86 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1961 



The research and analysis division has made valuable contributions 

 to our basic knowledge of the earth and the upper atmosphere, 

 described in detail under Space Science. In summary, the division has 

 achieved greater accuracy in the analysis of the earth's gravitational 

 potential field, established the gravitational ellipticity around the 

 earth's equator, and determined the geodetic positions of the observing 

 stations with greater exactness. The division has measured variations 

 of atmospheric density in relation to solar activity and interplanetary 

 storms, and studied the effect of solar light pressure on satellites. 



Dr. Karoly Lassovszky is continuing his astrometric study of satel- 

 lite positions determined from Baker-Nmm films. From approxi- 

 mately 800 measurements on 34 images of different length he 

 analyzed the frequency distribution of settings, the relationship 

 between this distribution and the length of the image, and the rela- 

 tionship between the "magnitude error" and the length of image. 

 Position determinations have been made using reference stars at dif- 

 ferent distances. On the basis of these results, we can conclude that 

 the accuracy is influenced neither by the distortion of the emulsion 

 nor by the optical distortion within an area of a diameter of 5 cm. 

 (5?8). The standard error of a position determined from numerous 

 measurements made with Mann comparators on Baker-Nunn films 

 is ±1?1, both in right ascension and in declination. The project 

 should help evaluate the techniques of analysis and measurement 

 now used for the precise reduction of satellite data. Dr. Lassovszky 

 will also investigate the rapid and secular variations in brightness 

 of satellites. 



At the Florence meeting of COSPAK, April 10-14, 1961, the Di- 

 rector and Dr. George Veis presented a paper on the Observatory's 

 "Experience in Precision Optical Tracking of Satellites for Geodesy." 

 The Baker-Nunn cameras can photograph satellites to an accuracy of 

 about d=2" (seconds of arc) in topocentric position and ±1 milli- 

 second in time. The locations of the cameras have been connected, 

 with standard geodetic techniques, to the major geodetic systems and 

 to a tentative uniform one. From an analysis of the observations, 

 geodetic information of dynamic character has been obtained; i.e., 

 the coefficients of the second, third, fourth, and fifth order zonal 

 harmonics of the earth's gravity field as well as the coefficients of the 

 second order sectorial harmonic. The launching of a well-planned and 

 controlled flashing-light geodetic satellite for international use would 

 reduce markedly the complexity and expense of observing stations 

 and promote international geodesy in a remarkable fashion. 



Space science. — Imre G. Izsak, in the first attempt to derive two 

 important geophysical constants from the motion of satellites, has 

 made a good estimate of the ellipticity of the earth's equator. He has 

 also obtained a second-order solution of Vinti's dynamical problem. 



