148 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1963 



being prepared for the Orbiting Astronomical Observatories is ex- 

 pected to yield new data not obtainable from ground obsei^vatories. 

 The use of electronic computers of great capacity and capability has 

 allowed consideration of detailed aspects of stellar theories. 



A strong feature of the broad scope of the Observatory's scientific 

 program is the ease with which a scientist investigating some particu- 

 lar topic may draw on information and techniques generated by others 

 pursuing different topics. Particularly gratifying were several cases 

 in which instrumentation developed for a specific project was adapted 

 to a quite different application. The many instances of cross-fertiliza- 

 tion of scientific disciplines occurring within the Observatory's activ- 

 ities make subdivision of its program difficult. This, however, is a 

 small price to pay for the program's increased scientific value. 



Planetary sciences. — With the advent of intensive national and inter- 

 national space programs, interest in the planets has increased remark- 

 ably in both scientific and lay circles. Scientists, including those at 

 the Observatory, have been attracted by the research opportunities 

 offered by scientific spacecraft. 



Studies of the earth were the first to benefit from artificial satellites 

 as a research tool. Scientists at SAO have been leaders in the utiliza- 

 tion of satellite data for many such investigations. 



Three major areas of investigation are based on the precise satellite- 

 tracking data obtained by the network of Baker-Nunn cameras.^ The 

 first is the determination of the density of the earth's atmosphere 

 as a function of position and time. These dependencies, in turn, 

 are used in detailed analyses of atmospheric phenomena and their 

 correlations with other geophysical and solar phenomena. The second 

 important area of investigation is directed initially toward the detailed 

 specification of the earth's gi'avitational potential. This specifica- 

 tion of the geopotential is of basic importance in studies of the interior 

 of the earth. The third area is the determination of accurate geo- 

 metrical positions of the Baker-Nunn stations relative to one another. 

 Kjnowledge of these positions contributes strongly to an improved 

 geometrical figure of the earth. 



Although these three areas of investigation have quite different 

 scientific objectives, they are nevertheless intimately related. Each 

 depends on identification and isolation of factors that influence the 

 accuracy with which a theoretical orbit may be made to fit the obser- 

 vational data. Basically, the analytical process consists of finding 

 the values of such parameters as atmospheric density, geopotential 

 coefficients, and station coordinates, which optimize the agreement 

 between theoretical and observed satellite positions. The effects of 

 these factors are interrelated in such a way that scientific progress 



See footnotes on p. 164, 



