The Iowa cosmic ray group and Argus

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.