By Dr Roger D Launius
National Air and Space Museum, Smithsonian Institution
It came like a shock to the system nearly 50 years ago on 4 October, 1957. The Soviet Union launched a beach ball-sized orbital satellite to usher in the "space age".
The act in itself proved neither particularly shocking nor threatening but what it signalled certainly was: the sense that if the Soviets could put an orbital spacecraft over our heads it could bring a nuclear missile down on our heads.
This resulted in a total reorientation of priorities in the United States and the establishment of the National Aeronautics and Space Administration (Nasa) as a focal point for space activities.
At the same time, a little-known principle critical to the safety of the entire world also resulted from Sputnik.
The Soviet satellite established the overwhelmingly critical principle of overflight in space.
The world was safer as a result, but it might have turned out another way
This is the ability to send reconnaissance and other satellites over a foreign nation for any non-lethal purpose free from the fear of attack on them.
Orbiting reconnaissance satellites served more than virtually any other technology as a stabilising influence in the Cold War.
Eyes in the sky
The ability to see what rivals were doing helped to ensure that national leaders on both sides did not make decisions based on faulty intelligence.
Both the Americans and the Soviets benefited from this capability, and the world was safer as a result, but it might have turned out another way.
In a critical document, Meeting the Threat of Surprise Attack, issued on 14 February 1955, US defence officials raised the question of international law governing territorial waters and airspace, in which individual nations controlled those regions as if they were their own soil.
Did President Eisenhower hold back US efforts to launch a satellite?
That international custom allowed nations to board and confiscate vessels within territorial waters near their coastlines and to force down aircraft flying in their territorial airspace.
This has resulted in shoot-downs on occasion, as when the Soviet Union downed a Korean Air Lines Boeing 747 in 1983.
But in 1957 space as a territory had not yet been defined, and US leaders argued that it should be recognised as beyond the normal confines of territorial limits.
An opposite position, however, argued for the extension of territorial limits into space above a nation into infinity.
Access all areas
"Freedom of space" became an extremely significant issue for those concerned with orbiting satellites, because the imposition of territorial prerogatives outside the atmosphere could legally restrict any nation from orbiting satellites without the permission of nations that might be overflown.
Since the US was in a position to capitalise on this freedom of space, it favoured an open position.
Many other nations had little interest in establishing a free access policy that allowed the US to orbit reconnaissance satellites overhead.
By launching Sputnik, the Soviets "did the US a good turn"
US President Dwight D Eisenhower tried to obtain a freedom of space decision on 21 July, 1955, when he proposed it at a US/USSR summit in Geneva, Switzerland.
Soviet Premier Nikita Khrushchev rejected the proposal, however, saying that it was an obvious American attempt to "accumulate target information". Eisenhower later admitted: "We knew the Soviets wouldn't accept it, but we took a look and thought it was a good move." The Americans thereafter worked quietly to establish the precedent.
Then Sputnik, a scientific satellite, overflew the United States and other nations of the world. On 8 October, 1957, an Eisenhower advisor, Donald Quarles, offered this irony to the US president: "The Russians have... done us a good turn, unintentionally, in establishing the concept of freedom of international space."
Seizing the moment
Eisenhower immediately grasped this as the precedent for overflight and pressed ahead with the launching of a reconnaissance satellite, and eventually first did so in 1960.
The precedent held for later satellites and by the end of 1958 the tenuous principle of freedom of space had been established.
By allowing the Soviet Union to lead in this area, the Russian space programme had established the US-backed precedent for free overflight.
America eventually launched its own satellite in 1958.
Throughout 1958 the Eisenhower administration affirmed the free-access-to-space position already established in precedent and declared that space would not be used for warlike purposes.
At the same time it asserted that reconnaissance satellites and other military support activities that could be aided by satellites, such as communications and weather, were peaceful activities since they assisted in strategic deterrence and therefore averted war.
This was a critical space policy decision as it provided for open use of space and fashioned a virtual "inspection system" to forewarn of surprise attack through the use of reconnaissance satellites.
Conspiracy to lose?
Some have speculated that Eisenhower might actually have held back the US effort to launch an orbital satellite to allow the Soviets to do so first, thereby establishing this all-important principle of overflight.
After all, had the US launched before the Soviet Union, Khrushchev might have protested it as a violation of his nation's airspace.
This could have thrown the freedom of space concept into years of intense and confrontational international negotiation.
While this is a fascinating possibility, there is no evidence to believe that the Eisenhower administration actually conspired to lose the race to launch the first satellite.
Instead, establishing the precedent of freedom of space is much more likely a mere serendipity from the Soviet Sputnik launch.
It was an important serendipity, without question; and as is so often the case in history the unintended consequences of actions turn out to be more important than the intended ones.
The story of the establishment of freedom of space is a critical case of an unintended consequence of momentous importance for the rest of the Cold War.
Dr Roger D Launius is chair of the Division of Space History at the National Air and Space Museum in Washington DC and is a former chief historian at Nasa.