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20th Anniversary of Initial Operational Capability of the GPS Constellation

LOS ANGELES AIR FORCE BASE, El Segundo, Calif. -- The Global Positioning System (GPS) Directorate celebrated the 20th
Anniversary of achieving Initial Operational Capability (IOC) for GPS Dec. 8

In 1973, the Navstar Global Positioning System Joint Program Office
(JPO), headed by then-Colonel Bradford Parkinson, developed the GPS
architecture and initiated efforts to field a prototype system to prove the
concept of space-based global navigation would work. Since that time, GPS
has evolved from an idea, to a prototype, to a global utility. It continues
to evolve, with modernization bringing forth new capabilities for the 21st

Since the launch of the prototype Block 0 satellite June 22, 1977,
GPS has provided high quality navigation signals to suitably equipped users
across the globe. Beginning in 1978, after the first four developmental
Block-I satellites were launched, GPS started to provide full 4-dimensional
positioning, navigation, and timing (PNT) services to military and civilian
users on a limited, but worldwide, basis. By 1985, the seven remaining
developmental Block I satellites were launched to expand the availability of
PNT services around both time and space. The second stage of GPS began Feb.
14, 1989 when the first operational Block II satellite was launched into
orbit. More Block II and Block IIA launches followed rapidly thereafter
until, Dec 8, 1993, United States Air Force Space Command (AFSPC) declared
IOC for GPS when a grand total of 24 Block I and Block II/IIA satellites
were operating in their individual orbits and providing the Standard
Positioning Service (SPS) to civilian users and the Precise Positioning
Service (PPS) to authorized military users.

After IOC, additional Block IIA satellites were launched to fully
populate the baseline operational constellation of 24 slots arranged in six
orbital planes --the remaining developmental Block I satellites continued
providing high quality navigation signals even though they were not part of
the baseline operational constellation. Once system testing was complete,
AFSPC declared Full Operational Capability (FOC) for the GPS constellation
April 27, 1995, signifying the system met all requirements with 24
operational Block II/IIA satellites in their assigned orbital slots and
providing both the military PPS and the civil SPS.

Today, the GPS constellation remains healthy, stable and robust with
31 operational satellites on-orbit broadcasting the PNT services 24 hours a
day, 7 days a week, 365 days a year. In the 20 years since IOC, GPS has
never failed to deliver on the global PNT service commitments made by the
Department of Defense in the PPS Performance Standard (PPS PS) and in the
SPS Performance Standard (SPS PS) - both of which trace directly back to the
original Global Positioning System (GPS) Standard Positioning Service Signal
Specification (SPS SS) which was officially promulgated on Dec. 8, 1993 by
the Assistant Secretary of Defense for Command, Control, Communication and
Intelligence (C3I) as the formal document which defined IOC. Amazingly,
though many Navstar satellites have been launched and been decommissioned
over the past 20 years, four of the original Block IIA satellites which made
up the IOC constellation (SVN-23, SVN-26, SVN-34, and SVN-39) are still
operating and providing reliable PNT services as of this 20th Anniversary of

GPS has grown to become a vital worldwide utility serving billions
of users around the globe. GPS multi-use PNT services are integral to the
United States global security, economy, and transportation safety, and are a
critical part of our national infrastructure. GPS contributes vital
capabilities to our nation's military operations, emergency response,
agriculture, aviation, maritime, roads and highways, surveying and mapping,
and telecommunications industries, as well as recreational activities. It
is not an overstatement to say GPS is fundamental to today's technical
infrastructure and culture. GPS provides the 'winning edge' to our
warfighters and allies by delivering premier space-based PNT services to the
nation and the world.