A537, Space Orientation Course

1
Military Use of GPS
2
Overview

• Navigation Mission
• GPS Segments
• FBCB2
• Summary

3
Navigation Mission

• Provide precise position, velocity, and time to
  users
• - Worldwide
• - Any weather
• - 24 Hours/day

4
System Segments
Space Segment
User Segment
Control Segment
5
Space Segment

• Block IIA - 7 1/2 year design life
• Block IIR - 10 year design life
• Launched by Delta II from Cape Canaveral

6
Space Segment

• 24 satellites in constellation
• 6 orbital planes, 4 satellites in each plane
• 55 degree orbit inclination
• Semisynchronous orbit
• 12 hour period
• 12,500 statute miles (10,900 nm) altitude
• Constellation maximizes 3-D coverage
• Ensures at least four satellites are visible to
  user anywhere in the world (usually 6-7 visible)

7
Space Segment(Constellation Phasing)

• The GPS constellation is designed to provide 24
  hour coverage with graceful degradation.

8
Monitor Stations Ground Antennas
Cape Canaveral
Colorado Springs
Kwajalein
Hawaii
Diego Garcia
Ascension Island
5 Ground Antennas Receive/send TTC Update NAV
message and atomic clocks
5 Monitor Stations Collect measurements from GPS
satellites in view
9
The User Segment

• Authorized Users Military personnel, military
  systems, designated allies, and other authorized
  users
• Non-Authorized Users Civilians and commercial
  firms around the world. Civilian and commercial
  users of GPS greatly outnumber those of the
  military, and the system is transitioning to
  allow Non-Authorized users greater accuracy.

10
GPS Services

• Standard Positioning Service (SPS)
• Intended for Non-Authorized Users
• Provides decreased location and timing accuracy
• Horizontal position within 100m or better (95)
• Timing accuracy within 340ns of UTC (95)
• Actual error based on current DoD Policy
• Corrupts navigation signal by two methods
• Epsilon changes the satellites position
• Dither changes the satellites time
• Precise Positioning Service (PPS)
• Intended for Authorized (military) users
• Provides very precise location and time accuracy
• 3-D position within 16m Spherical Error
  Probability (50)
• Timing accuracy within 100ns of UTC
• PPS is controlled by special crytographic keys

11
Military GPS Receivers

• Small Lightweight GPS Receiver (Slugger)
• Most Models SPS
• Used during Desert Storm
• Precise Lightweight GPS Receiver (Plugger)
• Standard Handheld Unit
• PPS Capable
• Miniature Airborne GPS Receiver
• Standard Aircraft Unit

SLGR
MAGR
PLGR
12
Force XXI Battle Command Brigade and Below
(FBCB2)Overview

• Description
• Forms the principal Digital Command and Control
  System for the Army at Brigade and Below
• Consists of hardware and software integrated into
  the various platforms at brigade and below, as
  well as appropriate Division and Corps slices
  necessary to support brigade operations
• Interconnects platforms through a communications
  infrastructure called the Tactical Internet
  consisting of existing EPLRS and SINCGARS Radio
  nets to pass Situation Awareness data and conduct
  Command and Control

2179 FBCB2 Systems Fielded to 4th for FDD
13
ONE PLATFORMS WORTH OF FBCB2 DIGITAL COMPONENTS
SUPPORTING SITUATIONAL AWARENESS AND COMMAND AND
CONTROL
14
Common Message Functions (Create/Edit/Send/Manage)
Pull down menus allow the user to send various
reports or build graphical overlays. When a
report is sent, such as a Contact Report, the
software automatically updates all other
computers in the network with an enemy icon .
Similarly, a commander can build a set of
graphics depicting unit boundaries, friendly unit
locations, known enemy locations, etc and quickly
distribute this overlay around the battlefield.
Sending a message automatically updates all other
FBCB2s in the network.
15
Combat Messages Spot Report
This sample report provides details pertaining to
an enemy unit. Once again, information is
automatically shared with all others.
Enemy location can be quickly entered by clicking
the mouse cursor on the computer map where it is
located.
16
Advantages and Disadvantages of GPS
Limitations
Advantages

• All-weather
• Day and night
• Worldwide direct downlink
• Passive
• Common grid
• Restricted access
• Survivable
• Provides 3-D position and velocity

• Dependent on ground stations
• Jammable signal
• Line of Sight from GPS satellites

17
Summary

• GPS offers many advantages for navigation
• The GPS system consists of a Space Segment, a
  Ground Segment, and a User Segment
• Selective Availability ensures Authorized users
  can receive a highly accurate GPS signal while
  Non-Authorized users (potential adversaries) can
  be given a degraded signal
• The most common military GPS receiver is the
  PLGR, but many other receivers exist as well.
• GPS is evolving from a standalone capability into
  an integrated system called FBCB2.
• FBCB2 integrates GPS and a militarized GIS
  program to give commanders and soldiers increased
  situational awareness