Project 10073 Record Card — Napa, California, 15 August 1952

On August 15, 1952, at 1700 PDT, a witness named Diane Robinson observed an unidentified aerial object while stationed at a Ground Observer Corps (GOC) post in Napa, California. The witness reported seeing a single, silver-colored, cigar-shaped object, estimated to be the size of a large aircraft. The object was observed for approximately 30 seconds as it traveled in a straight line toward the southwest at an estimated speed of 800 to 1000 miles per hour at an altitude of 10,000 feet. The witness reported that no sound was emitted by the object. The sighting was reported to the 28th Air Division at Hamilton Air Force Base. Official documentation, including a Project 10073 record card and a teletype message, indicates that the investigation considered the possibility of a balloon. Weather data provided in the report noted that a balloon had been released from Oakland 180 minutes prior to the sighting, and wind conditions at 10,000 feet were recorded as 230 degrees at 9 knots. Based on this information, the final evaluation concluded that the object was 'probably a balloon.' The report includes various administrative forms, including a weather data sheet and a worksheet, confirming the details of the observation and the subsequent analysis by the Air Technical Intelligence Center.