Syncom (for "synchronous communication satellite") started as a 1961 NASA program for active geosynchronous communication satellites, all of which were developed and manufactured by Hughes Space and Communications. Syncom 2, launched in 1963, was the world's first geosynchronous communications satellite.

Syncom
Syncom
Syncom and its successors
Syncom: World’s First Geostationary Satellite
SYNCOM-Plus – An Optimized Residue Treatment Process
Even Tesseral Harmonics in the Geopotential Derived from Syncom 2
Attitude determination and control of SYNCOM, Early Bird, and applications technology satellites.
Attitude determination and control of the Syncom, Early Bird, and applications technology satellites
Variation in ionospheric electron content measured by radio waves from Syncom 3
A determination of Earth equatorial ellipticity from seven months of Syncom 2 longitude drift