Leslie H. Meredith

Leslie (Les) H. Meredith was born on 23 October 1927 and lived during most of his childhood in Iowa City. He received most of his college degrees from the University of Iowa: his B. A. in 1950, his M. A. in 1952, and his Ph. D. in 1954, all in physics. His timing was fortunate, as he became Van Allen’s first graduate student.

During parts of 1953 and 1954, Les went to Princeton University to work with Van Allen on the Matterhorn nuclear fusion project.6 Upon receiving his Ph. D. in 1954, he began his postgraduate career at the Naval Research Laboratory (NRL) in Washington, D. C., serving

CHAPTER 1 • SETTING THE STAGE AT THE UNIVERSITY OF IOWA 9

as head of the Rocket Sonde Branch and Meteor and Aurora Section. After the National Aeronautics and Space Administration was signed into law in October 1958, Les became one of the cadre of scientists transferred from the NRL to form what became the Goddard Space Flight Center in Greenbelt, Maryland. Serving for 12 years as chief of its Space Science Division, he provided outstanding leadership in the buildup of Goddard’s research staff and program. By mid-1970 he took over as deputy director of the Space and Earth Sciences Directorate, and after October 1972, he served for nearly three years as Goddard’s assistant director.

During subsequent years, Les moved through a progression of upper-level management positions, culminating in a short tour as the Goddard Center’s acting director. After his retirement as a federal government employee, he worked for nine years with the 13-agency U. S. Global Change Research Program.

In 2003, he and his wife, Marilyn, moved to their retirement home at North Myrtle Beach in North Carolina. Marilyn died in 2008, but Les has continued to reside there.

Les’ early balloons were launched from a football practice field on the east bank of the Iowa River from 16 June 1951 (beginning only five months after Van Allen’s arrival) through 26 January 1952. His scientific objective was to measure the incoming cosmic ray intensity as a function of altitude with a directional telescope using thin-walled Geiger-Muller (GM) counters. A concomitant purpose was to help the department gain initial experience with counters and coincidence circuits, telemetering techniques, and balloon flying.

That first Iowa balloon apparatus employed an array of three in-line, thin-walled, cylindrical, Victoreen-type 1B85 GM counters, with a coincidence circuit to form a directional telescope. An event from the center counter was counted, but only when the top and bottom counters were triggered at essentially the same time. Thus, only particles traveling vertically through all three counters were registered. The output of that telescope, along with an altitude measurement, was sent to ground by a frequency-modulated (FM/FM) telemetering system adapted from a design originally developed by Thomas Coor at Princeton University.7 Height-measuring barometers and transmitters taken from surplus weather radiosondes were included. Meredith’s circuits employed 13 miniature acorn vacuum tubes, each measuring about one-half inch in diameter and one and one-half inches in length.

His apparatus, with batteries, was assembled in a frame constructed of one-half inch, lightweight angle stock riveted together to form a boxlike structure measuring 15 by 15 by 30 inches. The gondola was completely covered with celluloid and partly covered with white paper to control the temperature of the instrument during its several-hour flight.

A number of inexpensive Darex type-J weather balloons of about six foot diameter were used to loft the instruments. Multiple small balloons were used rather than a single larger one. Not only were the smaller ones less expensive, but their use also freed the flights from the tight constraints of the Federal Aviation Administration— the larger balloons would have presented a potential hazard to aviation, whereas the smaller ones would not endanger the aircraft. The number of balloons was chosen so

OPENING SPACE RESEARCH

that their net free lift was about twice the total weight of the gondola and its rigging. For a payload weight of 27 pounds, a typical arrangement included nine balloons, each with 6 pounds lift.

Some of Les’ recollections about these earliest developments are entertaining and revealing.8 He stated, “The system test… was to take [the instrument] to the first high hill that you came to on the highway going south along the river, I think it was about five miles out of town, and then turn it on. The signal strength and counter operation were then checked at the receiving station, which was located in the attic of the physics building.” He continued, “Each balloon was of… some kind of rubber that had to be boiled just prior to launch to be flexible.” Recalling the field operation: “At launch, with the balloons at an angle because of any breeze, I and a helper ran with the payload until the balloons were high enough so the gondola wouldn’t swing down and hit the ground.”9

Out of Meredith’s seven flights in that series, the first two, flown on 16 June and 6 July 1951, produced somewhat noisy but usable data. Flight 3 failed to produce any usable data. Flights 4, 5, and 6 were flown with simple test equipment instead of with the more valuable instruments in order to work out some of the remaining technical details. The seventh and last flight in the series, launched 26 January 1952, produced good data throughout most of the flight. Preparation for the launch of the final flight is shown in Figure 1.1.

The three productive flights in this series served as the basis for Meredith’s master’s thesis, in which he established a new value for cosmic ray vertical intensity at that latitude for particles above an energy threshold that was lower than had previously been measured.10