Project 10073 Record Card and Related Correspondence — Yaak, Montana, September 1952

This document contains a comprehensive collection of reports, statements, and technical data regarding a UAP sighting on September 1, 1952, near Yaak, Montana. Three airmen from the 680th Aircraft Control and Warning Squadron—A/1C Earl C. Ramsey, A/1C Leonard H. Oberdorf, and A/2C Donald E. Williams—reported observing multiple colored lights in the sky. The witnesses described the objects as round, smaller than stars, and capable of erratic maneuvers, including rapid diving and changing colors from green and blue to a yellowish-white. The objects were observed both visually and via an AN/FPS-3 search radar. The radar operators noted that the targets appeared as small, permanent echoes that would remain on the scope for a short time, disappear, and then reappear nearby. The squadron commander, Captain Matthew Sproul Jr., forwarded these statements to higher headquarters, noting that there was no other air traffic within 100 miles of the objects. The documentation includes detailed weather data, including pseudo-adiabatic diagrams, to support an investigation into the atmospheric conditions at the time. Following the investigation, Captain R. L. James concluded that the radar targets were likely ground objects detected due to a mild temperature inversion in the atmosphere. The file also includes a separate, unrelated report regarding a sighting of nine silver objects over Tucson, Arizona, on September 2, 1952, which was investigated by S/A Robert C. Shoemaker.