Project 10073 Record Card and Air Intelligence Information Report — 30 July 1951

This document consists of a Project 10073 record card and an Air Intelligence Information Report regarding an unconventional unidentified object observed on 30 July 1951. The object was detected by radar operators at the 752nd AC&W Squadron in Empire, Michigan, between 1114Z and 1132Z. The radar return, described as an oblong blip with a conventional tail, exhibited extreme speed variations, ranging from an estimated 3,000 to 28,000 miles per hour. The report notes that high scatter clouds were present in the vicinity, but observatories at the University of Michigan and Yerkes Observatory reported no unusual meteoric activity. The official evaluation by technical representatives at the 30th Air Division (Defense) concluded that the phenomenon was likely caused by anomalous propagation resulting from electronic interference between the Empire radar station and a radar transmitter located at Elkhorn, Wisconsin. The report details that the two radar sets were operating on the same frequency with similar pulse repetition frequencies and antenna rotation rates, which created the observed scope presentation. The author, 1st Lt. Robert K. Hall, noted that the extreme speeds recorded would have been physically impossible for a flying device due to atmospheric friction and heat. The document includes distribution lists for the Air Materiel Command and Air Defense Command, and is marked for downgrading at three-year intervals.