Melbourne, FloridaAugust 1960

On the night of August 18, 1960, a witness in Melbourne, Florida watched the Echo I satellite pass overhead under a clear sky with a bright Milky Way visible. The observer suddenly noticed what he described as an uneasy shadow moving in the exact same position as the satellite. This shadow appeared to blot out stars in the Milky Way as it traveled across the sky, crossing roughly from south-southwest to north-northeast in what the witness estimated took about one minute.

The witness initially wondered if the shadow was cast by the Echo satellite itself. But he quickly changed his mind when he realized the sun was too far to the west to create such a shadow ahead of the satellite. This observation raised three questions in his mind: whether other people had reported the same incident, whether Echo had actually cast a shadow that night, and what object could move so fast if it was not a satellite.

The Air Force's technical intelligence center responded with a detailed explanation. They confirmed that Echo I did indeed cast a shadow, but explained that the shadow was far too small and distant to ever be visible on Earth's surface. The satellite subtends (takes up) such a tiny angle in the sky that observers without optical aid are actually seeing reflected sunlight, similar to how a mirror too small to see at a distance becomes visible only because it reflects light. The center also noted that when an observer can see light reflected off an object like the satellite, the geometry of the situation makes it impossible for that object's shadow to fall on the observer.

The Air Force concluded that with limited data available, they could not determine the cause with certainty. However, they suggested the most probable explanation was a physiological effect: the result of observing intently, holding the head in an unusual position, and experiencing excitement during the observation. The file notes this is not uncommon under such circumstances.

The full case file is reproduced below as held by the National Archives, spanning 17 pages.