Report on the Astrophysical Observatory 



Sm: I have the honor to submit the following report on the 

 operations of the Smithsonian Astrophysical Observatory for the fis- 

 cal year ended Jmie 30, 1961 : 



The Astrophysical Observatory includes two divisions: the Divi- 

 sion of Astrophysical Research in Cambridge, for the study of solar 

 and other types of energy impinging on the earth; and the Division 

 of Radiation and Organisms in Washington, for the investigation of 

 radiation as it relates directly or indirectly to biological problems. 

 Shops are maintained in Washington for work in metals, woods, and 

 optical electronics, and to prepare special equipment for both divi- 

 sions; and a shop conducted in cooperation with the Harvard Col- 

 lege Observatory in Cambridge provides high-precision mechanical 

 work. The field station at Table Mountain, Calif., carries out solar 

 observations. Twelve satellite-tracking stations are in operation, 

 in Florida, Hawaii, and New Mexico in the United States and abroad 

 in Argentina, Australia, Curagao, India, Iran, Japan, Peru, South 

 Africa, and Spain. 



DIVISION OF ASTROPHYSICAL RESEARCH 



The Observatory research staff made significant contributions to 

 knowledge of solar astrophysics, meteors, meteorites, artificial satel- 

 lites, geophysics, and space science. The continuing refinement of 

 observational tecliniques and the development of new analytical 

 methods provided valuable data and opened up new areas of astro- 

 physical investigation. 



The Observatory continued, with mutual benefit, its close liaison 

 with Harvard College Observatory, the Massachusetts Institute of 

 Technology, Boston University, and other research centers. 



Solar astrophysics. — Dr. Paul W. Hodge studied the properties of 

 the field stars and globular clusters in the Large Magellanic Cloud 

 and found that they apparently differ from our galaxy in color, mag- 

 nitudes, luminosity, and evolutionary pattern. These findings are 

 important in establishing the true extragalactic distance scale. 



Stephen E. Strom completed his study of absorption below 100 A. 

 to determine the optical depth of the interstellar medium as a func- 

 tion of wavelength in the X-ray region. He found that the region 

 above 40 A. is essentially "black" (in terms of presently conceived 

 fluxes) and that, owing to the K-absorption limit of oxygen, there is 



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