have been calculated through the same Doppler method
17
that was used to detect
the Russian satellite.
Although at that moment Sputnik seemed a deadly threat, in reality it encouraged the scientific progress that laid the foundations of the modern GPS. At that
time, APL scientists had been working with the Navy to find a way that would
allow nuclear submarines to figure out their precise location positioning underwater in order to limit surface navigation time. The Sputnik beep represented a brilliant solution. McClure’s ideas immediately aroused the interest of the US military,
which saw the strategic potential advantage of a space-based network of beacons.
Similar to the aeronautical LORAN, this asset would have allowed military vehicles to locate themselves without the assistance of ground stations.
In the seventies, the newly formed APL Space Department designed and
launched into space on behalf of the Navy a constellation of small satellites,
named Transit, which sent radio signals worldwide and was capable of reaching
nuclear submarines. As early as 1975, the Pentagon opened some frequencies for
civil use on merchant and leisure ships, and so the first commercial navigation
devices began to be distributed by American manufacturers.
The Soviet Union also built its own space-based radio-navigation system, called
Cosmos,
18
and launched into space dozens of supporting satellites. Their existence, however, remained unknown to the general public.
In the early eighties, the Pentagon decided to build the second generation of
radio-navigation satellites, more accurate than the previous system and usable
both for the Navy and for the Air Force. The two were in fact secretly working on
two separate space programs, the Air Force’s 621B
19
and the Naval Research
Laboratory’s Timation,
20
but it soon became clear that a single system was the
least expensive solution for them.
It was decided that atomic clock technology would be used onboard the new
satellites to measure time with a level of precision never achieved before and thus
emit radio signals from space in a perfectly synchronized way.
17
As early as the mid-twentieth century, scientists discovered how to measure distances using
radio. The idea behind it was to measure the time it takes for the signal to travel from a transmitting station to a receiving device and multiply it by the speed of the signal itself, which is
equal to the speed of light. It was difficult to take a completely accurate measurement of time,
and even a single millionth of a second of inaccuracy would result in an error of one thousand
feet in the distance calculation. Therefore, for a precise calculation, the receiving system had to
be capable of detecting the travel time of the signal with an accuracy equal to one billionth of
a second.
18
Harvey, Brian. 2001. Russia in Space, the Final Frontier? Cham: Springer-Verlag Publishing,
130.
19
Bray, Hyawatha. 2014. You Are Here: From the Compass to GPS. Basic Books Publishing.
20
https://www.nrl.navy.mil/ssdd/heritage/nts.
GPS: The Stellar Clock 57
17
that was used to detect
the Russian satellite.
Although at that moment Sputnik seemed a deadly threat, in reality it encouraged the scientific progress that laid the foundations of the modern GPS. At that
time, APL scientists had been working with the Navy to find a way that would
allow nuclear submarines to figure out their precise location positioning underwater in order to limit surface navigation time. The Sputnik beep represented a brilliant solution. McClure’s ideas immediately aroused the interest of the US military,
which saw the strategic potential advantage of a space-based network of beacons.
Similar to the aeronautical LORAN, this asset would have allowed military vehicles to locate themselves without the assistance of ground stations.
In the seventies, the newly formed APL Space Department designed and
launched into space on behalf of the Navy a constellation of small satellites,
named Transit, which sent radio signals worldwide and was capable of reaching
nuclear submarines. As early as 1975, the Pentagon opened some frequencies for
civil use on merchant and leisure ships, and so the first commercial navigation
devices began to be distributed by American manufacturers.
The Soviet Union also built its own space-based radio-navigation system, called
Cosmos,
18
and launched into space dozens of supporting satellites. Their existence, however, remained unknown to the general public.
In the early eighties, the Pentagon decided to build the second generation of
radio-navigation satellites, more accurate than the previous system and usable
both for the Navy and for the Air Force. The two were in fact secretly working on
two separate space programs, the Air Force’s 621B
19
and the Naval Research
Laboratory’s Timation,
20
but it soon became clear that a single system was the
least expensive solution for them.
It was decided that atomic clock technology would be used onboard the new
satellites to measure time with a level of precision never achieved before and thus
emit radio signals from space in a perfectly synchronized way.
17
As early as the mid-twentieth century, scientists discovered how to measure distances using
radio. The idea behind it was to measure the time it takes for the signal to travel from a transmitting station to a receiving device and multiply it by the speed of the signal itself, which is
equal to the speed of light. It was difficult to take a completely accurate measurement of time,
and even a single millionth of a second of inaccuracy would result in an error of one thousand
feet in the distance calculation. Therefore, for a precise calculation, the receiving system had to
be capable of detecting the travel time of the signal with an accuracy equal to one billionth of
a second.
18
Harvey, Brian. 2001. Russia in Space, the Final Frontier? Cham: Springer-Verlag Publishing,
130.
19
Bray, Hyawatha. 2014. You Are Here: From the Compass to GPS. Basic Books Publishing.
20
https://www.nrl.navy.mil/ssdd/heritage/nts.
GPS: The Stellar Clock 57