oan fw PrIN SERIE « wm DETECTION OF FIREBALL LICHT AT DISTANCES OBJECTIVES This project was performed in order to obtain further ii. :rmation on the feasibisity cf detecting the light emitted at the time of a nuclear detonation at ‘stances of 1,600 km or more. It was hoped to use this phenomena to further the usefulnezs of the Long Range Detection System. More specific objectives can be summarized aa‘lows: (1) Gain additional information on the mechanism of light transmission along the curvature of the earth; (2) determine energy released by measurement of curves of light intenstiy versus PER TL Ipreteens 72 I ER ge eR SIRERN Metoe RO ORS Ee time; (3) determine attenuation factors at a ground station and an aircraft station, both the same distance from the bomb detonation point; and (4) obtain operaticaal experience under field conditions for possibie future use. BACKGROUND . Visual sightings of the light from an atomic explosion at distances of several hundred miles were reported during Sandstone (Operation Fitzwilliam), Spring 1948, and Ranger, early 1961. AFOAT-1 has supported meamirements to determine the characteristics of the emitted light at various distances during Greenhouse (Reference 1)(early summer 1951); Baster (Reference 2) (fall 1951); and Snapper (Reference 3) (early summvr 1952). A detection of Greenhouse Easy at the Pacific Proving Ground was made from a plane 12,500 feet above the surface of the ocean at a distance of 1,000 km from the detonation point. The calculated yield by measurement of time to minimum light gave 700d cgree~ ment with thet obtained in the vicinity of the detonation. Attempte to mecoure the light from the earth's surface at Saipan (1,850 km) on the occasion of Shot Dog, and Wake (380 km) on the occasion of Shots Dog and Easy, were unsuccessful. No aitempts were made to perform long range light detection experiments during Shot George because the detonation took place in daylight, when detection was impossible with the equipraent then in use. Sinoe it was understood that Shot :tem would also be detonsted after sunup, the personnel and equipment were returned to the United States before detonation time. Experiments during Buster at the Nevada Proving Ground utilized both a alit camera at Las Vegas, approximately 110 lan from the detonation point, and photoelectric equipment insensitive to constant or slowly varying light, at Flagstaff, Arizona (430 km) and Albuquerque, New Mexico (885 km). Equipment difficulties at Las Vegas resulted in only one successful detection (Shot Easy). At Flagstaff, at least one channel furnished a positive record for all shots attempted (Baker, Charlie, Deg, Easy}. No detections were made at Albuquerque, due mostly to stormy weather at the chose. mountain site. Wherever a cetection could be made, there was genorally good agreement between the time to fee mee pe ee ee ee eee ee er