Project Echo

Project Echo was the first passive communications satellite experiment. Each of the two American spacecraft, launched in 1960 and 1964, were metalized balloon satellites acting as passive reflectors of microwave signals. Communication signals were transmitted from one location on Earth and bounced off the surface of the satellite to another Earth location.

The first transmissions using Echo were sent from Goldstone, California, to Crawford Hill in Holmdel, New Jersey, on 12 August 1960. The last Echo satellite deorbited and burned up in the atmosphere on 7 June 1969.

The concept of using orbital satellites to relay communications predated space travel, first being advanced by Arthur C. Clarke in 1945. Experiments using the moon as a passive reflecting way station for messages began as early as 1946. With the launching of Sputnik 1, Earth's first artificial satellite, in 1957, interest quickly developed in orbiting communications satellites.

In July 1958, at a US Air Force sponsored meeting on communications satellites, Bell Telephone Laboratories engineer John R. Pierce put forth a presentation on passive satellite relay, describing how a reflective orbiting body could be used to bounce transmissions from one point on the Earth to another. William H. Pickering, director of Jet Propulsion Laboratory (JPL), also attended the conference and suggested that JPL facilities, specifically a 26 m (85 ft) diameter polar-mounted antenna installed near Goldstone Dry Lake in the Mojave Desert, might be used as a ground facility for experiments with such a satellite.

In October 1958, Pierce, along with fellow Bell engineer Rudolf Kompfner, designed an experiment to observe atmospheric refractive effects using reflective balloon satellites. Believing the experiment would advance research toward transoceanic communications via satellites, the two engineers presented a paper advocating for the launch of balloon satellites to be used as passive communications reflectors to the National Symposium on Extended Range and Space Communication on 6 and 7 October 1958.

That same month, the National Aeronautics and Space Administration (NASA) was formed, and two months later JPL was transferred from the United States Army to the new agency. Project Echo, NASA's first communications satellite project, was officially laid out in a 22 January 1959 meeting with representatives from NASA, JPL, and Bell Telephone Laboratories setting the initial launch for September 1959.

Project Echo was a pathfinder mission with the objective of testing new technologies and preparing for future missions. Spaceflight engineers used Echo to prove new ideas and test limits in aerodynamics, satellite shape and size, construction materials, temperature control and satellite tracking. Echo was designed as an experiment to demonstrate the potential of satellite communications, not to function as a global communications system.

Echo was designed, approved and built with the following objectives: