further reduce the amount of shielding in front of that detector. The 1955 instrument package is shown in Figure 2.8 beside its nose cone shell.

I participated in that operation as an undergraduate senior. The preparatory work became all-consuming during the summer, beginning immediately after I finished my spring semester courses. I did much of the design, construction, and testing of Frank’s new instruments. I also developed and set up the associated ground receiving, processing, and recording station used during the expedition to recover the flight data and, upon our return, to process the data for analysis.

FIGURE 2.8 The Deacon instrument pay­load for the summer 1955 rockoon expedition. The scintillation counter is at the top, followed by the two GM counters. Next are two decks con­taining scaling circuits, a deck containing mis­cellaneous electronic circuits, the batteries, and finally, the transmitter. The flat on top of the nose cone contains the thin titanium window for the scintillation detector. The complete pay­load weight was about 40 pounds. (Courtesy of the Department of Physics and Astronomy Van Allen Collection, The University of Iowa, Iowa City, Iowa.)

It was a special thrill for me to accompany the field expedition in the early fall. The work on that project provided excellent advanced training in the techniques of high-reliability instrument building and scientific field operations that was invaluable when I began designing satellite instruments the following spring.

The second goal of the 1955 expedition was to develop and test a smaller rocket and payload to further exploit the advantages of the rockoon technique. Van Allen had thought that a three inch diameter Loki Phase I rocket might be used in place of the six inch Deacon. He had discovered that a considerable number of those surplus Loki rockets were stocked within the Army Ordnance Department, and some of them were made available to SUI without cost through arrangements by his friend and col­league, William H. Pickering, director of the Jet Propulsion Laboratory in Pasadena, California. Those lighter payloads could be lofted by smaller balloons—39 feet in diameter with a volume of 26,000 cubic feet—which were available at a cost of only about $200. The lighter weight and smaller size of the Loki configuration had another big advantage in that it was easier to handle and launch than the larger Deacons.

Van Allen’s vision was that, if a meaningful instrument could be made sufficiently small and light in weight, a substantial fleet of them might be flown as a part of the SUI scientific contribution to the upcoming International Geophysical Year. When he met with his new graduate students in August 1954, this was among the new ideas

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that he put on the table for consideration as research projects. Carl McIlwain was one of those new graduate students.

The first entry in my notebooks dealing with actual hardware design is dated 27 March 1956.8 On that date, I began breadboarding several transistor circuits that I had found in Electronics magazine.9 Although those circuits served as a starting point, they required far more electrical power than we could afford. I used a binary scaler (variously referred to as a binary counting circuit, flip-flop, or bistable multivibrator) as my learning tool.10 As for the transistors themselves, at first I used several early germanium types that had been identified in the Electronics magazine articles. They gave mixed results, with their high leakage currents making the necessary extreme power reduction problematical. A sample of a new type of surface barrier germanium transistor (Philco type SB-100) arrived at the laboratory on 4 May 1956. It was the first readily available production transistor that had the low leakage current, stability, and uniformity that I needed. I immediately began testing those transistors in my circuits and continued to use them until more desirable silicon transistors became available later that fall.

The Vanguard engineers at NRL were busily developing various electronic circuits and testing components for the satellite program, and they and the experimenters freely exchanged information on our respective efforts.

Instrument development went into high gear in early May 1956. From that date forward, my notebooks are full of descriptions of preliminary, intermediate, and final designs; of meetings attended; and of records of telephone calls to coordinate with the NRL engineers, program managers, IGY officials, and other experimenters. They also record literally hundreds of calls to collect information about suitable components and equipment, including everything from transistors to resistors, capacitors, time standards, recording and playback heads, recording tape, gears, bearings, switches, batteries, circuit board materials, encapsulating materials, and environmental test chambers.11 Those contacts continued throughout the entire duration of the project.

My notebook entry on 9 May contains a rough sketch of the complete block diagram for our cosmic ray instrument. By 10 days later, it had taken the form shown in Figure 5.1.12 By the time Explorer III was launched in 1958, only three major changes were made to that design: a change from a drum to tape as the data storage medium, the addition of a continuously transmitting channel, and a change in the encoding scheme.

CHAPTER 5 • THE VANGUARD COSMIC RAY INSTRUMENT

FIGURE 5.1 Block diagram from the author’s laboratory notebook of the University of Iowa satellite cosmic ray instrument as it existed in May 1956 during its development as a part of the Vanguard program.

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May 1956 A meeting of the Working Group on Internal Instrumentation at the Naval Research Laboratory from 31 May to 1 June presented our first opportunity to report on our progress. Homer Newell began that meeting by stating, “We [collec­tively] are entering the brass tacks phase.” He announced that the most likely date for the first launch would be the fall of 1957 and listed the specific national objectives that had been established for the Vanguard program. They were (1) to put an object in orbit around the Earth, (2) to prove that it was in orbit, and (3) to conduct at least one scientific experiment using its internal instrumentation.

In terms of the physical arrangement of the planned Vanguard satellite, He stated that “[the] party line so far is 21.5 lb., 20-inch sphere. Line of retreat—no payload— third stage bottle only—18" dia. x 50" lg.” Following his general introduction, the by-then-active experimenters outlined their individual plans and the status of their developmental efforts.

Our status report included the block diagram shown in Figure 5.1, a full expla­nation of its operation, and a listing of expected characteristics. They included an expected instrument weight of 2.66 pounds (exclusive of the transmitting and receiv­ing equipment and their batteries), sizes and volumes of modules, and a total power requirement of 80.9 milliwatts.13

July 1956 Another pivotal technical working session was held at NRL on 30 and 31 July 1956.14 As far as our Iowa instrument was concerned, the most significant progress included a first attempt to detail the overall physical arrangement, good progress in designing the data recorder and electronic circuits, and investigation of sources for components and fabrication materials.15

Although the initial evaluation of GM counters embraced a wide variety of types, Van Allen’s familiarity with the devices in general, and, in particular, with the halogen- quenched counters that Herbert Friedman had developed at NRL, soon narrowed our focus. Halogen-quenched counters were being produced on a routine basis by the Anton Laboratory in Brooklyn, New York, and Van’s longtime association with the laboratory’s founder, Nicholas Anton, paved the way for a wonderfully effective association. Anton and his chief engineer, Herbert Kalisman, were extraordinarily helpful throughout those early years, when they produced numerous special versions for our evaluation, often within only a few days.

The choice of halogen-quenched counters for the Iowa instruments turned out to be fortuitous. They operated in orbit without degradation for the satellites’ entire lifetimes, in spite of the unexpected extremely high counting rates resulting from repeated incursions into the Earth’s trapped radiation. In retrospect, had we used the more conventional alcohol-quenched counters, they would almost certainly have failed before the end of the satellites’ operating lifetimes because of the high radiation intensities that they encountered.

CHAPTER 5 • THE VANGUARD COSMIC RAY INSTRUMENT 133

Well before the July meeting, I was becoming convinced that a major change would have to be made in the recorder design. The storage medium in the initial Mark I design was a cylindrical drum surfaced with ferric oxide. The recording and playback heads were to be supported above that surface by a very small gap. As the drum rotated, it would move axially, producing a continuous 18 inch long data track as a spiral around the surface of the drum.

I abandoned that drum approach in late June after realizing how rapidly the pulse packing density decreased with increasing head-to-recording-surface spacing. That spacing would have to be as small as 0.5 mil (0.0005 inch), and problems of drum concentricity would be large.16

Using tape instead of the drum permitted the recording medium to ride in direct contact with the heads. The tape version was identified as the Mark II recorder, and by the time of the July meeting, our instrument shop had produced a very rough first unit that I was able to show to the attendees.

The Vanguard technical discussions at the July 1956 meeting included details of the launcher, satellite structure, temperature control, some of the circuit development efforts at NRL, telemetering and radio commanding, and environmental testing. We saw a mockup of the by-then-envisioned satellite structure. Its exterior shell was a 20 inch diameter sphere consisting of two aluminum hemispheres joined at their equator. It was stated that the shell would have a 40 micron coating of silicon monoxide for temperature control.

Internally, the shell contained a small cylindrical chamber at its bottom to house a spring mechanism for separating the satellite from the final rocket stage. A larger cylinder for the scientific instrument was mounted on top of the separation mechanism, supported on its sides by a cantilever structure fabricated from welded aluminum tubing. The model was shown with a 3.5 inch diameter instrument cylinder, and the meeting discussions focused on that size. It was stated, however, that the instrument cylinder could be as much as 6.5 inches in diameter, and it was on that basis that we proceeded with our 6 inch configuration.

One-quarter wavelength antenna rods were mounted on the exterior of the shell’s equator. They were to be folded for launch and snapped into place on tapered me­chanical sockets following satellite separation.

October 1956 The Working Group on Internal Instrumentation held its third meet­ing at NRL on 9 October 1956. By that time, NRL was well along in designing the two different models of the satellite. The first was to contain the 3.5 inch diameter version of the scientific instrument package, and the other was for the 6 inch version.

Throughout the program, Van Allen and I conversed frequently, in his office, the laboratory, the hallways, or over lunch, to review progress and to exchange ideas about the instrument development. It was at just such a discussion on 22 September that we

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agreed to increase from a single to two channels of telemetry, one for continuously transmitting the raw counter rate and the other for transmitting the tape recorder data readout upon ground command.

At that time we addressed the question of possible effects of cosmic radiation on the transistors. Van Allen had become concerned that cosmic ray interactions within the body of the transistor chips might either trigger false results or, in extreme cases, damage the devices. After some back-of-the-envelope calculations, he concluded that reasonably expected cosmic ray rates should introduce less than one interaction in a one cubic millimeter pellet during an entire orbit—an acceptable error rate, even if all of those interactions should result in false counts. He also concluded that the chance of damage to the chips would be remote.

On a different subject, Van Allen mentioned that Wayne Graves, an engineer at the Collins Radio Company in Cedar Rapids, was interested in working on the satellite. He soon made the necessary arrangements with his friend Arthur Collins, and Wayne worked closely with me on the instrument development and testing from that October until June 1957. A very capable engineer, he helped tremendously in the design and testing efforts.

By the time of the October meeting, our work on the satellite instrument had progressed substantially. Major work on electronic circuitry had been completed, and many electronic and mechanical components suitable for flight had been chosen. Silicon transistors from the Texas Instruments Company had entered the picture. Their new 2Nxxx series was coming into early production. I had received early samples and found that their temperature and electrical properties were far superior to the germanium units that we had been using.

Van Allen and I had initially expected that we would contract with a commercial firm to complete the design and fabricate the tape recorders. My telephone discus­sions and visits to several prospective manufacturers proved disappointing, however, and we decided to build them in-house. Our instrument makers had completed the first Mark II recorder, shown in Figure 5.2, and I was subjecting it to extensive testing.

By that time, I had evaluated and ordered the first of a number of new environmental testing facilities. It was a temperature chamber, capable of testing our components and modules at both high and low temperature extremes.

The October 1956 meeting focused on detailed satellite design. A new satellite weight allocation listed 2.00 pounds for the shell, 1.10 pounds for the internal support­ing structure, and 2.50 pounds for our internal experiment packages, including their thermal-mechanical control switches, but not including the telemetering components. The spring device to separate the satellite from the final rocket stage was projected to weigh 1.00 pound. The Minitrack telemetering system, consisting of the antennas, transmitter, and batteries, was estimated at 6.07 pounds. One pound was set aside

for wiring and miscellaneous items. That made a total projected satellite weight of 13.67 pounds.

December 1956 As 1956 was ending, a meeting at NRL of the Vanguard Science Program Committee reviewed the status of the satellite development and worked out additional technical details. By then, we had progressed from general system de­sign to very specific engineering details—the meeting discussions concerned satellite structure, internal temperature control, instruments, the environmental testing pro­gram, and orbit details. The results of internal NRL design work on circuits, batteries, telemetering, and ground receiving station recording received considerable attention.

With respect to our Iowa instrument, by December, the most substantial accom­plishments included extensive thermal testing with our new temperature chamber, finalization of the data-encoding scheme, and more changes to the data recorder.17

My greatest problem with the recorder had been in controlling the speed of the tape during playback. It was necessary to control the speed of the tape to produce

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a reasonably constant data rate for transmission. To initiate playback, a ratchet was released, permitting a spring to rewind the tape onto the supply reel. A normal spiral – wound spring provides a torque that varies considerably as it winds and unwinds. Attempts were made to find a spring formed in an S shape that would provide a more nearly constant tension (a so-called Negator spring), but I was unable to locate a suitable source.

The Mark II version had employed a mechanical governor having centrifugally actuated brake shoes in frictional contact with a stationary drum. That approach could not be made to work smoothly in such a small configuration. For the Mark III version, I used an eddy-current speed controller, where a retarding torque was produced by a silver disk rotating at high speed in a strong magnetic field. Since the retarding torque in such an arrangement varies as the square of the rotational speed, it provided a rough but acceptable speed control. The result was a 6.5 second playback time for dumping the entire tape content, with a speed variation of less than a factor of two during the playback. That speed variation, although certainly not desirable, was compensated for in the ground data processing.

I had been using ordinary consumer-grade Mylar-based recording tape but was concerned about its durability in the space environment. My greatest fear was that the recorder might get warm enough for the Mylar to stretch. I finally located a metal recording tape that had the desired ruggedness and dimensional stability. The UNIVAC I computer that had been introduced in 1951 by the Univac Division of Remington Rand in Philadelphia employed a 0.5 inch wide by 0.001 inch thick phosphor bronze recording tape with an electroplated nickel-cobalt recording surface. Rand donated a twenty-five foot length of that tape. I arranged with the tape’s original manufacturer, the Somers Brass Company in Waterbury, Connecticut, to slit this length of tape to the desired narrow 5/32 inch width. A 55 inch long piece of that tape was incorporated in each Mark III and IV recorder.

The tape-advancing ratchet was also redesigned. The Mark II mechanism had been unbalanced. I was concerned about the effect of vibration, acceleration, and spin on that device and designed a more completely balanced version for the Mark III recorder.

I had had great difficulty in finding very small but sufficiently high performance recording and playback heads. Throughout the summer of 1956, I obtained specifi­cations and samples from every supplier I could locate. In early October, I obtained new samples from the Dynamu Division of Maico Corporation, a maker of consumer- grade reel-to-reel tape recorders. Finally, I had heads that were small enough to fit in the recorder but which still had good enough high-frequency performance to produce the desired data packing density on the tape. The recording head had a gap width of only 0.00015 inch, quite remarkable for that time.

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Other changes in the Mark III version were relatively minor, but they illustrate the extreme care taken to assure high reliability. The three metal idler rollers were replaced by ones made of Teflon, which has a slippery surface. Thus, if a bearing were to freeze, the tape could still slip across the idlers and permit the recorder to operate. Finally, a pair of cam-operated mechanical limit stops was added to augment the previously included electrical limit switches. Then, if there should be an electronic failure, the mechanical stops would stall the tape to assure that it could not be pulled off the tape reels.

It was announced at the December meeting that NRL would deliver a first aluminum prototype satellite shell on 30 January 1957 for our use in test fitting the cosmic ray instrument package and for initial system tests. The first two magnesium models were due on 1 May. One of those was earmarked for our system testing at the State University of Iowa (SUI), while the second (the true prototype model) was to be delivered back to NRL with our instrument package installed for the tests that they were to conduct. Three flight models of the satellite shells and instrument supporting structures were due to us at Iowa City on 15 June.

One important action taken at the December meeting was the naming of spe­cific NRL individuals to work with each of us. The team for our Iowa instrument consisted of Leopold Winkler as chairman, Robert (Bob) C. Baumann for mechan­ical structures, Milton Schach for internal temperature control, Roger Easton for the radio frequency components, and Whitney Mathews for the telemetry system. The group’s initial charge was to review our complete system, prepare a break­down of the relative NRL and SUI responsibilities, and review the SUI instrument budget.

Our transmitters and receivers were also being built by NRL. A first transmitter was promised for 30 January. Their first receiver was due on 15 February. The second transmitter, able to switch between two power levels to accommodate our two-channel instrument design, was due on 1 March. Four flight units of both the transmitters and receivers were scheduled for delivery to us on 1 May.

We scheduled a first vibration test of a prototype data recorder for 1 February. One completely assembled cosmic ray instrument package was due in Washington on 1 May 1957 for environmental testing at the design levels, and three flight models were promised for 15 June.

Henry Richter began his JPL work as a research engineer in Bill Sampson’s New Circuit Elements Group in the Electronics Research Section. This began soon after receiving his Ph. D. degree in chemistry, physics, and electrical engineering in 1955 at CalTech. It took several months for his security clearance to be issued, so Henry was excluded from any involvement in the strange classified work being conducted on the roof of his building. Those were early tests of the embryonic Microlock system by Sampson, Eberhardt Rechtin, and their staffs. Based on those tests, Microlock was written into a feasibility study and, from then on, was included in the army’s satellite planning.

One of Henry’s early assignments, even before receipt of his security clearance, was to “start thinking about batteries that might survive a missile launching, and then operate under conditions of high vacuum and widely varying temperature, and which could function over extended periods while weightless.” It didn’t require a genius to guess what was afoot. As soon as Henry did receive his clearance, he was given part of the satellite feasibility study to work on, and he began to understand more fully the full character and significance of the work. He went on to become a major leader and participant in the development and application of the Microlock system and in the design and building of the early Explorer satellites.36

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Work on development of the Microlock system progressed steadily during the summer and fall of 1955. That winter, Henry Richter, with one of his engineers, William (Bill) C. Pilkington, scoured the country looking for transistors that could operate effectively at the 108 MHz frequency envisioned for the satellites. By March 1956, the system development had progressed to the point where field testing could proceed.

The Redstone RTV booster rocket contained several measuring and telemetering systems to provide information about the performance of its control system and motor. None of those, however, provided information about the flight performance of the high-speed stages, most notably, temperatures in the nose cone during its reentry through the atmosphere. Two Microlock transmitters operating at different power levels were placed in the test vehicle for that purpose. They flew on the first all-up RTV flight that September.

Four Microlock ground stations were set up to support that first launch. Although they were justified because of their need for the nose cone-testing program, the selection of ground sites was substantially influenced by the anticipation that the system could later be used for satellites.

A station at the launch site was, of course, essential. It was needed to help with the checkout of the flight equipment before launch and during the rocket ascent. A second station was set up at Huntsville. That location was within the circle of visibility for much of the trajectories of the Jupiter C nose cone test flights. The existing Sergeant­testing station at the White Sands Proving Ground in New Mexico was refitted for the Jupiter C nose cone test flights, as over half of their flight trajectories were visible from that location. Being in an area that had less radio interference and that was at a greater distance from the flight trajectory than Huntsville, it yielded a better measure of system performance applicable to later satellite flights.

A fourth Microlock station served primarily as a site for Microlock developmental field experiments. JPL conducted their first system tests by helicopter overflights in the Pasadena area in early 1956. It soon became necessary to make more sensitive and discriminating tests, for which the entire Los Angeles area had far too much radio interference. After extensive surveys, they settled on a location somewhat north of the midpoint of a line between San Diego and El Centro, California. Near the Anza – Borrego Desert State Park, it is located in a valley known as Earthquake Valley, with mountains to the west, north, and east. That nearly ideal location very effectively cut off radio interference from all heavily settled regions.

The Earthquake Valley test station was established in early 1956, and helicopter overflights were conducted there during March. The engineers at those tests, including Cliff Finnie, Bill Pilkington, Phillip (Phil) Potter, Henry Richter, and Robertson (Bob) C. Stevens, demonstrated that the system would be capable of conveying data from a satellite or space probe from over 20,000 miles away.

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For the Jupiter C ABMA-JPL collaborative effort, including both the RTV testing and their behind-the-scenes satellite work, the many groups at Huntsville and Pasadena worked together very harmoniously. The combined efforts required a highly interac­tive and iterative process, with every change affecting many other parts of the program. Frequent meetings helped to keep the work closely coordinated. Both laboratories de­veloped great respect for their counterparts. There were, of course, disagreements that required high-level decisions. Most of those were worked out directly between the two project managers: von Braun at Huntsville and Froehlich at Pasadena. Their decisions were accepted and implemented with goodwill.

Another undercover satellite effort The JPL participation in the ABMA-JPL col­laboration, including the integration of their Microlock system in the ABMA-designed satellite, was not the whole story. Apparently unknown to their ABMA counterparts, JPL undertook, at the same time, the design of their own version of a satellite for launch on the Jupiter C.

To step back a moment in time, the JPL had actually entered the competition for scientific payload space very early in the IGY satellite program, when they began working out the details of their own cosmic ray experiment proposal. Pickering first wrote about it to Van Allen (the latter as chairman of the Working Group on Internal Instrumentation) on 5 July 1956. His plan was formally submitted to the IGY over Eberhardt Rechtin’s signature on 26 July 1956. The proposal included three parts:

(1) an ion chamber for cosmic ray research by Victor Neher on the CalTech campus,

(2) photoelectric photometry of the sky by William Baum, an astronomer at the Palomar Observatory, and (3) an engineering-related data transmission and reception experiment to study their Microlock system performance by the JPL engineers.

That proposal was given for action to Van Allen’s Working Group on Internal Instrumentation that the U. S. National Committee’s Technical Panel on the Earth Satellite Program had established to deal with Vanguard experiment proposals. The Working Group on Internal Instrumentation identified it as Earth Satellite Proposal 27 (ESP 27) and assigned it a Priority B rating at their 11 October 1956 meeting. Not being included on the highest priority list, the IGY program did not provide funding and approval for further development.

The planning for it remained active at JPL, however, until at least 9 May 1957, when Richter made a trip to NRL to discuss the integration of ESP 27 into the Vanguard satellite.

Early thinking at JPL was that their instruments might be included in a satellite of their own making. That claim is substantiated by the appearance, in a CalTech-issued magazine in the summer of 1957, of an article by Pickering describing “how the lab could ‘completely instrument one of the [Jupiter C] vehicles’ with a cosmic ray

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experiment developed by a CalTech professor and another instrument from a Palomar Observatory astronomer.”37

By April 1957, JPL had shifted from that approach to focusing on our University of Iowa cosmic ray instrument instead of their own instruments. It had the advantage of being a Priority A instrument in the Vanguard instrument lineup and therefore of having the full endorsement and support of the U. S. IGY program. The fact that we had designed it to fit either the Vanguard or the Jupiter C configuration also figured in their thinking. Those factors led to the visit by Eberhardt Rechtin to Iowa City on 23 May 1957, as discussed in more detail in the next section.

By the time of the Sputnik 1 launch in October 1957, the JPL satellite development had progressed to the point that considerable prototype hardware had been built. The low-power transmitter assembly that I saw soon after my arrival at JPL in November was one physical manifestation of that situation. Models of the complete satellite later found their way into various museums, including the Griffith Observatory in Griffith Park, Los Angeles.

At the University of Iowa We at the University of Iowa Physics Department became involved in the various Jupiter C satellite-launching planning efforts through a long chain of events. Ernst Stuhlinger had been generally aware of Van Allen’s research even before the beginning of WWII. The two first met during the immediate post- WWII period, after Stuhlinger had arrived in the United States. Van Allen, by then a young upper atmosphere scientist at the Johns Hopkins Applied Physics Laboratory, was flying cosmic ray instruments on some of the V-2 rockets that had been brought to the United States. Stuhlinger was coordinating the interface between the rocket engineers and the researchers.

As mentioned earlier, Stuhlinger suggested to von Braun in 1952 that Van Allen would be a good choice of an experimenter to place a scientific instrument on the satellite that they envisioned. Stuhlinger and Van Allen first discussed that subject when Van Allen was at Princeton University on leave from the University of Iowa in 19 5 3—19 5 4.38 During a visit there with Van Allen in mid-1954, Stuhlinger described the ABMA thinking about a satellite, emphasizing the opportunity to fly Geiger counters. Stuhlinger later related:

When I had finished my sales talk and waited for Dr. Van Allen’s show of interest, he only said, “Thanks for telling me all this. Keep me posted on your progress, will you?”—I was disappointed by this apparent lack of interest, but then I remembered from our meetings at White Sands that Dr. Van Allen was a very cautious scientist, far too careful to jump to any conclusions. So I understood his restrained response, and I kept him posted on our progress. Von Braun informed Dr. Pickering, at that time Director of the Jet Propulsion Laboratory, of our contact with Dr. Van Allen, and received the latter’s full endorsement of our step.39

That discussion had the effect of heightening Van Allen’s excitement about the prospects for extending his cosmic ray research farther into space.40 He immediately

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prepared an outline for a satellite-borne cosmic ray experiment and sent it to Stuhlinger.41

A year later, soon after President Eisenhower’s announcement of the U. S. intent to launch a satellite, Van Allen updated that proposal and submitted it to the U. S. planners of the IGY endeavor.

At that point, I had just returned from the summer 1955 rockoon expedition to northern Greenland and was completing the work for my bachelor’s degree. I would soon need a graduate research project. Van Allen and I began discussing specific details of the satellite instrument, with the general understanding that its development and flight might serve that purpose.

The discussions between Van Allen and Stuhlinger figured importantly in arriving at the physical configuration of the Iowa cosmic ray instrument package, even while it was being designed for the Vanguard launch vehicle. The NRL initially specified that their 20-plus inch diameter spherical satellite would contain an internal instrument cylinder 3.5 inches in diameter.

Van Allen stated his preference that the overall form of the satellite should be a right circular cylinder approximately 6 inches in diameter and 18 inches in length. He believed that that configuration would provide the most efficient packaging for the scientific instruments. Since that had been the diameter of the instrument payloads that we had built for the Deacon-based rockoons, our laboratory had extensive experience with that particular envelope.

Van Allen formally expressed that preference in a letter to the Technical Panel on the Earth Satellite Program in late January 1956.42 Specifically, he proposed that half of the IGY payloads be built in the original 20-plus inch diameter spherical form, identified as Mark I, and that the other half be of a new Mark II configuration, in the cylindrical form that he preferred.

The Vanguard program staff responded with a compromise—by changing their specifications to permit either a 3.5 or 6 inch instrument package to be housed within the outer 20.5 inch diameter spherical shell. Although not going as far as Van Allen wished, that change did allow us to use the six inch form factor in developing our cosmic ray instrument.

Beyond any doubt, Van Allen’s preference for the six inch package was strongly in­fluenced by his knowledge that the Redstone-based vehicle could accept that package with little change, if problems should develop with the Vanguard launch vehicle.43

Stuhlinger told Van Allen about the first fully successful test flight of the RTV during a telephone conversation on 16 November 1956, about two months after its occurrence. During that discussion, he expressed his continuing grave doubts about the realism of the Vanguard launch schedule and encouraged Van Allen to suggest a specific

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cosmic ray instrument that could be used in the Jupiter C payload. Van Allen did that informally during the discussion and followed it on 13 February 1957 with a letter proposing a specific instrument package. Part of his letter read:

Dear Ernest [sic]:

1. We are delighted to know that there is a possibility of flying some scientific apparatus on one or more of your orbiters. . . .

It is my understanding that a total payload of 15 pounds is now regarded as feasible. In consideration of what types of scientific apparatus may be appropriate I have taken two pounds as a reasonable weight. And, of course, I have depended rather heavily on the considerations in which our I. G. Y. Working Group on Internal Instrumentation has been engaged for over a year.

I have assumed no data storage of the type which requires command readout and have also assumed that the I. G. Y. 108 mc/sec telemetering stations will be available, or that a substantial Microlock array will be available.44

The letter continued by listing all of the experiments being considered for the Vanguard program. Those, in addition to Van Allen’s cosmic ray experiment, were experiments dealing with solar ultraviolet and X-ray fluctuations, meteoric erosion, air density, the Earth’s radiation balance, cloud coverage, and ionospheric measurements. The letter closed:

4. Needless to say, our group here at the State University of Iowa is very eager to participate in your program. We now have all the appropriate elements of a suitable cosmic ray apparatus well developed, as well as the foundations for interpretation of the observed data. We can make several sets of flight gear (See enclosure) within about a month after receipt of definite packaging details. The only other significant factors which are not presently known to us are the impedance, voltage and pulse width of our signal for modulating the transmitter.

The enclosure to Van Allen’s letter included my initial block diagram, drawings of some of the mechanical details, and data pertaining to the weights of components, permissible operational temperature range, and sensitivity to vibration.

That marked the beginning, in early 1957, of our direct participation in the col­laborative ABMA-JPL satellite effort. During April and May, in a continuing series of exchanges with ABMA personnel, we worked out further details of the satellite instrument. Stuhlinger, Joseph Boehm, Charles Lundquist, and Arthur Thompson vis­ited Van Allen, Frank McDonald, and me at Iowa City on 19 April 1957, where they provided a full description of their then-current thinking about the satellite design. The information developed at that meeting made it possible for me to send an even more detailed description of our thinking to Josef Boehm at ABMA on 3 May. My letter read, in part:

The block diagram of the cosmic ray experiment would remain as in Dr. Van Allen’s letter of February 13, and is enclosed as figure 1.

The equipment would be in the form of three units, not counting the transmitter or any power supplies.

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1. G. M. tube. Anton type 316 counter tube.

2. Module #1. G. M. tube driver and scale of 32.

3. Module #2. H. V power supply and modulator.

… The form of the modulator is not yet known, but will have to be worked out with JPL. We propose to telemeter the collector voltage of the final scaler.45

These exchanges peaked when I went to Huntsville on 10 and 11 July 1957 with portions of my then-existing Vanguard hardware and plans for an extended working session. We developed remaining details of the ABMA-JPL-State University of Iowa (SUI) collaborative satellite design, and I left that meeting with three drawings that showed the satellite’s overall physical layout and several design details. The key drawing from that session was shown earlier as Figure 7.1.

During exchanges with the ABMA people at Huntsville, there were a few tentative discussions about including our more complete instrument, including its onboard data storage as developed for Vanguard, in a second version of the satellite. That went as far as Stuhlinger’s agreement during a telephone conversation, to check into the possible use of the NRL command receiver. The idea soon died, however—there is no further mention of it in my notes.

As mentioned before, Eberhardt Rechtin from JPL visited us in Iowa City on 23 May 1957, at the same time that I was working diligently on instrument design details with the Huntsville people. He and I discussed the simple version of our satellite instrument that had evolved by that time, and details of their Microlock design.46

To this day, it has not been possible to determine whether that solo visit by Eberhardt was primarily in response to the paragraph in my letter of 1 May quoted above or whether I was being unknowingly drawn into the separate JPL effort to build their own version of a satellite in competition with ABMA. Since JPL had been a direct participant in the collaborative ABMA effort, I assumed that he was following up on my 1 May suggestion that we work out further details of our instrument’s interface with the Microlock system. I am convinced that Van Allen also believed that the Rechtin visit was part of the ABMA-JPL-SUI collaborative effort. It is entirely possible, however, that one of Eberhardt’s major objectives was to gather information about our instrument that they could use in their own satellite design. Perhaps he had both objectives. Certainly we at Iowa were unaware of the separate JPL satellite development effort, and there is no evidence that von Braun and his staff at Huntsville knew about it until November.

My next direct exchange with the JPL engineers did not occur until 22 October, when I received a call from Rechtin to set up a meeting. Discussion of that and following events is resumed in the next chapter.

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Even in Hollywood Three years after the Explorer I launch, a story appeared in the press that indicated that Hollywood nearly got into the act. A Metro-Goldwin-Meyer producer, Andrew Stone, related the story in June 1960, and it was authenticated by Lieutenant General James M. Gavin (army R&D chief at the time) and William Pickering, the JPL director. The story went like this:

Andrew Stone was commissioned by his employer in 1957 to make a movie on guided missiles. After talking to people at a number of missile research installations, he had a lengthy conversation with Pickering, and Pickering told him of the U. S. competition with the Soviets to be the first in space and that the United States could beat them by putting a satellite into space within 90 days with the army’s Jupiter C vehicle.

That energized Stone, who told him that he not only would produce the mil­lion dollars needed for the satellite but that his organization would provide four million more to buy the rocket. Pickering, recognizing that his hands were tied by the interservice rivalry, suggested that Stone take his offer to the Pentagon brass in Washington.

Stone did so, with great frustration. He could find no one in the Pentagon who seemed to be aware of the possibility. One Defense Department official told him that the job would require at least $18 million, justifying his claim by explaining that the navy had already spent that much on it.

After finally getting a firm rejection, the offer died. This occurred in May, about six months before the Soviets launched Sputnik 1.47

I left Pasadena with Henry Richter for Washington on Thursday, 20 February, to deal with the ground station readiness problem.8 Finally, on Saturday, over a week before the scheduled launch, I was on my way from Washington to Florida. After hitching a ride from the Orlando airport to Cocoa Beach with Roger Easton, Marty Votaw, and other NRL personnel, I checked in at the Sea Missile Motel. Early on Monday morning, I joined the JPL and Army Ballistic Missile Agency (ABMA) crews at Cape Canaveral and we all worked, steadily and methodically, to prepare for the second Jupiter C launch.

Being at the Cape for a full 10 days during the preparations for the initial Deal II launch attempt, I received an extraordinarily complete and exciting exposure to the myriad activities involved in launching a large multistage rocket. With the countless components that had to work together flawlessly, the handling of highly corrosive fuels and cryogenic oxidizers, and the pushing of the state-of-the-art in materials and electronics, I still marvel that it was possible to launch the first satellites at all.

270

Cape Canaveral was an isolated piece of real estate before it was tapped for its rocket-testing mission. A nineteenth-century lighthouse is still located near its tip. The few early inhabitants had to contend with swamps and myriad pests, including coral snakes and rattlesnakes, wildcats, deer, armadillos, alligators, and, of course, the always troublesome swarms of mosquitoes.

The first rocket launches from Cape Canaveral had taken place on 24 and 29 July 1950. They were of the two-stage combination of the German V-2 boosters topped by JPL WAC Corporals, the so-called Bumper rockets. They took place from a site, later identified as Launch Complex 3 but long since dismantled, near the lighthouse.

The evolution of the complete Cape Canaveral and Merritt Island area into the massive complex of today is a fascinating story in itself. The layout of the portion of the Cape that was active in 1958 is shown in Figure 10.3.

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The satellite preparations at Cape Canaveral were centered at the Spin Test Facility, located not far from Launch Complex LC-26, from which the Deal satellites were launched. The Spin Test Facility was a simple blocklike structure containing a single large bay with a high ceiling. It was built for the express purpose of stacking and checking the Jupiter C second-, third-, and fourth-stage solid rockets. The satellite received its final assembly and electrical checkout in a trailer just outside the Spin Test Facility. It was then carried into the Spin Test Facility, subjected to a payload spin test, and mated with the final rocket stage. That top assembly was spin tested, and then mated to the rest of the rocket cluster. Finally, the composite second-, third-, and fourth-stage assembly was balanced and spin tested.

The roof of the Spin Test Facility served as a wonderful observation post. It placed us in the open above the scrub growth so that we had a clear view of all launches then being conducted at the Cape. The Redstone and Jupiter pads with their blockhouses were just over a mile away. The Thor site was only one and a half miles away, and the Vanguard site was one and three-quarters miles distant. The Atlas pads were taking shape in Intercontinental Ballistic Missile (ICBM) row about four miles away. (The Titan pads shown on the map had not yet been built in early 1958.)

From the vantage point of the Spin Test Facility roof, during 1958, we observed a steady parade of launches, of both spacecraft and military rockets. This was a truly overpowering experience, even if not very wise, as we were so close that a stray missile would have been impossible to dodge. Sometime later that year, Cape officials moved the security line farther back when launches were scheduled, and we had to do our recreational watching at a roadblock somewhat farther away.

Even there, the launches were spectacular beyond words. The sense of unleashed raw power as the vehicles lifted from their pads and arched into the blue or nighttime sky was awesome, indeed. During my many visits to the Cape from 1958 through 1965, I watched launches of Bomarc, Matador, Navaho, Snark, Polaris, Juno, Thor, and Atlas rockets. Many were failures. On one occasion, I observed a particularly memorable show—an evening launch attempt of a Thor by the Air Force. It exploded only a few thousand feet into the air. The resultant burning of aluminum and magnesium parts lit the nighttime sky like a monstrous flare, so bright that objects on the ground were as clearly visible as though it were daytime.

To my great disappointment, I was never able to witness a Saturn or Shuttle launch, but by extrapolation, I can imagine the intense sensations of hearing and feeling that must be conveyed by the launch of those much larger vehicles.

Back to Deal II: the JPL satellite payload crew and I concentrated on the detailed checkout of the three identical flight instruments. Those tests included electrical performance, spin, and radiated power tests. For some of those tests, we used a

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special interrogation station set up in the nearby Atlas Radio Inertial Guidance (RIG) area. For all three payloads, I read and analyzed a seemingly endless stream of data recordings, concentrating on the performance of the onboard recorders. Although some of the tests used radioactive sources to stimulate the GM counters, others required extended periods to register the less frequent natural cosmic rays.

We also performed a major radio frequency interference test by mounting the Spare Payload atop the fully assembled multistage rocket in its launch gantry. During that test, we displayed the instrument’s signal, both in real time from the test-site receiver and post facto from data recordings made at the fully functioning ground station located some distance away. Part of that test included interrogating the onboard data recorder via the transmitter at the RIG site. Those tests worked well. Unfortunately, we were not able to spin the tub containing the three upper rocket stages and instrument atop the Redstone booster. That omission resulted in considerable anguish later, during the actual launch countdown.

On Monday and Tuesday (the two days before launch), I briefly summarized the results of the complete array of tests on all three payloads in my notebook.9 Flight Payload 1 was “no good,” with much skipping of the data tape recorder’s toothed ratchet. Flight Payload 2 and the Spare Payload were both generally satisfactorily, although there were some conditions under which the Flight Payload 2 data recorder also skipped.

It was at that time that I learned with tremendous relief that NRL had completed and tested all of their interrogating ground stations.

On the day before launch, it was time to make a final decision on the selection of the flight payload. Since Flight Payload 1 was not acceptable, it was a question of whether to fly Flight Payload 2 or the Spare Payload. Milt Brockman, the JPL payload manager, strongly preferred Flight Payload 2. It had been fully assembled and tested back at JPL, whereas the Spare Payload had been finally assembled at the Cape and had received less testing. Furthermore, a thermistor substitution had been made in the Spare Payload, and that component had not been as thoroughly calibrated. I had a slight preference for the Spare Payload, as the tape recorder operation was more dependable. I noted, “The tape recorder [in the Spare Payload] does not skip when jarred so easily. P. L. [Payload] II is quite bad in this respect. However it seems to be OK when kept still.” After lengthy discussions, I reluctantly acquiesced to Brockman’s recommendation, and Flight Payload 2 was selected for launch. That payload is shown in the photographs of Figure 10.4.

The cosmic ray experiment that led to the radiation belt discovery was the one that Van Allen first proposed in November 1954.6 Its objectives were “(a) To measure total cosmic ray intensity above the atmosphere as a function of geomagnetic latitude and (b) To measure fluctuations in such intensity and their correlation with solar activity.”

Less than a year later, on 25 September 1955, and less than two months after Eisenhower’s announced decision to include a satellite program as a part of the U. S. contribution to the International Geophysical Year (IGY), Van Allen submitted a revised and extended version of that proposal to Joseph Kaplan, chairman of the U. S. National Committee for the IGY. The first paragraph of that letter read, “There is enclosed a ‘Proposal for Cosmic Ray Observations in Earth Satellites.’ Recent discussion with Dr. G. F. Schilling has indicated that it is appropriate to submit definite proposals at this time.”7 He followed that letter with a further-expanded version that he presented at the forty-third meeting of the Upper Atmosphere Rocket Research Panel at Ann Arbor, Michigan, on 26-27 January 1956.8 The latter proposal was eventually accepted as the basis for our development of the Vanguard cosmic ray instrument.

The January 1956 proposal stated its general objective as a “study of the cosmic-ray intensity above the atmosphere on comprehensive geographical and temporal bases for the first time.” It included extended discussions of the interpretation of expected data with respect to (1) the effective geomagnetic field, (2) the magnetic rigidity spectrum of the primary radiation, (3) time variations of intensity, and (4) cosmic ray albedo of the atmosphere.

Cosmic ray albedo refers to particles that leave (splash out from) the Earth’s atmo­sphere as a result of nuclear interactions caused by primary cosmic rays crashing into the atmosphere from above. Van Allen’s paper included a figure that plotted

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lune-shaped regions in the Earth’s vicinity within which particles of particular mag­netic rigidities and traveling in certain directions might be trapped.

That drawing and its discussion reflected the fact that there had already been a substantial body of earlier study into the behavior of charged particles in the Earth’s magnetic field.9 Sightings of the aurora Polaris (aurora borealis, popularly the northern lights, in the north polar region and aurora Australis in the southern hemisphere) had been recorded for centuries. A substantial amount of theoretical and experimental work was done during the first half of the twentieth century in attempting to explain those aurorae. Many of those early studies were conducted in Scandinavia, quite naturally, since populated portions of those countries lie well within the northern auroral zone. Kristian Olaf Bernhard Birkeland (1867-1917) was one of the leading early auroral researchers and, even today, is considered one of Norway’s greatest scientists. He published the first realistic theory of the north­ern lights, including his belief that they resulted from charged particles ejected from the Sun that were somehow captured or focused by the Earth’s magnetic field.

To help prove his theory, Birkeland performed his famous torella experiment. He directed an electron beam toward a conducting sphere that had a dipole magnetic field. The sphere’s surface was sensitized, and the experiment was conducted in near­vacuum. Electrons were seen to hit the sphere primarily in two rings that suggested auroral ovals similar to those seen on Earth.

With that finding, Birkeland asked his former teacher, Jules Henri Poincare (1854­1912), to examine the motion of electrons in magnetic fields. Poincare was able to solve mathematically the problem of the motion of charged particles near a magnetic monopole. Although magnetic monopoles have not been seen in nature, his work showed convincingly that the electrons were guided toward the poles of a real dipole magnet, thus preparing the way for later work. Birkeland suggested this problem to a mathematician friend, Carl Fredrik Mulertz Stormer (1874-1957), who devoted much of his career to its further study.10

One of Stormer’s most important contributions was to show that, for electrically charged particles of various combinations of mass, charge, and vector velocity, two dynamical regions exist within a dipolar magnetic field such as that of the Earth. One is of unbounded motion, and helps to account, for example, for the arrival of particles from outside the Earth’s immediate neighborhood (from the Sun, for example) into the Polar Regions.

The second region is one containing bounded trajectories. Stormer showed that certain classes of charged particles can spiral around the magnetic lines of force and that, as their centers of motion move north or south, they are reflected by the converging magnetic field lines. Moving then toward the opposite pole, the same action takes place, and the particles continue to mirror back and forth between the poles until

CHAPTER 12 • DISCOVERY OF THE TRAPPED RADIATION 323

they are scattered by irregularities in the magnetic field or interactions with other particles.

It is clear that the early researchers tended to view the region from the outside in. That is, they envisioned the particles as approaching the Earth from the Sun and beyond, and they referred to the region of the magnetic field that we now refer to as the trapping region as the forbidden zone, i. e., a region within which particles from the outside could not enter. Although they certainly realized that a particle injected by some mechanism into that zone with the proper rigidity and direction could be reflected back and forth by the action of the magnetic field, they did not appear to harbor any expectation that there might be a substantial reservoir of particles durably trapped there.

We at the Iowa campus enjoyed a special treat during the first semester of the 1954— 1955 school year, when Sydney Chapman joined us as a visiting distinguished pro­fessor. During that semester, Chapman taught a course titled Physics and Chemistry of the Upper Atmosphere. Among other things, he included extended discussions of the aurorae, and of theories that attempted to describe them, including the works of Birkeland and Stormer. Detailed notes from his lectures were assembled by Ernie Ray as a mimeographed, unpublished compendium.11 The formal course was accom­panied by many stimulating informal discussions by Chapman, the faculty members, and us students.

Interest in the trajectories of charged particles in the Earth’s geomagnetic field, especially after the interaction with Chapman, resulted in a flurry of activity within the State University of Iowa (SUI) Physics Department. Ernie Ray and Joe Kasper undertook concentrated studies of that phenomenon. With Van Allen and others, they began to apply that knowledge to help explain the auroral soft radiation that had been detected, first on the 1953, 1954, and 1955 rockoon expeditions, and then by Carl McIlwain with his rocket shots at Fort Churchill, Canada, in 1957-1958.

In their studies, which involved tracing the charged particle motions near the Earth, Ernie made some of his earliest attempts to program the newly evolving digital computers to solve the differential equations involved. Joe configured the analog differential analyzer that he had developed for his master’s thesis for a similar purpose.

During that period, there were many spirited discussions of Stormer trajectories, cosmic ray motion, auroral mechanisms, and other related topics, both on our campus and within the larger research community. The field was abuzz with activity, both experimental and theoretical.

S. Fred Singer, as early as April 1956, suggested that the motions of charged particles in the Earth’s magnetic field, by the process hypothesized by Stormer many years

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earlier, might account for the Earth’s ring current. The ring current is an electric cur­rent, predominantly consisting of protons and heavier negative ions drifting westward around the Earth, which slightly perturbs the magnetic field at its location. Studies of the ring current had occupied Singer’s attention for some time, and that was the object of Laurence Cahill’s rockoon flights during the fall of 1957, as recounted in an earlier chapter.

Singer further elaborated on his ideas related to particle trapping in April 1957:

The [magnetic] storm decrease is produced by the high-velocity particles following the shock wave (up to nine hours later) which enter because of field perturbations into the normally inaccessible St0rmer regions around the dipole. Here they are trapped and will drift, producing the ring current which gives rise to the storm decrease. Particles with a small pitch angle, however, can reach the Earth’s atmosphere and contribute to aurora, the airglow, and ionospheric ionization.12

However, before the discovery of the high-intensity radiation by Explorers I and III, no one within the worldwide community of researchers, including Singer, had made the intellectual leap to suggest that a huge population of particles might be trapped there to form a durable region of intense radiation surrounding the Earth.

As in the case of the earlier Explorers, paper strip-charts were produced as a first data reduction step for Explorer IV, using the equipment setup shown earlier in Figure 11.4. But for Explorer IV, the process was a bit more complicated because of the highly classified nature of the Argus Project. For the initial month (before the first Argus detonation), during which all of the data were unclassified, data reduction was much as it had been for Explorers I and III.

CHAPTER 13 • ARGUS AND EXPLORERS IV AND V 377

However, during the month following the first nuclear burst, i. e. during the times that portions of the data showed the effects of the tests, Carl McIlwain served as a data screener. He diverted the charts containing indications of the Argus tests for special handling, where he served as the primary data reader.

Explorer IV results were disclosed in three steps: (1) an initial public release of the unclassified results, (2) an exchange of classified Argus data and results within a small circle of appropriately cleared personnel, and (3) a public release of the Argus results sometime later.

Work on the unclassified portion of the Explorer IV data was straightforward, even though rushed. The first tentative written expression of results was on 2 August 1958 in the form of a telegram from Van Allen.19 On the same date, the same information, with the addition of a block diagram of the instrument package, was recorded as a report in the Physics Department’s serial report series.20

Those two documents provided a very sketchy report based on the examination of only 15 station recordings from 26 through 29 July in the northern hemisphere and covering the altitude range from about 165 to 1000 miles. They reported that the instruments were operating properly and gave some very tentative information on the rapid increase in radiation intensity, as the satellite climbed above 250 miles height. Some first-ever information from Carl’s detector about the total energy density was also included.

Due to Van Allen’s, Mcllwain’s, and my heavy involvement in the Explorer IV effort, Ernie Ray was the only one from our laboratory to attend the Fifth General Assembly of the IGY Committee in Moscow on 30 July through 9 August 1958. While there, he received a telegram from us that conveyed a summary of the information from the two documents mentioned above. He presented that information at the conference.21

Additional releases quickly followed. On 20 August, a slightly expanded report based on a larger collection of data from the first two weeks of Explorer IV opera­tion was released.22 Among other things, it reported fluxes of both penetrating and nonpenetrating components, with the penetrating particles predominating at lower latitudes (in what came to be known as the inner radiation belt) and the nonpenetrat­ing particles predominating at the higher latitudes (at the horns of the outer radiation belt).

By late November 1958, our analysis had progressed far enough for us to issue a substantially expanded Department of Physics report.23 That paper included a number of interesting figures, one of which is reproduced here as Figure 13.3. The shape of the contours around 30 degrees north latitude provided a first hint of what was later recognized as the gap between the inner and outer radiation belts, with the cusp north of 30 degrees being the lower tail of the outer belt.

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FIGURE 13.3 A sketch from the 20 August Physics Department report showing initial results from Explorer IV. This is a meridional section through the Earth showing counting rates from the relatively unshielded GM counter. The data were taken between 26 July and 26 August 1958 within the longitude range west 60 to 100 degrees. (Courtesy of the University Archives, Papers of James A. Van Allen, Department of Special Collections, University of Iowa Libraries.)

The contours in that set of figures led to a speculative extrapolation of the radiation levels farther into space, reproduced as Figure 13.4. Actually, that particular model of the high-intensity radiation was one of two being considered when the paper was prepared. A second model, suggested and particularly advocated by Carl McIlwain, regarded the high-latitude cusps appearing consistently in the set of data plots to be the lower ends of a second distinct region of high-intensity radiation. Later observations from Pioneer 3 (described in the next chapter) showed Carl’s model to be the correct one.24 Since those Pioneer data were not available when the November 1958 report was prepared, the “simpler” of the two models, i. e., the one showing a single region of trapping, was chosen for publication.

The November report was presented at a meeting of the American Physical Society in Chicago in early 1959 and was published in March in the Journal of Geophysical Research}5 Since it had been actually mailed for publication late in 1958, well before the Pioneer 3 results were available, it still included this Figure 13.4, showing the single donut-shaped region of high-intensity radiation.

In addition to the variation in intensity with altitude and latitude provided in the first reports, the new paper provided information on the intensity variation with longitude, the angle of arrival of particles, and the nature of the radiation. In summary, the in­tensity varied with longitude in the way that one might expect from knowledge of the actual shape of the Earth’s magnetic field. Second, there was a strong dependence of radiation intensity on detector pointing angle. That was interpreted as indicating that the particles were moving predominantly in discs lying nearly perpendicular to the

lines of the magnetic field, thus helping to substantiate the model of particle trapping by spiral movement along the field lines. Third, although information on the compo­sition of the trapped radiation was very sketchy, electrons seemed to predominate at the higher latitudes, and there was a major proton component at the lower latitudes.

The last section in that paper, in both its November 1958 and March 1959 forms, was devoted to extended remarks on the interpretation of the data. It considered as well established that the “great radiation belt” around the Earth (by then the singular term belt was still being widely used) consisted of charged particles, temporarily trapped in the Earth’s magnetic field in Stormer-Treiman lunes. The paper went on to state that the overall decrease in intensity at the lower altitudes was almost certainly due to atmospheric scattering and collisional energy loss. Scattering would predominate for electrons and collisional loss for protons.

As to the injection rate, which would have to equal the loss rate in order to maintain a stable belt intensity, the paper stated that the decay of neutrons moving out from the atmosphere as a result of cosmic ray collisions with atmospheric molecules might

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help feed the belt, but that that source was inadequate by a large factor to produce the observed intensity. The paper asserted that solar plasma must replenish the reservoir of stored particles from time to time, working its way into the outer reaches of the Earth’s magnetic field under some conditions, and then being trapped in the magnetic field.

Finally, the paper suggested that the leakage of electrons from the trapping region at high latitudes might be the direct cause of the aurorae.