The space navigation onboard system “Alpha” that had been developed in the years 1966-1968 by the Institute of Applied Mathematics of USSR Academy of Sciences and by the Central Design Office for Experimental Engineering Industry of the Ministry for the Common Engineering Industry for the Project L-1 of the manned fly-by the Moon is described in the Presentation. To obtain the onboard measuring information, there was used a sextant that allowed receiving by the cosmonauts the optical measurements of the angular elevations of the known stars above the horizons of the Earth and the Moon. There are presented the principal properties of the ballistic algorithm of the navigation that was giving the possibility to the SC crew to determine the SC orbit and to correct it for all the parts of the flight to ensure the SC safe entrance into the Earth atmosphere. The problems that were connected with the realization of the algorithm at the onboard computer, which existed that time, are shown. The system of autonomous navigation was successfully tested by the development engineers and cosmonauts for fly-bys the Moon with the automatic version of the spacecraft (the SC “Zond 5- Zond 8”) from 1968 till 1970. These tests showed that this onboard navigation system “Alpha” satisfied to all the time and accuracy conditions in the orbit and correction determination. These characteristics of the system “Alpha” were practically not worse than ones for the ground navigation system.

Theoretical and applied problems of mechanics