Lincoln Experimental Satellite turns 40
by Barbra Gottschalk | Communications and Community Outreach Office
In March 2016, the Laboratory recognized a Milsatcom milestone. March 14th marked the 40th anniversary of the last launch of the LES satellites. LES-9, the final satellite, is still operational today and is believed to be the longest continuously operating communications satellite in U.S. history.
The Lincoln Experimental Satellite (LES) program, one of the Laboratory’s earliest pioneering inventions, was a monumental technical achievement that created the foundation for Milsatcom today. In a celebratory event, key staff members described the ground breaking achievements of the LES-9, its long-term impacts, and how it is still being used today.
Launched in 1976, LES-9 is a three-axis stabilized satellite built by the Laboratory and powered by a radioisotope thermoelectric generator. A technological feat of its time, the satellite supported two-way communications with small mobile user terminals at 75 bps, as well as vocoded voice conferencing and data exchanges at up to 19,200 bps among larger mobile command post terminals.
The satellite was built to demonstrate high reliability, survivability, and strategic communications technologies. It was designed to operate in coplanar, inclined, circular, geosynchronous orbits and to communicate via crosslinks at extremely high frequency, and with terminals operating on or near the surface of the earth at both extremely high frequency and ultrahigh frequency. A multi-service test program verified and documented that the actual on-orbit performance was consistent with the underlying performance theory. Extensive pre-launch testing was conducted because of the complex transmission and reception for satellite links providing antijam capability.
The experimental communications satellite was developed for the U.S. Air Force and included ground breaking features such as a processed payload, crosslinks, autonomous operation, and communication at millimeter wave frequencies. David McElroy, Principal Staff in the Communications Division, recalled the insights gained from work on the satellite, "LES-9 demonstrated critical technologies that set the stage for current military secure antijam military satellite communications systems."
Over 40 years of operation, LES-9 supported a variety of military and scientific missions including providing polar coverage for Coast Guard and NSF personnel. Today, LES-9 continues to provide low-power UHF communication. Still in orbit, LES-8 and 9 have no solar cells (which are vulnerable to radiation damage) or batteries and are instead powered by radioisotope thermoelectric generators that provide continuous electrical power. Signal-processing circuits on the satellites are designed to resist jamming and interference and to provide simultaneous multiple access. In addition, the satellite also contains the standard systems and subsystems that deal with attitude control, on-board propulsion, and telemetry.
The Director of the Laboratory, Eric Evans, indicated "This anniversary event illustrates the Laboratory’s decades-long commitment to reliable space communications" and he thanked the more than 50 alumni of the program that were able to attend the celebration for their contributions to the LES program.
Posted March 2016
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