4150N 3336W (ATLANTIC), May 1961May 1961

On May 11, 1961, six officers and four crew members aboard a ship in the Atlantic Ocean spotted a white, round object resembling a bright star. The ship was located at coordinates 41 degrees, 50 minutes north and 33 degrees, 36 minutes west, traveling at 8,500 feet altitude on a heading of 255 degrees. The object was first spotted at bearing 248 degrees (roughly west-southwest) at an elevation of about 40 degrees above the horizon. It disappeared twenty minutes later into haze on the horizon at bearing 259 degrees and 15 degrees elevation. The observers used binoculars and a sextant to track the object, but radar did not detect it. Visibility was clear with no clouds overhead and no moonlight.

Military observers described the object as appearing to be a satellite. However, in a separate report filed the same day, an analysis sheet concluded the object was probably a refraction of a bright star, likely Procyon. The analysis noted that a witness had reported a similar colored object on May 10 at roughly the same hour and bearing, suggesting atmospheric refraction of a bright star rather than a genuine unknown object. The file notes that the characteristics observed, including color changes from silver to cherry red, were consistent with how a bright star appears under certain atmospheric conditions.

The U.S. Air Force ultimately determined the sighting was Echo I, a satellite launched in 1960. The full case file of 20 pages is reproduced below as held by the National Archives.