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Less celebrated than Cheyenne Mountain, its Colorado Springs Cold
War cousin, Schriever Air Force Base’s role may be even
more significant in the enveloping electronic world. Among a host
of space warfare and satellite functions at the base, Schriever
is the control center for the global positioning system, the only
system of its kind in the world, and a system that is increasingly
vital to military and civilian infrastructure. GPS operates using
the speed of light rate of electronic signals to determine the
relative distance between objects. To do so it couples the most
precise clocks in the world to a global network of satellites
whose position is precisely monitored and measured.
For the centuries before the space age, military superiority
was largely determined at sea. The invention of longitude as a
ship-based navigation system, using accurate portable clocks on
board ships and calculating distances relative to known celestial
entities, revolutionized the ability for colonial scouts and imperial
forces to discover, conquer, and control the world. The center
for this global navigational system was Greenwich, England, at
the seat of the ruling empire of the era. Global time, and global
space (longitude) was calibrated from this point, and governed
by the Royal Navy.
Due to this historic and critical foundation for timekeeping,
the Navy has traditionally controlled time in the United States
as well, based out of the Naval Observatory in Washington DC (which
shares its grounds with the official Vice President’s residence).
The nation’s “Master Clock,” regulated by the
atomic decay of hydrogen, resides at the observatory, overseen
by the Director of Time Service, and the Superintendent of the
Naval Observatory, who is designated as the DOD Precise Time and
Time Interval (PTTI) Manager.
In the past few decades however, the global systems of surveillance,
communication, and navigation have steadily moved upwards, above
the roiling seas, into space, borne by satellites. And in the
USA, space is not the Navy’s realm, it is the Air Force’s.
With the development of GPS, the Air Force finally captured some
control of Time from the Navy, and now has an official atomic
clock of its own, the “Alternate Master Clock.” While
the calibration of the Alternate Master Clock is linked to the
Navy’s Master Clock in Washington,* and its existence is
often explained as being a redundant back-up of the Master Clock,
it is, as official Coast Guard documents explain, “capable
of independent performance” suggesting some degree of autonomy
for the Air Force. And, it is located at Schriever, confirming
its status as the Greenwich of the Space Age.
Since nearly all military bases in the USA have origins in or
soon after WWII, Schriever, established from scratch as Falcon
Air Force Station in 1983 (renamed Schriever in 1998), is quite
possibly the newest major military base in the country. It was
built on 3,800 acres in the rolling plains, several miles east
of its parent, Petersen Air Force Base. Its original stated function
was to be a back up satellite control facility for Onizuka Air
Force Station, in Mountain View, California, where all DOD satellites
were being controlled from at that time (from the famous “Blue
Cube” building, visible next the highway, and surrounded
by Lockheed’s main satellite manufacturing plant). By 1987,
Schriever had control of most of the DODs satellites, including
the Navstar System, the original Global Positioning Satellite
network.
At all times there are at least 24 operational satellites in
the GPS constellation (sometimes as many as 29), guaranteeing
that at least three or four satellites are visible simultaneously
from any place on earth. To control this continuously orbiting
network, monitoring locations positioned around the globe (in
Guam, Ascension Island, Diego Garcia, Hawaii, California, Colorado,
Florida, Greenland, and the UK) send information to Schreiver’s
Master Control Center. In addition to keeping track of the location
of these satellites to a degree of precision measured in nanoseconds,
some of these monitoring stations also upload adjusted time and
location information from Schriever to the satellites. Additionally,
each satellite has its own atomic clock, and all onboard clocks
are centrally calibrated by the Alternate Master Clock at Schriever.
This global network of monitoring locations and earthstations,
controlled by the Master Control Station at Schriever, operates
instantaneously and continuously, and connects to all the satellites
in the GPS constellation. As a result, each satellite knows exactly
where it is at any given moment, and beams this information back
to earth as a continuous stream of radio waves. These radio waves
are picked up by GPS receivers the world over, whether they are
on aircraft carriers, or in the hands of hikers with Garmins from
Walmart. With a minimum of three separate satellite location/time
streams, the GPS device does a little math to triangulate its
own location relative to those “fixed” points in space.
As the receiver moves, its position relative to those points is
continuously recalculated, and a three dimensional picture of
its position, heading, speed and altitude is formed, another object
moving through space. It is all relative to, and centered in,
the time/space hub of Colorado Springs, Colorado.
* The “calibration” of time, and a global agreement
of what time it really is, is determined by machines and complex
diplomatic international agreements and policies involving several
different time types and standards of deviation (Coordinated Universal
Time, International Atomic Time, etc.) Thousands of people the
world over must be involved in “global time” vocations
– an international temporal bureaucracy. The machines involved
are generally what are called “atomic clocks,” as
they use some form of atomic oscillation to regulate them. Both
of the US’s Master Clocks, at the Naval Observatory and
at Schriever, use devices known as hydrogen masers, caster-mounted
file-cabinet sized appliances manufactured by the Symmetricom
company in Beverly, Massachusetts. |
