Reading and tabulating the information

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

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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.