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NAVSTAR Global Positioning System(GPS) Block IIR (U)

Overview (U):

(U) NAVSTAR Global Positioning System (GPS) is a satellite-based radio positioning/navigation (POS/NAV) system that provides extremely accurate, three dimensional, common grid position, velocity and time of day information to users anywhere on or near the earth. The system uses a constellation of 24 satellites which provides navigation data to both military and civilian users worldwide. The system provides reliable and accurate passive worldwide positioning, navigation, and timing information in all weather conditions, in real time, using a common grid reference system.

(U) The BLOCK IIR satellites, SVNs 41 through 62, are the operational replenishment satellites developed by General Electric (now Lockheed Martin) and will carry the GPS well into the next century.

Description (U):

(U) The Space Segment is an earth-orbiting constellation of 24 NAVSTAR satellites in six planes. The nominal circular orbit has a 20,200 kilometer (10,900 nautical mile) altitude and the orbits are inclined at an angle of 55 degrees with a 12-hour period. The spacing of satellites in their orbital planes are arranged such that a minimum of four satellites will be in view everywhere on and near the surface of the earth at any time. Each NAVSTAR satellite is designed to broadcast a pair of L-band radio frequency (RF) signals, known as Link 1 (L1 = 1575.42 MHz) and Link 2 (L2 = 1227.6 MHz). The L1 signal carries a precision ranging code and coarse / acquisition code, while L2 carries only the precise ranging code. The signals are broadcast using spread spectrum techniques, employing two different spreading functions: a 1.023 MHz coarse / acquisition (C/A) code on L1 only and a 10.23 MHz precision (P) code on both L1 and L2. The minimum signal power for the different signals at a GPS receiver are: L1 C/A = -160 dBW; L1 P = -163 dBW; and for L2 P = -166 dBW. Superimposed on these codes are low-rate navigation message data, including satellite clock and ephemeris parameters, satellite signal health data, and Coordinated Universal Time (UTC) synchronization information.

(U) In 1989, the Block IIR procurement began for 21 additional satellites ("replenishment SVs") from Lockheed Martin, formerly General Electric. The Block IIR SVs will present an identical SIS interface to the User Segment. Under a survivability scenario, the Block IIR SVs will have the capabilities to autonomously navigate (AUTONAV) themselves and generate their own 50 Hz navigation message data. These AUTONAV capabilities will enable the Block IIR SVs to maintain full SIS accuracy for at least 180 days without Control Segment support. AUTONAV will also significantly improve both the reliability and integrity of the broadcast SIS. Accuracy improvements are expected to be approximately 7 meters spherical error probable (SEP) in a full Block IIR constellation. Additional differences between IIR and IIA are:

- (U) additional radiation hardening
- (U) cross link ranging
- (U) reprogrammable micro-processor
- (U) two atomic clocks on at all times (hot backup)
- (U) 3 Ni CAD to 2 NiH batteries
- (U) manual acquisition/pointing to autonomous
- (U) larger fuel capacity
- (U) redundancy management system in SV processor

(U) The Block IIR satellites will be launched as needed to replace existing Block IIA satellites in order to sustain a 24 satellite constellation.

(U) The GPS control or ground segment consists of five unmanned monitor stations located around the world (Hawaii; Kwajalein in the Pacific Ocean; Diego Garcia in the Indian Ocean; Ascension Island in the Atlantic Ocean; and Colorado Springs, Colorado); a master ground station at Schriever Air Force Base in Colorado Springs, Colorado; and four large ground antenna stations that broadcast signals to the satellites. The stations also track and monitor the GPS satellites.

User Impact (U):

(U) GPS provides an all-weather, global, protected (encrypted) navigation signal to all DoD users and allies. The signal provides positioning accuracy's to about 7m 50 percentile spherical error probable and a timing signal for DoD communications and command and control systems to a precision of <100ns dual root mean square. GPS receivers vary in capability and performance but are being integrated into many operational systems at costs under $3,000/platform.

Programmatics (U):

(U) Operational/Programmed.

Images (U):

Added Value to the WarfighterAFSPC Vision
Global Positioning System (GPS)Five Principles of Global Positioning
This Table Is Unclassified.

Related Initiatives (U):
3A Airborne Receiver3A Airborne Receiver
3S Shipborne Receiver3S Shipborne Receiver
Arnold Engineer Dev Cntr (AEDC)Arnold Engineering Development Center (AEDC)
Combat Survivor Evader LocatorCombat Survivor Evader Locator (CSEL)
CRPA/AE-1Controlled Reception Pattern Antenna (CRPA/AE-1)
Defense Advanced GPS ReceiverDefense Advanced GPS Receiver (DAGR)
Delta IIDelta II
Eastern RangeEastern Range
Embedded GPS Inertial Nav. Sys.Embedded Global Positioning System (GPS) Inertial (EGI) Navigation System
FRPA./AE-4Fixed Reception Pattern Antenna (FRPA)/Antenna Electronics (AE-4)
GAS-1 CRPA/AEGAS-1Controlled Reception Pattern Antenna (CRPA)/AE
GPS Block IIANAVSTAR Global Positioning System(GPS) Block IIA
GPS Block IIFNAVSTAR Global Positioning System(GPS) Block IIF
GPS Receiver Applications ModuleGlobal Positioning System (GPS) Receiver Applications Module (GRAM)
GPS VME Receiver Card (GVRC)GPS Versa Modula Eurocard (VME) Receiver Card (GVRC)
Miniature Airborne GPS Rec. 2000Miniature Airborne Onboard Processing (GPS) Receiver 2000 (MAGR-2000)
Miniaturized Airborne GPS Rec.Miniaturized Airborne Global Positioning System (GPS) Receiver (MAGR)
Precision Lightweight GPS Rec.Precision Lightweight GPS Receiver (PLGR)
This Table Is Unclassified.

Related Requirements (U):None.

Related Categories (U):
NavigationDoD Space Navigation Programs
Satellite OperationsSatellite Operations
Space SystemsSpace Systems
Space-Based WarningSpace-Based Warning Systems
This Table Is Unclassified.

Road Map Placements (U):

Major DoD Space ProgramsEvolution of the Selected Space Programs
National Security Space Road MapIntegrated System Road Map
This Table Is Unclassified.

Requirements, Funding and Additional Hotlinks (U):

GPS-Army Info
Sattelite Control ORD (95)
This Table Is Unclassified.

Lead Office (U):

(U) Air Force.

(U) DoD: OASD(C3I), Pentagon, Washington, DC
(U) Service Staff: SAF/AQS, Pentagon, Washington, DC
(U) Major Command: HQ AFSPC/DR, Peterson AFB, CO; HQ ACC/DR, Langley AFB, VA
(U) Program Management: SMC/CZ, Los Angeles AFB, CA

Point of Contact (U):

(U) Maj Chuck Kastenholz, SMC, Open Phone: (310) 363-6402.

Date Of Information (U):

(U) 01 November 1997

(U) Road Map Production Date: 12 July 1999

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