Lincoln Experimental Satellite

Lincoln Experimental Satellite refers to a series of satellites designed and built by Lincoln Laboratory at MIT between 1965 and 1976, under USAF sponsorship, for testing devices and techniques for satellite communication.

The series had satellites named LES1 through LES9. They suffered a number of launch problems - LES1 and LES2 were supposed to be delivered to the same 2800 x 15000km orbit [cite web | url = http://www.astronautix.com/craft/les.htm | title = Astronautix.com] , though a failure of a boost stage left LES1 in a 2800km circular orbit. LES3 and LES4 were intended to be delivered to geostationary orbit, but a launch problem left them in their transfer orbit. All these satellites returned useful results despite the incorrect orbits. LES 5, 6, 8 and 9 ended up successfully in geostationary orbit; the project that would have been LES-7 ran out of funding and was cancelled. cite web | url = http://www.hq.nasa.gov/pao/History/SP-4217/ch8.htm | title = NASA document] .

LES3 was a very small (16kg) satellite containing a radio transmitter, intended to measure the extent of multi-path interference due to reflection of 300MHz radio waves off sufficiently flat parts of the Earth.

Amongst the technologies tested on LES1 through LES4 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. [cite journal | title=The Lincoln Experimental Satellite Program (LES-1,2,3,4): A Progress Report | journal=Proceedings of Communications Satellite Systems Conference May 2-4 1966 | publisher=American Institute of Aeronautics and Astronautics] .

LES8 and LES9 were satellites of around 450kg mass, equipped with pulsed plasma engines; unusually for communication satellites, they are powered by RTGs rather than by solar panels. [cite web | url = http://www.aero.org/publications/martin/martin-8a.html | title = Aerospace Corporation article] There was a cross-link between them in the 36-38GHz part of the K-band, with UHF up- and down-links; they are still operated, and the cross-link technology is used by NASA's TDRSS satellites. The original intention was to run the cross-link at a frequency in the 55-65GHz 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.

Lincoln Laboratory's next satellite-communication project after LES was the construction of FLTSAT EHF Packages.

References

* [http://www.hq.nasa.gov/pao/History/SP-4217/ch8.htm] is a detailed description of satellite communications development at Lincoln Laboratory, and was used as a reference for much of this article.