observation posts the electromagnetic pulse generated by the explosions. One system used a short base line of approximately 30 miles, and the other a long base Hne*of approximately 1500 miles. Vertically transmitted electromagnetic pulses from 1 to 25 Mc were used to determine the effect of atomic explosions on the height and integrity of the F-layer of the ionosphere. The principal effort in the thermal program was devoted to the measurement of basic thermal characteristics from stations located on or near the ground. A basic ground station placed close to GZ employed calorimeters and radiometers exposed from an instrument tree above ground, with recording instruments being protected underground. Stations farther removed from GZ contained spectrometers, bolometers, radiometers and calorimeters mounted inside instrument trailers. Some of the parameters determined from the basic thermal measurements were irradiance, total radiant energy, and times to first maximum, minimum, and second maximum. The spectrom- eters recorded the spectral distribution of radiant energy with distance. A spectrometer station was mounted in a P2V-2 type aircraft to correlate results of surface and airborne transmission and spectrum measurements. _ ; Alpha-cellulose paper, wood, and other materials were exposed to thermal _ radiation in order to determine critical ignition energies. Various types of. aircraft sandwich panels were exposed to determine the damageeffects of the long thermal pulse associated with high-yield devices. . A technical photography program was conducted to determine photo- grammetrically the various parameters of nuclear clouds as a function of time and to establish appropriate scaling relations. 1.4 SANDIA CORPORATION 1.4.1 Program 30, Vulnerability This program was designed to procure data leading to better knowledge of weapon vulnerability in relation to both blast and close-in thermal damage from the fireball. . The technical objectives of Program 30 were largely realized, although some data were lost owing to electromagnetic transients on Project 30.2. Results of Project 30.1 were extremely encouraging from the standpoint of performance of instrumentation systems within the fireball. -~ 25 - AFWLIHO . Z3