Lincoln Experimental Satellite

In particular, Lincoln aimed to increase the transmission capability of communications satellites ("downlink"), which was necessarily constrained by their limited size.

After receiving a charter in 1963 to build and demonstrate military space communications, Lincoln focused on a number of engineering solutions to the downlink problem including improved antennas, better stabilization of satellites in orbit (which would benefit both downlink and "uplink"—communications from the ground), high-efficiency systems of transmission modulation/de-modulation, and cutting-edge error-checking techniques.

Amongst the technologies tested on LES-1 through LES-4 were solid-state X-band radio equipment, low-power logic circuits, electronic despinning (using optics to determine the location of the Earth and Sun relative to a spinning satellite at any moment, and then transmitting via whichever of several antennae were best positioned with respect to the Earth), and magnetic torquers.

[10] They were originally planned to be equipped with pulsed plasma engines but actually launched with gas thrusters; unusually for communication satellites, they are powered by MHW-RTGs rather than by solar panels.

[12] The original intention was to run the cross-link at a frequency in the 55–65 GHz range, which is absorbed by water, so that it would be impossible for Earth-based receivers to pick up scattered signals, but technology at the time was inadequate.