Echo 1 and car

This image, with the car in the foreground, gives a better sense of the scale of the Echo balloon, which was 100 feet in diameter. The Mylar surface of the balloon reflected signals from Earth, making it a passive communications satellite--or "satelloon," as it was sometimes known at NASA. It handled radio, television, and telephone signals, including the first coast-to-coast phone call via satellite.

The Mylar polyester film was just 0.5 mil (0.0127 mm) thick. With its highly reflective surface, the Echo 1 was said to be easy to spot from the ground with the naked eye.