Four experimental satellites developed by the Massachusetts Institute of TechnologyLincoln Laboratory were launched during 1965. Built to test advanced communications devices and techniques, three of the four satellites are working satisfactorily even though only one was injected into its planned orbit. The first all solid-state transponders were used to generate rf power at X band. Two antenna pointing systems using inputs from sensors operating at "visible" wavelengths have worked properly within the limitations of incorrect orbits. Voice and data were transmitted through the satellites successfully. Magnetic torquing of the spin axes was used to align the satellites normal to the sun line.UR active experimental satellites developed at Lincoln Laboratory-the first in a program to test techniques for future communications satellites-were launched during 1965. The satellites were used to communicate between the laboratory's ground terminals.New techniques useful in communications satellites included the following: generating X-band rf power in a small, all solid-state transponder; a switched high-gain antenna pointing system at X-band frequencies; highly sophisticated logic to drive the antenna switch; earth and sun sensors operating at "visible" wavelengths to provide inputs to the switching logic; a magnetic torquing system to align the satellite spin axis for thermal control; a follow-on magnetic torquing system to align the satellite spin axis normal to the orbit plane; and the use of micropower logic in a space radiation environment.Early in the development of the first satellite-Lincoln Experimental Satellite, LES-1-it became clear that technique development should be oriented toward a satellite operating in a circular, synchronous, equatorial orbit. As the LES program progressed, devices and techniques tested on one satellite were continuously improved and put aboard succeeding satellites.
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