86 AJSTNUAL REPORT SMITHSONIAN INSTITUTION, 1960 



the Aircraft Armaments Corporation, Cockeysvillo, Md. Prelimi- 

 nary experiments are expected to be launched in an Aerobee-hi rocket 

 early in 1961, and the satellite should orbit in 19G2. 



This project is of prune importance for the study of stellar and 

 interstellar radiation m the far ultraviolet and soft X-ray regions 

 of the spectrum. It should provide spectrograms, and television pic- 

 tures, at three wavelengths, of the entire celestial sphere. 



Meteoritical studies. — To stimulate interest in essential earth-based 

 meteoritical research, the Director has outlined the most important 

 meteoritical investigations to be carried out m the United States dur- 

 ing the next few years, and has evaluated their importance, m a re- 

 port to the National Academy of Sciences. As President of Sub- 

 commission 22 of the International Astronomical Union, he is 

 preparing a report on world-wide meteoritical research. 



The Director and Dr. Jacchia completed an analysis of the orbits 

 of 413 meteors photographed simultaneously by two stations with the 

 Super-Schmidt meteor cameras to determine the physical nature of 

 meteors and the distribution of their orbits in space. This work 

 represents the largest amomit of precise data yet obtained on meteor 

 orbits and is vital to an understanding of the origin of meteors, their 

 possible interaction with space vehicles, and the nature of comets and 

 the zodiacal light. Analysis indicates that more than 98 percent of 

 all photographic meteors have a fragile structure, are of cometary 

 origin, and are members of tlie solar system. There is no evidence 

 for an interstellar source for meteors. 



In a further analysis of this large amount of photographic mate- 

 rial, Dr. Jacchia is studying individual meteors to improve the theory 

 of meteors and to obtain more information on meteor i)henomena 

 such as the fragmentation process and coma formation. 



Continuing his study of comets, the Director is carrying out theo- 

 retical work on the structure of the cometary nucleus, and has nearly 

 completed calculations relating to the distribution of lifetimes of 

 long-period comets. He has derived a law for the frequency distri- 

 bution of cometary lifetimes. This work contributes significantly 

 to our understanding of the nature and evolution of comets and 

 meteors. 



Dr. E. L. Fireman, Dr. Hodge, Dr. Frances W. Wright, Dr. G. 

 Kistner, Hai Chin Rhee, and Kenneth Covey continued the analysis 

 of stratospheric dust collected at high altitudes by aircraft, balloons, 

 and rockets, to determine the nature and quantity of interplanetary 

 matter accreted by the earth. Preliminary results indicate that at 

 heights above 50,000 feet the amount of terrestrial dust is greater 

 than had been supposed, and that the influx of meteoritic particles 

 into the earth's atmosphere is smaller than had been expected. Mi- 



