SECRETARY'S REPORT 89 



Space science. — Dr. Whitney made a detailed theoretical study of 

 the tumbling of Explorer IV by numerical integration of the gravi- 

 tional forces on the satellite. He also carried out theoretical studies 

 of the thermal balance and nighttime cooling of the ionosphere. 



Dr. Yoshihide Kozai investigated the effects of solar radiation on 

 the motion of earth satellites, and derived general mathematical ex- 

 pressions for the variations of orbital elements of a close earth satel- 

 lite moving under the gravitational field of the earth. He has derived 

 nmnerical values for the amplitudes of the second, third, fourth, and 

 fifth harmonics of the earth's gravity field and has begun work to 

 derive the coefficients of the tesseral harmonics. 



Dr. Don A. Lautman completed work on the determination of the 

 orbit of Satellite 1958 Epsilon during the lifetime of its telemetry 

 and during its entire lifetime; the orbit is more precise by an order 

 of magnitude than previous orbits. He has also found the effects on 

 the orbit of the third harmonic in the earth's potential. 



Imre G. Izsak is developing a method of orbit determination from 

 simultaneous Doppler-shift measurements from three photographic 

 tracking stations. With this method good orbits can be determined 

 from a single passage, regardless of the weather. From Baker-Numi 

 and radio data, he determined definitive elements for an 80-day period 

 in the lifetime of Satellite 1958 Gamma (Explorer III). By appli- 

 cation of Jacobi's elliptic functions, ]Mi\ Izsak seeks to obtain a solu- 

 tion to Vinti's dynamical problem, which is closely related to the 

 perturbations caused by the earth's flattening. 



Rajendra C. Nigam has studied the orbits of Satellites 1959 al and 

 a2. He has also completed a reanalysis of the orbit of Satellite 1958 

 Zeta ; this work has particular value because of the short lifetime and 

 low elevation of the satellite. 



Dr. Pedro E. Zadunaisky began an analysis to determine the orienta- 

 tion of satellites by comparing the drag perturbations on nonspherical 

 satellites with those on spherical satellites. This work will amplify 

 our knowledge of atmospheric densities and the motion of a satellite 

 around its center of gravity. 



The measurement of the earth's albedo and a study of its possible 

 correlation with meteorological phenomena have continued under the 

 supervision of Dr. Gustav A. Bakos. An analysis of results obtained 

 in 1958 has begun. 



The Communications Center, under the supervision of Charles M. 

 Peterson, continues to clear an average of 500,000 words per month. 

 About 90 percent of the messages sent and received contained satellite 

 observations, predictions, and orbital elements. 



579421— Gl 8 



