Current Status of NAVSTAR GPS.

The launch of the 24th Block II satellite in
March 1994 completed the GPS constellation. The NAVSTAR system currently
consists of 25 satellites, including one Block I satellite. Initial Operational
Capability (IOC) was formally declared December 8, 1993, in a joint announcement
by the DoD and the Department of Transportation (DoT). The IOC notification
means that the NAVSTAR GPS is capable of sustaining the Standard
Positioning Service (SPS), the 100-meter positioning accuracy available to civilian
users of the system on a continuous, worldwide basis. Unlike IOC for
other DoD systems, IOC for GPS has purely civil connotations.

In 1995, the U.S. Air Force Space Command formally declared tha GPS met the
requirements for Full Operational Capability (FOC),meaning that the constellation
of 24 operational (Block II/IIA) satellites now in orbit has successfully
completed testing for military functionality. While the FOC declaration is significant
to DoD because it defines a system as being able to provide full and
supportable military capability, it does not have any significant impact on civil

An additional 21 satellites called Block IIRs are being developed by Martin
Marietta (formerly General Electric Astro Space division) as replacements for
the current GPS satellites. The Block IIR satellites will provide enhanced
performance over the previous generation of GPS satellites, including the capability
to autonomously navigate (AUTONAV) themselves and generate their
own navigation message data. This means that if the control segment cannot
contact the Block IIR satellites, the AUTONAV capabilities will enable these
satellites to maintain full system accuracy for at least 180 days. The Block IIR
satellites will be available for launch as necessary beginning in late 1996.

A follow-on set of replenishment satellites, known as Block IIFs, is planned to
replace the Block IIR satellites at the end of their useful life. The Air Force intends
to buy 33 Block IIF satellitesto sustain the quality of the GPS signal as a
worldwide utility for the foreseeable future.These satellites will have to meet
even higher levels of performance than previous generations of GPS satellites,
including a longer life cycle of 6.5 to 10 years. The IIF satellite will be launched
on an Evolved Expandable Launch Vehicle (EELV). The Air Force issued a
draft request for proposals (RFP) on June 20, 1995, and plans to award a contract
for the development and procurement of the Block IIF satellites in spring

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