This is from the NGS CORS Newsletter….

20th Anniversary of Initial Operational Capability of the GPS Constellation

GPS Directorate Press Release

14 January 2014


The Global Positioning System (GPS) Directorate celebrated the 20th Anniversary

of achieving Initial Operational Capability (IOC) for GPS Dec. 8, 2013.


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 century.


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 IOC.


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.