SECRETARY'S REPORT 79 



A/m ratios to moon-aroimd-earth orbits. Related research includes 

 the effect of lunar orbital eccentricities on moon satellites with large 

 semimajor axis, and the problem of the asteroidal belt and the law of 

 distribution of apsidal lines. Results should contribute to informa- 

 tion about dust particles emanating from the moon, orbits of moon 

 satellites, and space navigation and communication. 



G. H. Conant, Jr., began an analysis of techniques of numerical 

 integration of orbits to determine the nature of error "buildup" as a 

 function of time, and possibly to devise new methods for minimizing 

 this factor. The program has special pertinence to satellite and lunar- 

 probe research. 



Dr. Mario D. Grossi studied the effect of the ionosphere, the Van 

 Allen belts, and the earth's magnetic field on radio-astronomical ob- 

 servations in IMF and HF bands. Using the Hamiltonian ray-tracing 

 for his analysis, he has written a program for computation on IBM- 

 7090. He has demonstrated the existence of a continuous series of 

 focal regions produced by the earth's ionosphere and has applied his 

 results with some success to the problem of Jovian decameter radio 

 bursts. 



Imre G. Izsak, seeking increased accuracy of geodetic data derived 

 from satellite observations, devised a modification of differential orbit 

 improvement using residuals of observations along the orbit and in 

 the normal direction to it with different, empirically determined 

 weights. He constructed a precise theory of the critical inclination 

 for more adequate knowledge of satellite motion. He also developed 

 a computer program to make satellite orbits with very small eccentri- 

 cities useful for the determination of odd zonal harmonics. Using 

 precisely reduced Baker-Nunn satellite observation, he finds coeffi- 

 cients with 0.5 percent standard error, which is the highest accuracy 

 achieved yet. For his continuing research into the tesseral harmonics 

 of the geopotential, he is developing a computer program more satis- 

 factory than that provided by an earlier method. In collaboration 

 with Dr. Michael P. Bamett of Massachusetts Institute of Technology, 

 he is also working on the application of computers to the analytical 

 development of the planetary disturbing function in the restricted 

 problem of tlu^ee bodies. 



Dr. Luigi G. Jacchia has concluded a significant portion of his study 

 of atmospheric drag on artificial satellites, at present the only reliable 

 source of information on atmospheric densities above 200 km. His 

 analysis confirms the theory of the semiannual effect of interaction 

 between the solar wind and the upper atmosphere, its amplitude 

 varying with the 11-year solar cycle; reveals the influence of geo- 

 magnetic perturbations on the temperature of the upper atmosphere ; 

 provides correlations between atmospheric temperatures and the solar 



