speak at length about Sputnik. Understandable pride was evident in Blagonravov's bearing, but his words also bristled with barbs for his American listeners. The speaker could not—or at any rate did not-refrain from chiding the United States for talking so much about its satellite before having one in orbit, and commended to his listeners the Soviet approach of doing something first and then talking about it.

While there was some measure of justice in Blagonravov's ungracious comments, his U.S. colleagues couldn't help feeling that he missed-perhaps intentionally-the point that much of the advance discussion of the U.S. IGY satellite program was to provide necessary information for planning by those who wished to cooperate in the tracking or other operational aspects of the mission. In view of the fruitlessness of CSAGI's efforts to elicit any such accommodation from the Soviets, either at Barcelona in 1956 or at the meetings in Washington, the remarks of their Russian colleague were doubly frustrating.14

Nevertheless, admiration for the Soviet achievement was genuine and universal, and his colleagues could heartily applaud when Blagonravov declared that he hoped that "this first step" would "serve as an inspiration to scientists throughout the world to accelerate their efforts to explore and solve the mysteries and phenomena of nature remaining to be explored."'15

Reaction in the United States was strong and widespread. It was clear, albeit intuitively to most, that a new dimension had been added to man's sphere of thought and action. Equally clearly, something had to be done about the fact that the United States had not been the first to put a satellite in orbit. One read and heard talk about Soviet technological supremacy, U.S. loss of leadership, the missile gap, and security and economic implications. In view of the impressively large weights of Sputnik 1 (80 kg) and 2 (508 kg, 3 Nov. 1957), and the multiton launch vehicles that they implied, the 82-kg payload of Explorer 1 launched on 31 January 1958 did little to allay such concerns. President Eisenhower attempted to downplay the Soviet achievement, but couldn't carry it off. 16 Congress took the matter seriously, largely through apprehension over military implications, and began to crank up the machinery to respond to what was viewed as a crisis. On his part, Eisenhower created the post of science adviser to the president, elevated his Science Advisory Committee to White House level, and asked the committee to develop a national policy on space. The result was to be the National Aeronautics and Space Act of 1958.

By now atmospheric and space science had moved far beyond the narrow confines of the Rocket and Satellite Research Panel and had established a base from which the space science program could proceed following the creation of the National Aeronautics and Space Administration in the summer and fall of 1958. From the membership of its technical panels on rocketry and on the earth satellite program, the academy established a Space Science Board in June 1958, to advise the government in what prom

ised to be a fast-growing and important field. Lloyd Berkner was named chairman of SSB (app. F).

Events of the next three-quarters of a year after the first Sputnik launching make a fascinating and educational story as Congress and the administration cooperated and wrestled with each other to hammer out a legislative response to the crisis.17 A number of circumstances combined to give scientists the civilian agency and open space program they favored. How this came about will be dealt with in chapter 7. But before proceeding to that part of the narrative, it is appropriate to pause and take stock of the rich harvest of scientific knowledge that a decade of rocket sounding had already produced before artificial earth satellites took on an importance that commanded the attention of the president and the Congress.

6

Early Harvest:

The Upper Atmosphere and Cosmic Rays

Scheduling V-2 flights, developing newer rockets, testing instruments, seeking financial support, fighting military classification, arguing and politicking in meetings national and international—such activities seemed to consume more time and energy than the actual science that was their ultimate purpose. But because of those subsidiary activities, which fill most of the pages of this book, the scientific research moved steadily forward. Month by month, year by year the results accumulated. By the time NASA began to operate, a rich harvest had already been reaped from sounding rockets, with several significant contributions from the scientific satellite program of the International Geophysical Year. These, especially upper atmospheric and cosmic ray research, gave NASA a running start in space science.

By the early 1960s the study of energetic particles and magnetic fields from the sun and their interaction with the earth's magnetic field had become a well integrated and coherent field of study. By then, also, satellite geodesy had begun to make its mark. But the space science program was open ended, and the harvest a continuing one. This steady advance of space science is the subject of three chapters (6, 11, 20), whose aim is to present in broad outline what the space science disciplines encompassed and to show how space techniques made notable contributions. The present chapter reviews achievements through 1958.

THE THRESHOLD TO SPACE

Thirty thousand light-years from the center of a disk-shaped galaxy, itself measuring 100000 light-years from edge to edge, planet Earth revolves endlessly around an average star, the sun, which with its attendant planets speeds toward remote Vega, brightest star in the northern skies. Although containing billions of stars, nebulas, and other celestial objects, most of the galaxy consists of empty, or nearly empty, space. To inhabitants of Earth the threshold to these outer voids is the upper atmosphere.

One can easily show theoretically that the pressure and density of the atmosphere must decrease exponentially with increasing height above the ground, and experiment confirms this conclusion.1 Roughly, at least for the first hundred kilometers, pressure and density fall to one-tenth their former value for every 10-mile (16-km) increase in altitude. Hence, above 30 km only one percent of the atmosphere remains, while beyond 100 km lies only one-millionth of the atmosphere.

Interest in the lower atmosphere where people live and experience the continuous round of changes in weather and climate is obvious, but one might well ask what could possibly hold the attention, even of scientists, in a region so nearly empty as the upper atmosphere? The initial impression, however, is misleading. After closer study the upper atmosphere is found to exhibit many fascinating, often practically important phenomena—such as the ionosphere, which profoundly influences radio communications, especially shortwave; the auroras; electric currents, which at times cause magnetic effects that blank out both radio and telephone links; and the ozonosphere, which during the debate over fluorocarbon-propelled aerosols gained temporary stature in the public mind as the protecting layer that shields the earth's surface from life-killing ultraviolet rays of the sun. So interesting were the challenging phenomena of the upper atmosphere that by the time sounding rockets put in their appearance, scientists had already evolved from afar a coherent, comprehensive picture of the upper atmosphere and solar-terrestrial relationships. In the mid-1940s this remarkably complete picture formed a paradigm that hundreds of geophysicists around the world shared and used in reporting their continuing researches at scientific meetings and in the literature.

The main features of this paradigm were set forth in an article on the upper atmosphere by B. Haurwitz, first published in 1936 and 1937 and reissued with some updating in 1941.2 For those who began using sounding rockets in 1946 to explore the upper atmosphere, Haurwitz's concise review provided a helpful introduction, while a review paper by T. H. Johnson told much of what was known about cosmic rays from groundbased and balloon researches.3 A classic paper by Fred Whipple on the use of meteor observations to deduce atmospheric densities at altitudes between 50 and 110 km was one of the best examples of the ingenuity necessary in studying a region not yet accessible to them or their instruments.1 But the work that best described the state of knowledge of the earth's high atmosphere at the very time when the sounding rocket program was getting under way in the United States was a book of more than 600 pages, The Upper Atmosphere, by Indian scientist S. K. Mitra. Mitra furnished an exhaustive review of upper-atmospheric research, concluding with a chapter summarizing what had been learned and listing some of the most important problems needing further research. The very last paragraph noted that as the volume was going to press word had reached him:

that experiments are being conducted in the U.S.A. with the V-2 rockets to study the cosmic rays and the ionospheric conductivity up to heights of 150 km (August, 1946). It is hoped that the scope of these experiments will be extended and that the records obtained therefrom will, on the one hand, give direct information of upper atmospheric conditions and on the other reveal the true picture of the intensity distribution of solar ultraviolet radiation and thus help to solve the many mysteries of the upper atmosphere which till now have resisted all attacks.5

Mitra's hopes paralleled the motivations of the sounding rocket experimenters, many of whom were entering what was to them an entirely new field.

Following is an elaboration of the extensive paradigm that the space scientists inherited from the ground-based researchers (fig. 1). The description is based on the works cited above, especially on Mitra's treatise.

The atmosphere extended to great heights, auroras being observed on occasion to more than 1000 km. Pressure and density were calculated and observed to fall off in exponential fashion. If the temperature were uniform throughout the atmosphere, the decline in these quantities would be given by

and

p = po exp(-h/H)

P = Po exp(-h/H)

(1)

(2)

where p and p denoted pressure and density respectively, the subscript zero indicated values at the ground, and h was altitude. The quantity H, known as the scale height, was given by

where

H = kT/Mg

k

=

Boltzmann constant = 1.372 × 10-16 erg/degree

T = temperature in kelvins

M = mean molecular mass of the air = 4.8 × 10-23 gm

(3)

In (1) and (2) the value of g was assumed to be constant, whereas in actuality gravity varies inversely as the square of the distance from the