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Astronomy From Artificial Satellites 
By Leo GOLDBERG 
Director, The Observatory of the University of Michigan 
Ann Arbor, Mich. 
[With 4 plates] 
THE ELIMINATION of the earth’s atmosphere as a barrier to observa- 
tion has been dreamed of by generations of astronomers who have at- 
tempted to survey the universe from the bottom of a dirty and turbu- 
lent ocean of air. Considerable improvement is effected when 
observatories are placed on high mountain tops, far above fogs and 
low-lying clouds. At heights of 1 to 2 miles above sea level, where 
such observatories are located, the air is very pure, but no matter how 
pure, it is still air and therefore subversive of the goals of astronomy. 
It is only by placing telescopes completely above the earth’s atmos- 
phere that the astronomer can obtain a clear and unobstructed view 
of the heavens. It now seems certain that such an extraterrestrial 
observatory will soon be an accomplished fact, thanks to the achieve- 
ment of artificial satellites, the most exciting advance in observing 
technique since the invention of the telescope. 
There are three major reasons why the atmosphere is a hindrance 
to astronomical research. First, even the very tiny amount that is 
present above a height of several miles is completely opaque to all 
ultraviolet radiation of wavelength shorter than about 2,900 A., and 
to much of the infrared radiation of longer wavelength. Second, the 
air is never completely steady even above high mountains. Local 
fluctuations in temperature induce violent currents of boiling air 
which distort the images of celestial bodies. The turbulence of the air 
has been responsible for the sharp difference of opinion concerning 
the nature of small details on the surface of the sun and for 
heated arguments as to the reality of the canals on Mars. Third, the 
atoms and molecules in the atmosphere scatter sunlight by day, and 
also emit radiation, which is visible by night. The bright daylight 
sky obliterates the faint light from the solar corona, and the airglow 
at night masks the radiation from the background of faint stars and 
1The 25th annual James Arthur lecture on the sun, given under the auspices of the 
Smithsonian Institution, Oct. 23, 1958. 
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