Participation of Bell Telephone Laboratories in Project Echo and Experimental Results

On August 12, 1960, a 100-foot-diameter spherical balloon was placed in orbit around the earth by the National Aeronautics and Space Administration. The objective was to demonstrate the feasibility of long distance communication by means of reflection of microwaves from a satellite. It was intended that a two-way coast-to-coast voice circuit be established between the Jet Propulsion Laboratories facility at Goldstone, California, and a station provided for this purpose by Bell Telephone Laboratories at Holmdel, New Jersey. Similar tests were also planned with the Naval Research Laboratory and other stations. Construction of the Holmdel station was begun early in 1959. This paper describes the general organization and operation of the station, and discusses the results of the Project Echo experiments that took place between the launching of the balloon March 1, 1961. Successful voice communication wvas achieved a number of times using a variety oj modulation methods, including frequency modulation with feedback, amplitude modulation, single-sideband modulation, and narrow-band phase modulation. Careful measurements were also made of the loss in the transmission path.