ASTRONOMY AND ARTIFICIAL SATELLITES—GOLDBERG 289 
Lyot in 1930. The series of spectra show that the ozone layer begins 
to be penetrated at a height of 8 kilometers, that the penetration is 
accelerated at higher altitudes, and that it is complete at 55 kilome- 
ters. Many subsequent flights to heights greater than 200 kilometers 
by the NRL group and by Rense and his collaborators at the Uni- 
versity of Colorado have further lengthened the solar spectrum by 
photography to below 100 A. The emission of X-rays from the sun 
has also been studied, chiefly by Friedman and his associates, also 
at the Naval Research Laboratory, and their observations have been 
an important feature of the program of the IGY. After depletion 
of the supply of German V-2 rockets, the program has been con- 
tinued with Viking and Aerobee rockets of U.S. manufacture, which 
have been launched both from the ground and from balloons in a 
combination called the Rockoon. 
In spite of the very many great achievements which have been ac- 
complished with rockets, the technique suffers from serious limitations, 
the most important of which is the very short space of time—a few 
minutes at the most—during which the rocket is at the top of its 
trajectory and observations are possible. It has been clear for some 
time that these limitations could be removed if it were possible to 
place a large rocket into a stable orbit high above the earth—in other 
words, to transform the rocket into an artificial satellite of the earth. 
In this way, the age-old dream could be realized of a laboratory or 
observatory in space from which the astronomer would have an un- 
obstructed view of the universe. The first indication that this dream 
might become a reality was given by the spectacular advances in 
rocketry in Germany during World War II. As early as 1946, feasi- 
bility studies in this country had demonstrated the practicability of 
artificial satellites with then-existing rocket technology, although the 
cost would have been comparable to that of the Manhattan Project 
for the development of the atomic bomb, However, these studies were 
not known to astronomers generally, and even when, in 1955, both 
the United States and the Soviet Union announced their plans to 
launch artificial satellites as activities of the IGY, the small sizes of 
the satellites that were announced made it appear that the astronomi- 
cal applications would be extremely limited and highly specialized 
for many years to come. 
The news that the Soviet Union had succeeded, on October 4, 1957, 
in launching an earth satellite with an instrument payload of 184 
pounds came as a surprise to most astronomers, who had no knowledge 
that such large payloads were feasible. The first shock of surprise 
was soon compounded when the much heavier second and third sput- 
niks were placed in orbit. 
However, the shock has now worn off and has been replaced by 
eager anticipation of the consequences for astronomy of artificial 
