SECRETARY'S REPORT 87 



In his study of satellite orbits with very small eccentricities he has 

 found that the orbit has two perigees and two apogees during each 

 revolution. He is continuing his investigation of the harmonics of 

 the earth's gravitational potential. 



Dr. Don A. Lautman has undertaken a numerical integration pro- 

 gram to provide precise ephemerides of artificial satellites. He will 

 check general perturbation theories and attempt to obtain orbits of 

 satellites not at present subject to general theory, as well as of those 

 whose perturbations are too large or too complicated to be handled 

 conveniently by general perturbation theories. 



Dr. Yoshihide Kozai has shown that the effects of solar-radiation 

 pressure must be considered in the derivation of geodetic constants 

 from satellite data. He is continuing his studies of astronomical con- 

 stants and of the geodetic uses of artifical satellites. By analysis of 

 deviations of computed orbits from those observed by Baker-Nunn 

 cameras, he is attempting to determine the tesseral harmonics of the 

 earth's gravitational potential and to obtain accurate coordinates of 

 the camera stations. He will employ recently determined values from 

 the motion of satellites to examine the relations between astronomical 

 constants and to eliminate inconsistencies. Dr. Kozai's determina- 

 tions from satellites of the spherical harmonics to the fifth order of the 

 earth's gravitational field are generally accepted as the most precise 

 available. 



Pedro E. Zadunaisky, from a preliminary study of atmospheric 

 drag on nonspherical satellites, has attempted to find a "mean" attitude 

 of satellites in relation to their velocity vectors. He will continue with 

 more refined techniques and a different group of satellites at higher 

 altitudes. His analysis will contribute to our knowledge of 

 atmospheric densities and of the motion of satellites around their 

 center of gravity. His special study of the perturbations on the orbit 

 of Echo I caused by atmospheric drag and solar-radiation pressure 

 gave good agreement between theory and observation. 



Dr. Gustav A. Bakos is progressing with his analysis of the seasonal 

 changes of the earth's albedo. The project has significance for our 

 understanding of the relationship which he has demonstrated between 

 large-scale meteorological phenomena and the observed reflectivity of 

 the earth. 



Stephen E. Strom has developed the computer program and 

 preliminary ray-tracing method for the study of the effect of the 

 ionosphere on radio-astronomical observations. 



Dr. Mario D. Grossi, with these computations and tracings as tools, 

 will investigate the effect of the ionosphere, the Van Allen belts, and 

 the earth's magnetic field on radio-astronomical observations in the 

 MF and HF bands. 



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