Zero racks were provided for each surface and underwater experiment. A total of 32 racks were used. On four experiments, TU-5 installed and operated a recording system to monitor temperature and humidity at the zero point. At the Parry and Enyu control points, TU-5 employed a new world time clesie-accurate to 2 0.1 msec and a series of Bhangmeters to record preliminary yield information. These pieces of equipment were triggered by light from the explosion. At each control point a weather radar system was employed to assure good line of sight to the diagnostic stations. The timing and firing systems successfully detonated 32 surface and underwater shots. The Bikini system was used on 10 UCRL shots. The Eniwetok systems were used to detonate 15 Los Alamos Scientific Laboratory experiments, 2 DOD underwater events, and 5 UCRL experiments. The Boxer system synchronized timing with the Sandia system. The Johnston system synchronized experimental signal requirements with the ABMA missile system. World time was recorded on 29 surface shots. Light to minimum records, which gave an early approximation of yield, were obtained on 27 surface shots. Approximately 4200 signals were transmitted. The timing system functioned properly on all events. Two postponements were experienced on Bikini Atoll due to signal cable failures. A ship's power failure on event Wahoo caused loss of some experimental data. Technical Photography. TU-5 performed technical photography of the visible aspects of all detonations as a service to the Los Alamos Scientific Laboratory, the Livermore laboratory, and the Department of Defense. The major tasks on Laboratory events were to photograph fireball growth for determination of yield and to record cloud growth and motion. DOD projects entailed much more detailed photography of specific underwater and high altitude phenomena. For the Laboratory shots, camera stations were located on Bikini and Eniwetok Atolls. A total of 10 stations were activated. At least two stations were used on each detonation to provide accurate determination of fireball growth and cloud formation. To maintain dual capability, the major stations were outfitted to cover at least two zero sites. This was attained by providing two independent systems of cameras at each of six locations. For AEC requirements Eastman High Speed, Mitchell High Speed, Triad, Fastax, and Rapatronic cameras were used. Photographic commitments for the DOD necessitated the outfitting of 23 separate stations. and in aircraft. These stations were on land, lagoon barges, shipboard, All photo stations were completely automatic, being initiated by hardwire or radio signals and controlled discrete timers. Film recoveries were made as soon as possible after each event and processed in the trailer fa- cilities on Parry Island. Approximately 150,000 ft of photographic film was exposed in the course of Hardtack. Preliminary analysis was performed in the Forward Area on all fireball records. Reports on fireball yield calculations were issued in the field on all but the last shot, Fig. Alpha Measurements, On Hardtack TU-5 was scheduled to perform reaction history measurements on all Los Alamos Scientific Laboratory ex- periments. These measurements included alpha va time throughout the required portion of measurable history, boost measurements, and peak level 123