Category Dreams, Technology, and Scientific Discovery

The ground tracking and data acquisition stations did not possess equipment to convert the electrical signals into human-readable form. The first opportunity for examination of the data quality and content occurred at JPL for the Explorer I data and for the Explorer III low-power data. The Explorer III high-power data were first examined at NRL. Those activities, as explained earlier, were limited to extracting engineering data and making a cursory check on the operation of the scientific instruments. All further processing and scientific analysis for the cosmic ray data were done at the University of Iowa.

The continuously transmitted data The data arriving at our Iowa City laboratory were processed and displayed as paper strip-charts, from which our data clerks could calculate the GM counter rates. Although those arrangements were archaic when ex­amined after the passage of 50 years, they were standard practice then. The equipment and the procedures were a direct outgrowth of our experience with the balloon, rocket, and rockoon data during the early 1950s.

The ground processing equipment for the continuously transmitted data from Explorers I and III began with an Ampex tape recorder that read the data from the tapes received from JPL. Its output fed a bank of filters and discriminators that provided outputs that mimicked the signals that had been generated by the sensors on the satellite. Those outputs were converted to inked traces on the continuously moving paper charts.

Figure 11.4 shows the equipment setup as it existed in late 1958. The seven-track Ampex tape playback unit in the second rack from the left had been added by that time. The camera recorder extending from the panel on the far right was installed to handle the data from the onboard recorder in Deal II. The full equipment lineup

310

shown here was also used during that summer to process the Explorer IV data, as detailed in Chapter 14.

An example of one of the charts made to show the Explorer I high-power data is shown in Figure 11.5. Channel 4, carrying our cosmic ray data, displayed a complete cycle (positive, to negative, and back to positive) for every 32 particles that had been detected by the GM counter.

This figure also shows the cylindrical shell and transmitter temperature data from channels 1 and 2, respectively, and the micrometeorite microphone data on channel 3. The engineers at JPL read a similar chart to determine that the shell temperature (in this sample) changed from 22.5 to 21.0 degrees centigrade, while the transmitter temperature remained steady at 34.5 degrees. Also from the comparable JPL chart, the AFCRC scientists determined that the microphone did not register more than three hits during that pass, since no transition occurred in the output of the factor-of-four scaler that followed the microphone.

Similar charts were produced for the data from the low-power transmitters on both Explorers I and III. On those charts, channels 1,2, and 3 displayed the front cone skirt temperature, front cone tip temperature, and number of severed micrometeorite grids,

FIGURE 11.5 A portion of a SUI paper strip-chart displaying data from the high-power transmitter in Explorer I. These data were recorded on 4 February 1958 at the Microlock station at Patrick Air Force Base, Florida. The time trace at the bottom of the chart indicates that this segment started 14 seconds before 0241 LIT and covered a total period of 111 seconds. The two vertical lines represent the approximate beginning and end of usable cosmic ray data from that pass. (Courtesy of the University Archives, Papers of James A. Van Allen, Department of Special Collections, University of Iowa Fibraries.)

OPENING SPACE RESEARCH

respectively. The low-power system cosmic ray data and time markers were identical in form to those shown in Figure 11.5 for the high-power systems.

Since we used the temperature measurements read by JPL, and had no responsibility for the micrometeorite data, our focus was fully on the channel 4 cosmic ray data and time markers. As a rule, we processed the data from only one of the transmitters for each station pass. In the few cases where both signals were recorded (primarily at the JPL and PAFB stations), we used the better of the two.

The Explorer III onboard recorded data Handling the data from the recorder in the Explorer III satellite instrument package presented a completely different challenge. For a typical operational sequence, the ground station operators prepared for a pass by pretuning their receivers, pointing the antennas in the direction where the satellite was expected to appear, and starting the ground recorder for the low-power signal ahead of time. Arrival of the satellite on the horizon was announced by the appearance of an initially noisy signal from the low-power transmitter. Of course, there was no signal from the high-power transmitter, as it had yet to be turned on.

As the satellite rose above the horizon, the signal from the low-power transmitter became stronger and clearer. The antennas for both the low – and high-power signals tracked the satellite as it progressed across the sky. When the antennas reached a reasonable height above the horizon, and as the low-power signal became sufficiently clear, the operator started the ground recorder for the high-power signal and then transmitted a command to the satellite to turn on the high-power transmitter. If all had been set up properly, the command resulted in the immediate appearance of a signal from the high-power transmitter. After two seconds, the onboard tape recorder began its playback. For occasions when the onboard recorder had stored a full orbit’s data since its last interrogation, its readout took about six seconds. When the tape readout was complete, the transmitter turned off, and the onboard system reset itself to record the next orbit. Thus, the entire readout operation occurred typically within a brief eight-second interval.

The ground station tapes were annotated during recording with voice announce­ments and timing markers, and handwritten comments were entered by the operators in the logs.

The pulses during the brief burst of data appeared at a rate of about 1000 per second. The task in the Cosmic Ray Laboratory’s processing facility was to pick out the burst of information for each pass and to display that information in usable form. Two techniques were employed.

The first, valuable for a quick look at the general form of the data, was to record the signal on another moving pen strip-chart recorder, similar to that being used for the low-power data. Since the pulse rate was somewhat beyond the frequency response of the chart recorder, the traces were distorted, and it was not possible to count the

individual pulses from that source. The charts did convey, however, a very distinctive pattern to trained data readers. As it turned out, once the data blanking due to the high-intensity radiation was understood, those quick-look charts were invaluable in delineating the extent and location of the radiation belt, as described in detail in the next chapter.

The second method for reading the Explorer III onboard tape recorder data used a special camera that had been constructed for the purpose. That camera is shown on the far-right rack of equipment in Figure 11.4. It displayed the received signal on a small cathode ray tube, which had a frequency response far beyond that needed to follow the data traces. Seventy millimeter film moved vertically past the horizontal trace on the cathode ray tube. Thus, the pulses were arrayed along the length of the film, as illustrated in Figure 11.6.

It has generally been believed that the Navy’s Vanguard and Army’s Jupiter C programs were the only two active U. S. satellite programs in early 1958. There was actually a third one, but it was so secret that information about its existence did not surface until much later. Certainly we knew nothing about it at Iowa. Not even the Navy officials who were building Vanguard were aware of it.

The program was conceived and carried out by physicists and engineers at the Naval Ordinance Test Station (Naval Air Weapons Station) located at China Lake, a dry lake bed southwest of Death Valley National Park, California. After the Sputnik 1 launch, a number of the physicists who were then working on the Sidewinder missile came up with the idea of launching satellites via a small multistage rocket from an aircraft. At first, the idea was carried out sub-rosa using limited internal research funds, but in November 1957, the idea was exposed to the Navy’s Bureau of Aerospace and Bureau of Ordinance in Washington. Very limited start-up funding was approved in February 1958. The effort came to be known as project Pilot officially, but as NOTSNIK by the participants. NOTS stood, of course, for the Naval Ordnance Test Station, and NIK was borrowed from Sputnik.8

The satellite payload was a very small one, even by Explorer I standards. The pack­age was eight inches in diameter and weighed only 2.3 pounds, with the electronics arranged in the form of a donut. It was to be launched by a Douglas F-4D1 Skyray aircraft at a launch altitude of about 12,500 feet, at a speed of 450 miles per hour, and with a climbing angle of 50 degrees. It was planned that after separation from the aircraft, the first pair of Hotroc motors (a derivative of the Subroc antisubmarine missile) would be ignited. Five seconds later, the second pair was to be ignited, placing the payload with its final stage into a transfer trajectory. Half an orbit later, the final stage was to be fired to put the payload into a near-circular orbit. The all solid-stage rocket assembly was designed for maximum simplicity, with no moving parts.

The earliest conceived mission for the NOTSNIK satellite was for either military reconnaissance or weather observation, or both, depending on which report one reads. Its original sensor was a small infrared camera, designed to take images of the ground or weather patterns. Even though its ground resolution was only about one mile, it was still feared that the satellite might have been construed by the Soviets as a reconnaissance satellite, and therefore contrary to the U. S. desire to avoid emphasizing the military uses of space. Thus, the project was classified Top Secret and remained so for a considerable period.

As the Argus Project began to take form, NOTSNIK gained a more concrete mission—to be part of the Argus observational network. For that mission, its sensor was changed to a radiation detector. Circumstances, however, established a nearly impossible schedule. Two ground test launches and one air test launch were made

CHAPTER 13 • ARGUS AND EXPLORERS IV AND V 365

during July 1958, of which the ground launches resulted in vehicle explosions. After the first air launch, radio contact with the satellite instrument was lost, and it was never determined whether the instrument might have gained orbit. Two more ground launches were made during August, but both failed due to structural failures of the fins shortly after takeoff. Air launches in direct support of Argus were attempted on 12, 22, 25, 26, and 28 August, but none resulted in verifiable satellite orbits.

After that record of performance, the project had a sporadic life, finally dying after several different incarnations. The basic concept lived on, however, leading to the highly successful Pegasus project which also involved rocket launches from aircraft. The first Pegasus launch took place in April 1990, and by April 2008, 34 successful Pegasus launches have been made.

Iowa City was a rather small city. As the university’s program for exploration with balloons and rockets developed in the early 1950s, the local media took an increasing interest in the work. It enjoyed growing coverage in the Iowa City Press Citizen, the university’s Daily Iowan, the Cedar Rapids Gazette, the Des Moines Register and Tribune newspapers, and local radio stations KXIC and WSUI.

I enjoyed a unique outlet. Dad had a radio program over station KXIC six mornings each week. Although it focused on rural news and events, his natural interest in science and his pride in his son’s rocket and satellite work led to my appearance on his program on a fairly regular basis.

As the time for the opening of the IGY approached, there was a growing public awareness that entry into space was near at hand. As our cosmic ray instrument began to take visible form, more and more articles appeared to describe our work.4 In mid- 1957, there was a flurry of activity in the local press as our instrument package neared its final form.

Through lectures at service organizations, teachers’ and other professional con­ferences, industrial companies, and other universities and colleges, we described our evolving work to a wider audience. I even described the Vanguard program to a small group of farmers at a plowing match where I stood on a wagon to describe the prototype instrument. Many years later, I received a letter of thanks from one of that day’s attendees. He stated, “Your presentation enabled… us to avoid the paranoia that surrounded Sputnik armed with the confidence that our side was working on a satellite which would be more sophisticated than that of the Russians. Our confidence was well placed.”

Van Allen was, naturally, the focus of much of that attention. Our satellite launches and the discovery of the Earth’s high-intensity radiation belts thrust our campus group into the national and international scientific and public spotlights. To cite only a few examples of the coverage, Life magazine reporters interviewed Van Allen and took pictures of our handiwork on 9 May 1957 for major coverage in their magazine. On the occasion of the Explorer III launching on 26 March 1958, the Cedar Rapids Gazette featured an article on its front page that proclaimed, “A Son and a Satellite for SUI’s Ludwig.”5 At the end of March, a CBS television crew arrived, and Walter Cronkite interviewed Van Allen for his news broadcast. And so it continued throughout the rest of the time that I was in Iowa City.

Admittedly, I reveled in all the attention.

During the late 1940s and early 1950s, important advances were made in balloon technology. Large balloon development received a major boost at the Instrument Division of General Mills in Minnesota, Minneapolis. That work was spearheaded by Otto Winzen, Jean Piccard, and others. The ONR supported the developmental work and many flights over a period of years. Those large balloons were known from the beginning as Skyhook balloons.

The University of Minnesota Physics Department was an early adopter of balloons for cosmic ray research. In 1948, they employed them to loft nuclear emulsions and a cloud chamber to make the important discovery of heavy cosmic rays. In late 1949, John R. Winckler arrived and joined the cosmic ray program. Key graduate students associated with that early work included John E. Naugle, who went on to serve with great distinction as a senior official in NASA Headquarters. They also included Frank B. McDonald and Kinsey A. Anderson, both of whom later joined the SUI faculty.

In 1952, frustrated by a number of unexplained early balloon failures, Minnesota scientists Charles Critchfield, Edward Ney, and John R. Winckler undertook a then – classified military project to improve balloon performance. Their primary motivation was to develop a system that could photograph military installations in the Union of Soviet Socialist Republics (USSR). Although development of the U2 reconnaissance aircraft supplanted the need for such a balloon system, a number of the techniques worked out in that program were applied to cosmic ray and other high-altitude atmo­spheric research.12

Two key developments in that developmental project made very large balloons possible. The first was the “natural shape” balloon configuration, in which the inter­nal pressure of the balloon-lifting gas was spread out over the envelope by a network of load-bearing meridional tapes, thus keeping the circumferential stresses within tol­erable limits. The second key improvement was the “duct” appendix. Earlier balloons had been vented at their bases to permit them to valve their excess gas at ceiling altitude. That, however, permitted the premature admixture of air into the balloon envelope, and the balloons would not remain for long at their peak altitude. The new approach used a duct that extended from the base to well up within the gas envelope, so that venting could occur without diluting the lifting gas.

OPENING SPACE RESEARCH

Frank B. McDonald was one of the University of Minnesota cosmic ray researchers who profited greatly from these developments.

his chapter addresses the development of the cosmic ray instrument for the Van­guard satellite program at the University of Iowa. It covers the period from the experiment’s first proposal in 1954 until the launch of Sputnik 1 in October 1957. The launch of the Soviet satellite resulted in a major shift in the Iowa program.

At that point, the decision was quickly made for the army to proceed with a parallel satellite program using their Jupiter C-based launch vehicle. A small portion of the Vanguard instrument that is described in this chapter was extracted to form the very simple primary scientific instrument launched in January 1958 on Explorer I. The full Vanguard package that is described here, with some minor modifications to adapt it to the different launch vehicle and the expanded network of ground receiving stations, was successfully launched shortly thereafter as Explorer III.

Although the instrument was certainly simple by today’s standards, it did mark an important step in the evolution of remotely operated robotic devices in a new en­vironment. Some of the details of this instrument’s architecture and circuit design have been previously described.1 However, an account of the elaborate process of instrument development, testing, and launch, including the many special problems that were encountered, has not been previously available.

Those not interested in the many technical details of developing an early scientific instrument for use in space may want to read the opening sections of this chapter and then move on to the account of the first Sputnik launch in the next chapter.

125

OPENING SPACE RESEARCH

Shortly after the final decision to go the Vanguard route was announced on 9 Septem­ber 1955, the secretary of defense directed the army to stop “all satellite-related study, research, development, and design work” and concentrate on its primary mission, the development of military missiles. With that order, the Huntsville and Pasadena groups lost all official support for further government-funded work on their satellite activities.

Many at Huntsville, Pasadena, and elsewhere (including Van Allen at Iowa) continued to harbor serious misgivings about the Vanguard decision. They be­lieved that the army’s Redstone-based Jupiter C, being much further along in its development, would provide greater assurance of meeting the IGY schedule and objectives.

Thus, although the Orbiter name could no longer be mentioned externally, the basic concept did not die at the working level. Behind-the-scenes actions were undertaken during the next two years to keep that option open. That work continued on three fronts: at the ABMA at Huntsville, at JPL in Pasadena, and at the University of Iowa in Iowa City.

At the Army Ballistic Missile Agency A few days after the decision to commit the United States to the Vanguard approach, General Simon of Army Ordnance registered an angry protest. He asserted that, by fitting the Redstone with the larger scaled-Sergeant upper stages, they could launch an 18 pound satellite as

OPENING SPACE RESEARCH

early as January 1957. However, the navy’s Vanguard contractors—General Electric, Martin, Aerojet General, and Thiokol Chemical—responded with their own assur­ances of quick action, and Simon’s plea got nowhere.19 20

Homer Stewart, who had chaired the committee that had recommended Vanguard, believed that the Vanguard decision was a grievous mistake. Soon after the decision, he traveled to Huntsville, accompanied by JPL director William Pickering and their close associate, Jack E. Froehlich. Their purpose was to discuss how the Orbiter concept might be kept alive. At that meeting, Pickering committed to the use of the JPL scaled-Sergeant rockets as a substitute for the smaller Loki upper-stage rockets to increase the satellite weight capability. In addition, he offered his laboratory’s help in other ways, including use of the supersensitive Microlock telemetry and tracking system that had been developed under Eberhardt Rechtin’s leadership, and with satellite instrumentation, tracking operations, and ground data handling.

Out of those discussions came what they believed to be a “bullet-proof” plan. The RTV that was needed by the Jupiter missile program would be an adaptation of the Orbiter concept. It would be built in such a way that it could be used as a satellite launcher with only minor modifications.

Von Braun called a meeting of his senior staff soon after that meeting. He arrived with his usual beaming smile, saying:

They stopped us in the tracks with our satellite, but we are still in business with our reentry tests. Let’s go to work right away! We will build the upper-stage system for the testing of Jupiter nose cones, which we have been preparing since 1953, and we will launch the first Jupiter C next year, as planned. This will be perfectly legal. In fact, we have to do this anyway for our Jupiter missile project. At the time when we will be called upon to launch a satellite—and I’m sure that time will come—we will quickly add that third solid rocket stage, modify the guidance system, put the satellite on top, and we are in business, and even without transgressing the limitations they have clamped on us!21

When it became clear that some of the 12 Jupiter C test vehicles would not be needed for the nose cone-testing program, von Braun made another noteworthy decision. As reported later by Stuhlinger:

With tongue in cheek, von Braun decided that one of the Jupiter C vehicles should be set aside and carefully subjected to a “long-time storage test”; it was quietly understood that this vehicle represented a potential satellite launch rocket. As soon as permission could be obtained, that vehicle would be taken out of storage, and a third Sergeant stage, an attitude orientation system, and an ignition command receiver would be added. In a parallel action, Jack Froehlich at JPL put a number of [scaled] Sergeant rockets into a controlled environment “to study long-time effects on the propellant,” just in case.22

The master plan and schedule for the fully sanctioned RTV program was prepared jointly by ABMA and JPL in August 1955. The first nose cone reentry test flight was set for September 1956. They tacitly agreed that they could be ready for a first satellite

CHAPTER 7 • THE U. S. SATELLITE COMPETITION 195

launch about a year and a half after that first nose cone test, believing that that would provide sufficient lead time to avoid any conflict with their other programs.

Terminology has sometimes been confusing. Orbiter was the original designation for the four-stage satellite launcher. After the Orbiter project was officially set aside, Jupiter C denoted the multistage Redstone-based configuration, both the three-stage version used for nose cone testing, and, behind the scenes, for the four-stage version used later for the Explorer satellite launches.

The Jupiter C developed for the nose cone testing was also referred to as the RTV. That term was eventually applied to the satellite-launching version, as well. That was especially true during the satellite launch preparations at Cape Canaveral, when it was desired to create a public perception that just another regular Jupiter test launch was in progress.

After the launch of Explorer I, the satellite launcher was frequently referred to as Juno (eventually Juno I) to provide a softer connotation than the perhaps somewhat bellicose-sounding Jupiter name. In Roman mythology, Juno was the sister and wife of Jupiter, god of the sky.

Thus, Orbiter, Jupiter C, RTV, and Juno I have all been used from time to time to identify the Redstone-based satellite launcher. Within the proper context, all are correct.

The Juno name persisted beyond Juno I. Juno II used the Juno I spinning tub arrangement for the upper stages, but the Jupiter rocket was substituted for the Redstone as the first stage to provide a greater payload capability. Any use of the Juno III designation has been lost in obscurity. However, Juno IV was a Huntsville designation for an early concept for the Saturn I and IB, and Juno V referred to an early Saturn V concept.

Following the decision to go with Vanguard, the army continued to send technical information to the Vanguard project office in Washington. Von Braun and his repre­sentatives repeatedly offered to join forces with the Vanguard team. They suggested that a Vanguard satellite could be launched on top of a Redstone rocket, and went so far as to offer to launch the NRL-designed satellite under the Vanguard name, including painting the word Vanguard on the rocket’s side. Stuhlinger carried that offer separately to the Pentagon, to John Hagen (Vanguard project manager), and to Milton Rosen (Vanguard chief engineer). In all three cases, the answer was, “No, thanks.”23

In May 1956, the assistant secretary of defense (R&D) requested of the special assistant for guided missiles in the office of the secretary of defense that ABMA’s Jupiter C be supported as a backup to the Vanguard rocket. The response was that no such plans or preparations would be undertaken without indications of serious

OPENING SPACE RESEARCH

difficulties in the Vanguard program. As those difficulties did not openly surface until later, the request was denied.

On 1 February 1957, in response to a request from the Department of the Army, ABMA responded that the army Jupiter C could accommodate the scientific instru­ments being built for the Vanguard but not the large Vanguard sphere. The instruments could be repackaged fairly simply into a cylindrical configuration to fit the Jupiter C vehicle.

A few months later, in April, ABMA proposed to the chief R&D of the Department of the Army that it orbit, as a backup to Vanguard, six 17 pound satellites with the Jupiter C vehicles. They promised that the first of those would be orbited by September 1957. On 7 May, the Department of the Army formally responded by reiterating that there were no present plans for backing up Vanguard.

As a part of the continuing technical exchange between the ABMA and NRL efforts, General Medaris sent an ABMA satellite capability report to Vanguard’s Hagen in late May or early June 1957. However, on 21 June 1957, the Department of Defense, in the form of a personal visit by their General O’Meara, instructed General Medaris in no uncertain terms that ABMA’s mission was missiles, not satellites. As a result, Medaris felt compelled to recall this ABMA report from the Vanguard office. He later stated in a 1958 congressional inquiry (when the Congress was investigating the U. S. failure to beat the Soviets into space) that “in various languages, our fingers were slapped, and we were told to mind our own business, that VANGUARD was going to take care of the satellite problem.”24

Because of those rejections, and of the direct order to cease satellite work, von Braun felt compelled by mid-1957 to back off on his continuing efforts to obtain Defense Department support for their satellite launcher. Ernst Stuhlinger did not feel quite as constrained. In view of the continuing hints of Soviet progress toward launching a satellite, he attempted yet another appeal in late September. He went first to von Braun, who, stung by the repeated admonitions to stick to their primary mission, quipped, “If you wish to become nervous, do so—but leave me out! I cannot move anyway, as you well know!”

On 27 September 1957, only seven days before Sputnik 1 was launched, Stuhlinger again appealed to ABMA director General Medaris, stating his conviction that the Soviets were close to orbiting a satellite. “A Russian satellite [he said] will soon be in orbit. Wouldn’t you try once more to ask the Secretary for permission to go ahead with our satellite? The shock for our country would be tremendous if they were first into space!”25 Medaris’ reply was, “Now look, don’t get tense. You know how complicated it is to build and launch a satellite. Those people will never be able to do it! Through all my various intelligence channels, I have not received the slightest indication of an impending satellite launch. As soon as I hear something, I will act.

CHAPTER 7 • THE U. S. SATELLITE COMPETITION 197

When we learn something about their activities, we will still have plenty of time to move. Go back to your laboratory, and relax!”26

A week later, Sputnik 1 was repeatedly crossing our heavens with its incessant “beep-beep!” At that point, von Braun asked Stuhlinger, “Did the General talk to you since it happened? I think he owes you an apology!” “Yes,” was the answer. “All he said was: ‘Those damn bastards!’”

During the next two days, news coverage of the event swelled across the country and throughout the world, as editors and reporters rushed to provide their readers with a basic background in rocketry and endless details of the momentous event. Although newspaper coverage was rather sparse in Saturday’s morning papers because of the timing, the afternoon papers were dominated by the news.

In the Sunday morning editions, the press had a field day. Papers across the country devoted much of their front pages to coverage of the event. The New York Times headline read16:

U. S. SATELLITE IS “WORKING NICELY”; Army Ordered to Launch
Another; Also Plans Reconnaissance “Moon”

That paper devoted a substantial number of full pages to coverage of the event.

Not surprisingly, the Florida newspapers were especially effusive. The Tampa Sunday Tribune headline read17:

U. S. SATELLITE WHIRLS 1700 MILES UP

The edition carried 26 different stories covering the event, plus nine pictures, drawings, and cartoons. The articles covered everything from technical details to speculation about future launches.

OPENING SPACE RESEARCH

To illustrate the editors’ obsession with covering the event adequately, one of the paper’s articles was headed:

Florida Roach May Be On New Earth Satellite

It read, “Dr. Richard Porter, a top satellite scientist, was briefing reporters early today on the success of America’s first satellite, Explorer. One reporter wanted to know whether Explorer carried any living matter on the flight into outer space. ‘Not intentionally,’ Porter replied. ‘But maybe a Florida cockroach climbed aboard.’ ”

It was decided by the powers in Washington that our first satellite should be known as Explorer, and the less elegant name Deal passed into obscurity. Many project participants lamented the loss of the satisfyingly uncomplicated name, but the new name was quickly adopted. The Explorer name continued for many years to denote a class of relatively small Earth satellites that pioneered many advances in exploratory space science. Explorer 90 (also known as AIM) was launched on 25 April 2007.

Explorer I with its attached rocket stage was 80 inches in length, of which 34 inches comprised the satellite itself and 46 inches was the final rocket stage. Both the rocket stage and satellite payload were six inches in diameter. The total weight placed in orbit was 30.80 pounds, of which 10.63 pounds was the satellite instrument, 7.50 was its shell, and 12.67 pounds was the exhausted final rocket stage.

The initial orbit ranged from 221 miles height at perigee to 1583 miles at apogee, with an inclination relative to the Earth’s equator of 33.3 degrees. The initial orbital period was 114.7 minutes. The satellite reentered the Earth’s atmosphere on 31 March 1970.

Once the data were recorded as described above, the truly laborious handwork began. Students were employed as part-time aides to read the charts and filmstrips.

For the paper charts recorded by the multitrace pen recorders, data reduction involved first measuring the distances from the beginning to the end of clusters of several cycles of the GM counter scaler output with a ruler. Then the corresponding time intervals were measured, and the GM counting rates were computed from those two numbers. Figure 11.7 shows some of the data readers at their task.

For Explorer I, the counting rates were tabulated, along with the satellite orbital positions that had been computed by the Vanguard Computing Center in Washington, D. C. Eventually, we produced a master tabulation of the Explorer I GM counter rates for all periods during which successful ground station recordings were obtained.32

314

The immensity of the effort required to assemble that tabulation cannot be over­stated. Seventeen ground stations recorded data over the active period of Explorer I operation. That produced a collection of more than 1000 tapes covering the period from 2 February to 16 March 1958. Since the stations started their tape recorders shortly before each scheduled satellite transit, some of the recordings did not contain usable data, because either the station was unable to acquire the signal for some reason or the received signal was too faint and noisy to be useful. Six hundred and fourteen tapes, however, did provide readable signals and were fully processed by the data readers.

That Explorer I tabulation represents a unique record of cosmic ray data above the atmosphere for that period. The document contains an introduction that includes the GM counter calibrations and descriptions of the tables. The second section of 105 pages contains a listing of all recordings. The actual data tables occupy the third section of 824 pages. Each page of the data tables contains from 1 to 28 entries. Some passes were long enough that their data spanned up to four pages. It is estimated that there are more than 12,000 individual data entries in this master tabulation, each with its nominal time, time interval, count, rate, geographic latitude and longitude, and height. In addition, each page contains appropriate general information, such as the station, record number, date, time base correction, and beginning and ending times of the pass, plus the names of the data readers and checkers.

CHAPTER 11 • OPERATIONS AND DATA HANDLING

The data readers exercised their judgment in discriminating, on an inch-by-inch basis, the distinction between data, noise, and other artifacts. Each data interval was measured with a ruler by a reader, then independently by a data checker. In cases of conflicting or other questionable results, a third person, and in some cases a fourth person, checked the readings.

The entire data reading effort was supervised by Anabelle Hudman, an outstanding research assistant who had that as her primary responsibility. The dedicated and long – suffering individuals who read and checked the Explorer I data were, in alphabetical order, as follows:

K. Atit

S. Clendenning C. Horn S. Hwang H. E. Lin W. C. Lin

M. Thornwall M. Van Meter J. Von Voltenburg S. Yoshida A. Zellweger

Sekiko Yoshida was a visitor to the department, on leave of absence from the Department of Physics, Nagoya University, Japan. During her time at Iowa, she was a valued member of the research staff and contributed substantially to the research effort. Wei Ching Lin was a physics student who went on to complete his own research projects, earning his M. S. and Ph. D. degrees in 1961 and 1963. Hseh-Er (Lucy) Lin was his wife. The rest were other students in various campus departments, or spouses of such students.

No account of that huge effort would be complete without a special tribute to the remarkable effort of Evelyn D. Robison in typing the tabulation. At the time, she was a secretary in the Physics Department office and typed all 929 pages on a standard manual typewriter. In hours of poring over the document, I have never seen an error, or even a correction. She was a truly remarkable helper and went on to serve as Van Allen’s devoted personal assistant for three decades.

A few portions of the strip-chart recordings from the Explorer III low-power system were read in a similar manner. However, completion of that effort was overtaken by events. By then there was the realization that a region of unexpected intense radiation existed in space. The Explorer III onboard tape recorder turned out to be ideally suited for examining that phenomenon, and our full attention immediately shifted to reading those data. Further discussion of the reading of the onboard stored data is contained in the next chapter.

It is emphasized that all of this work was done before electronic computers were in general use. We did have access to an IBM 650 computer, which used a combination of

OPENING SPACE RESEARCH

punched cards and patch panel programming. It was limited to 2000 words of storage on a magnetic drum, and the programs were written in Fortransit. That computer was not in routine use for satellite data processing until at least the summer of 1959.33 Although the campus did acquire a series of early large-scale computers during the late 1950s, their punched-card, batch-processing mode made them not very effective for this task.

Initial thinking about the Argus Project was well advanced within classified circles before the mid-March meeting at JPL. Although none of us at Iowa knew of Argus planning by then, we subsequently became aware of it by degrees.9 Faint suspicions of a nuclear testing connection might have been in Van Allen’s mind from the time of that meeting, but it was not until the following weeks that he learned of the activity in any comprehensible terms. During those weeks, Van Allen kept Panofsky updated on Explorer I satellite results by phone and became increasingly aware of the Argus planning.

I made a short stop at Iowa City on 29-30 March following the Explorer III launch. During our get-together, Van Allen shared some of the Argus thinking with Carl McIlwain and me, and we, collectively, began thinking about instrumentation that might support that project, as well as advance our investigation of the naturally occurring radiation. That evolving situation was a major reason for my hasty return to the Iowa campus from my five-month employment at JPL.

Immediately following those discussions, on 31 March, Van mailed Panofsky detailed information about the Explorer III detector and orbital parameters. Since the Explorer I data were not yet understood, and as we had not yet seen any Explorer III data, he made no mention in that letter of observational results, including any hint of the anomalous high-intensity readings.10 Van Allen continued telephone discussions with Pickering and Panofsky during the following week, during which time he first mentioned our growing belief that we were seeing particles trapped in the Earth’s magnetosphere. During those discussions, Panofsky suggested that the high-intensity radiation might have been injected artificially by the Soviets.11

On 9 April, while I was driving back to Iowa City from Pasadena, Van Allen wrote a letter to Panofsky (with copies to Herbert York and Pickering), which contained the first known written reference to our new discovery. Knowing of Panofsky’s suggestion

OPENING SPACE RESEARCH

that the belts might have been produced by the Soviets, Van opened his letter, “It appears that nature (or the Soviets?) may have ‘done us in’ insofar as the contemplated observations [from the Argus detonations] are concerned.”12

We learned later that the Soviets, after first hearing of our trapped radiation dis­covery, thought that the belts that we were observing might have been caused by U. S. high-altitude nuclear bursts. That suspicion, and the reciprocal suspicion by U. S. scientists, was eventually dispelled.

When I arrived back in Iowa City on 11 April, I went immediately to the campus for an updating and strategy session. Discussions between Van Allen, Argus Project personnel, Carl, and me progressed rapidly from that point on. Carl began working on detector designs for what became Explorer IV, and I began laying out its overall system design.

I produced a first complete design layout for the new Explorer IV instrument on 18 April. It included a block diagram showing the array of detectors on which Carl was working and an overall arrangement for the detectors, scaling circuits, and telemetry electronics. It also included a first drawing of the physical arrangement of the instrument package, a listing of its power requirements, and an estimated weight breakdown.13

That information was presented as a specific new satellite proposal by Van Allen at a planning meeting in California the following week. He recommended two GM counters and one counter using a photomultiplier tube to detect the light pulses from a plastic scintillator. The later counter would help differentiate between the natural radiation and radiation produced by the nuclear bursts. A second scintillation detector using a thallium-doped cesium-iodide scintillator was added by Carl soon after to register the total energy deposited in the crystal.

That pivotal California meeting resulted in agreements between Van Allen, JPL and Army Ballistic Missile Agency (ABMA) personnel, Argus personnel, and others on the overall form of the satellite, schedules, and the assignment of responsibilities.

It was at that California meeting that Van Allen rather matter-of-factly stated that we, at Iowa, were prepared to build all the payload instruments. That proposal was accepted with little debate, and Van wrote enthusiastically in his notes, “Agreed: [Iowa] will coordinate payload assembly.”14 That decision resulted in an arrangement whereby the overall payload was designed and assembled at Iowa.

Van Allen called me from California with that news, and with schedule information that would stretch Carl, me, and our helpers to our limits. It called for having a photomultiplier tube in a suitable mounting ready for a vibration test on 3 May, just nine days hence. We were to deliver a full prototype satellite to Huntsville for design approval testing on 1 June and four complete flight payloads on 1 July.

CHAPTER 13 • ARGUS AND EXPLORERS IV AND V 367

Van Allen traveled from JPL to Washington, D. C., for further project coordination and other matters. He remained there for most of the following week. On Saturday, he called to discuss a variety of project issues, including the fact that Stuhlinger at Huntsville was quite anxious to work directly with us on the project, rather than through JPL. That eventually resulted in a working arrangement in which we built the full instrument package at Iowa, and the Huntsville people coordinated the interface between the payload and the launch vehicle, performed tests on the satellite that we were not equipped to do in Iowa City, made the launch arrangements, and conducted the launch operations. That arrangement worked wonderfully well.

It was also during the meeting at JPL that Van Allen obtained agreement that the satellite’s orbital inclination would be 51 degrees. That was compared with the 33 degree inclination of the Explorer I and III satellites. We wanted the inclination to be as high as possible so that the new satellites would sample radiation over as much of the region between the north and south auroral zones as possible. Furthermore, a high inclination was needed for observing the Argus Effects. The agreed-upon inclination of 51 degrees was the highest inclination possible for a launch trajectory from Cape Canaveral that would not pass over heavily populated areas.

Although we were already progressing rapidly with actual hardware design, formal approval of the Argus Project, and of our involvement in it, took a little more time. It was on 28 April that Van Allen informed me that we were receiving preliminary funding. The next day, ABMA received a verbal OK from the Advanced Research Projects Agency for their participation in Project Argus and for the State University of Iowa (SUI) role.

The first of May was a hugely eventful day on two fronts—Van Allen announced our high-intensity radiation discovery to the world, and the Argus Project was formally (very quietly) approved.

Immediately following the Explorer I launch, while stepping away from the Explorer I data analysis at Iowa City to continue with the Deal II instrument preparations at JPL,

CHAPTER 16 • SOME PERSONAL REFLECTIONS 439

I was in the midst of a major shift in focus. When I started at the university in 1953, it had been as a physics student, and I took my bachelor’s and master’s degrees in that field. When I undertook the satellite project in 1956 as my graduate research topic, Van Allen and I clearly anticipated that I would develop and prepare the instrument, oversee its launch, and be a major player in processing and analyzing the data and publishing the scientific results.

The decision to switch our experiment to the Army launcher following the Sputnik 1 launch changed that plan. Our agreement with JPL included launching our instrument in two steps. As described earlier, a simple version was launched first in the interest of programmatic speed. That was followed by the launch of our full instrument. Thus, the first U. S. space data were arriving at Iowa City while I was still preparing the second instrument at JPL.

Naturally, we all wanted the Explorer I data to be examined as quickly as possible. Ernie Ray assumed the responsibility for processing the data. Carl McIlwain soon arrived back on campus from his Fort Churchill expedition, and with great enthusiasm and energy, the two of them and Van Allen set about to uncover what that spaceborne Geiger-Muller counter had to report. For the first two and a half months after the Explorer I launch, it was necessary for me to follow that effort from a distance.

A few months later, that situation was prolonged, when the enthusiasm resulting from the successful Explorer I and III flights led to quick approval of the Explorer IV, Explorer V and Heavy IGY Satellite programs, and I had to concentrate on the development of those instruments. Thus, the succession of events led me increasingly away from physics and toward engineering.

The shift soon showed up in my academic progression. At the beginning of the spring 1959 semester, I signed up for the last of the mainstream physics courses that were needed for a Ph. D. degree. Those were highly abstract courses in Quantum Mechanics (being taught by Fritz Coester), Nuclear Physics (taught by James Jacobs), and Relativity (offered by Fritz Rohrlich). They did not come easily for me and, frankly, were outside my area of strongest interest. They were requiring a tremendous effort, when my time was being consumed relentlessly by the satellite instrument development in which I reveled.

At the same time, I realized that a wealth of interesting course work was being offered across the street within the Electrical Engineering Department. Consequently, in the middle of that spring semester, I dropped my physics courses and picked up upper-level courses in Electrical Transients and Pulses (taught by Lawrence A. Ware) and Active Networks (offered by Professor Streib). During the next few semesters, in addition to the standard advanced engineering courses, I set up and pursued sev­eral individually tailored courses to cover topics of special interest. One of those was a course in Radio Telemetry. I studied the topic using the text by Nichols and Rauch6 and then “taught” it to Professor Streib in a series of weekly one-on-one sessions.

OPENING SPACE RESEARCH

Professors Van Allen and Ware, head of the Electrical Engineering Department, embraced the idea of my changing my major and worked with me to make the transition painless.

I was leading the work on the Physics Department’s S-46 satellite as my Ph. D. thesis project when I made the change. That project went forward without pause, and Professors Van Allen and Ware served as my joint thesis advisors. Although the launch failed due to a rocket malfunction, the satellite performed flawlessly, and the work led to receipt of my Ph. D. degree in electrical engineering in August 1960.

Dividing my time between the two departments worked exceptionally well. I have always been pleased that I studied physics first, as it reinforced my inclination to follow the physicist’s basic approach to problem solving.

Much has been written about the distinction between the two fields. One expression of the difference is the somewhat tongue-in-cheek assertion that a physicist builds instruments as a necessary adjunct to pursuing his study of nature, while the engineer studies physics in order to support his love of instrument development. By that measure, I fit best in the latter category.

Throughout my postuniversity years, I have felt that I was somewhat uncomfortably straddling the fence between the two fields. Sometimes I enjoyed the benefits of membership in both “clubs,” but sometimes I felt that I was not a full member of either.