Tuesday, 11 February 2003: 4:00 PM
What were the scientific implications of Military support for Upper-air Research on Radio Wave Propagation in the 1940's?
In the years from 1941 onwards, first during wartime and then as part of the burgeoning Cold War, the United States sought to develop its capabilities of command, control and integration by extending the reach of its radiocommunication network to encircle the world. Communications over distances so great that the wave had to be guided by the ionosphere were of major importance to both sides during World War II. These difficulties of radio wave propagation, and in predicting the dynamics of the upper atmosphere, made the ionosphere unreliable as a resource to utilise. Commencing immediately after the attack on Pearl Harbor, the US military organised for the construction of a network of research stations to map the ionosphere in an effort to better understand it. Coordinated internationally between the wartime Allies, and centered around the National Bureau of Standards Radio Section and the Division of Terrestrial Magnetism at the Carnegie Institution of Washington, an unprecedented program was launched to analyse ionospheric radiowave propagation and the upper atmosphere across the globe. The aim of this program was to create a comprehensive and systematic set of data from which projections of ionospheric activity could be made, and through which the ionosphere could be rendered more stable and predictable. While the military's needs were transparent, the implications of this program for science were less so. The secret research program and its classified results found their analogy in an opaque set of value changes that underlay the scientific work conducted on the military payroll. This research signified an important change of emphasis and shift in direction for studies of the upper atmosphere. Since no sampling was possible above balloon altitude, from 1924 onwards research had focused on the use of radio sounding techniques. Teams headed by Edward Appleton and J.A. Ratcliffe, Merle Tuve and Gregory Briet, and E.O. Hulburt at the Naval Research Laboratory collected data on the electron content of the upper atmosphere by studying radio wave echoes that were reflected back from a vertical transmission. As a result, prior to 1940 significant gains had been made in upper atmosphere research, particularly in the appreciation of the nature of the medium at altitudes above the troposphere. The trajectory of these researches, although earthbound observations using remote sensory equipment, followed a model of classical scientific study. Even relying on remote interaction with the phenomena under study the key questions concerned the state of the atmosphere, its chemistry and physics, its consistency and composition. While the question of properties remained central, driven by the exigencies of Military requirements and their need for tools, this new research initiative was driven rather by considerations of behaviour.