1.4.2.9  Degraded Operation and Aiding

During periods of high levels of jamming, the receiver may not be able to maintain both code and

carrier tracking.  The receiver normally has the capability to maintain code tracking even when

carrier tracking is no longer possible. If only code tracking is available, the receiver will slew the

locally generated carrier and code signals based on predicted rather than measured Doppler shifts.

 These predictions are performed by the receiver processor, which may have additional PVT

information available from an external aiding source.  See Chapter 7 for additional discussion of

GPS receiver aiding.

1.5  PROGRAM MANAGEMENT

1.5.1  System Development and Management

The United States Air Force (USAF), Air Force Materiel Command, Space and Missile Center

(SMC), Navstar GPS Joint Program Office (JPO) has total system responsibility for the GPS. 

The SMC and GPS JPO are located at the Los Angeles Air Force Base (AFB) in Los Angeles,

California.  The GPS JPO is manned by personnel from the USAF, US Navy, US Army, US

Marine Corps, US Department of Transportation, US Defense Mapping Agency.  NATO Nations

and Australia may have representatives stationed at the JPO.  The GPS JPO was responsible for

development of the Control and Space Segments and is responsible for acquisition of

replenishment satellites and common user equipment (UE) for all military services.  The GPS JPO

also provides technical support, security guidance, technical specification development, interface

control documents, and implementation guidelines.  NATO and other allied Nations have

established Memoranda of Understanding with the United States which provides access to PPS,

interchange of technical information, and the ability to purchase or locally manufacture PPS GPS

UE.

The GPS JPO is supported by the Launch Vehicle System Program Office (SPO) and the

Network SPO, also located at the SMC.  The Launch Vehicle SPO provides the expendable

boosters used to launch the Navstar satellites.  The Network SPO is responsible for continuing

development of the multi use AFSCN.  GPS JPO program management operations are also

supported by the User Equipment Support Program Manager located at the Warner Robbins Air

Logistics Center in Warner Robbins, Georgia and by Detachment 25 (from the Sacramento Air

Logistics Center) located at Colorado Springs, Colorado.

1.5.2  System Requirements, Planning, and Operations

The USAF Space Command (AFSPC) is responsible for GPS requirements, planning, and

operations.  Headquarters of the AFSPC and the requirements and planning functions are located

at Peterson AFB in Colorado Springs, Colorado.  Various agencies within the USAF Space

Command (AFSPC) operate and maintain the Control Segment, prepare and launch the Navstar

satellites, manage the operational constellation, and interface with the GPS user community. 

Elements of the AFSPC Fiftieth Space Wing (50SPW) are responsible for launch, early orbit

support, and continued day to day operations of the GPS satellites.

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