Early hints of the high-intensity radiation

The earlier rockoon expeditions actually provided a first hint of high-intensity trapped radiation, as described earlier. A few days after Explorer I was launched, we re­ceived another, more substantive indication. The scientists at the Jet Propulsion Laboratory (JPL), primarily Conway Snyder and Phyllis Buwalda, were carefully checking the quality of the initial data. As quickly as possible, they gathered the verbal comments from the station operators and took a look at the data tapes as they arrived to determine the condition of the orbiting instruments and to mea­sure the satellite internal temperatures. In the process, they observed on 5 February that the Geiger-Muller (GM) counter rates appeared at a few times to be zero. Conway immediately notified Bill Pickering, who in turn called Van Allen, start­ing the conversation along the lines, “I have bad news for you. Conway Snyder has looked at the data, and there are no counts. Your instrument appears to have failed.”

Van Allen told me recently that he was noncommittal during that conversation. He had considerable confidence in our instrument and was greatly concerned that premature interpretations of the data might be problematic.13

His reservations and concerns must have been apparent to Pickering, because when I returned to Pasadena the next day, a memorandum lay on my desk that had been issued by Deal’s project director, Jack Froehlich. That terse memo emphatically

CHAPTER 12 • DISCOVERY OF THE TRAPPED RADIATION 325

reinforced the earlier-stated data release policy. It declared, “The two experiments on Deal I, the cosmic ray experiment and the micrometeorite experiment, are the responsibility of the State University of Iowa and the [Air Force Cambridge Research Center] respectively. No member of this Laboratory is authorized to comment on any result of these experiments. Please bear this in mind in all conversations either public or private.”14

We now know that the zero apparent counting rate from that pass was a direct ob­servation of the Earth’s zone of intense radiation. We did not arrive at that conclusion, though, until much more work had been completed with the data from Explorers I and III.