GPS Modernization

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Presentation GNSS 4.2 by H. Cabler
ICAO CAR/SAM ATN/GNSS SEMINAR
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Modernization History

• Need for GPS Modernization recognized by US as
  GPS entered Full Operational Capability (1995)
• Recognized growing importance of GPS to both
  sectors
• National Policy imperative to enhance GPS as
  single world standard
• Better, more reliable civilian service
• Need to rethink GPS architecture for the future
• Multiple studies indicated diverse set of needs
• New signals, Higher Power, Greater Accuracy
• Greater focus on dual-use nature
• System Integrity, Survivability, and Prevention
  of hostile use
• Better Spectrum Management

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Background

• 1996 Presidential Decision Directive (PDD) and
  1998/99 Vice Presidential announcements committed
  US to modernization and improvement path
• Selective Availability (SA) turned to zero NLT
  2006
• Two new civil signals and new military signals
• Free world-wide use
• Move from studies to action initiated in FY 2000
• SA Set to zero in May 00
• directed changes to existing and future
  satellites
• IIF program terminated at 12 satellites and GPS
  III development began

Modernization Now in Full Swing
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GPS Modernization at a Glance
Increasing System Capabilities Increasing
Civil/Defense Benefit
Full Civil Rqmts Addl Capabilities
New Civil Signal L5
L2C on L2
Basic GPS
SA Set to 0
GPS III
GPS IIR-M, IIF

• GPS-III
• Increased power (20dB)
• Increased Accuracy
• Greater Availability
• Controlled Integrity
• Greater Survivability

GPS IIA/IIR

• IIR-M Improved on all IIA capabilities and
  added
• 2nd Civil Signal on L2
• New L1 L2 M-Code
• IIF IIR-M capability and
• Add 3rd Civil Signal on L5

• Standard Service (100 m)
• Precise Service (16 m)
• Two Nav frequencies
• L1 Civil (C/A) Precise
• code, Navigation
• L-2 P-code Nav

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New Civil Signals

• Many consider setting SA 0 as the 1st step in
  modernization
• New Signals can be considered the 2nd/3rd Steps
• Civil Users Currently Limited to One GPS Signal
• C/A-code at L1 frequency (1575.42 MHz)
• Adding a Second Civil Signal
• C/A-type code at L2 frequency (1227.60 MHz)
• Adding a Third Civil Signal
• P-type codes at L5 frequency (1176.45 MHz)
• Higher power signal, intended for precision
  navigation

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SA Set to Zero on 2 May 2000

• Selective Availability (SA) Intentional
  Degradation
• President decided to discontinue SA to aid
  peaceful civil users
• Civil user accuracy dramatically increased on 2
  May 2000

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Block IIR Modernization

• Pre-Modernization/IIR
• Heritage Signals
• L1 C/A
• L1, L2 P(Y)
• On Orbit Life
• 10.6 Years MMD

• Post Modernization/IIR-M
• Modernized Signals
• Flexible, Higher Power
• L1 C/A, L2C (or C/A)
• L1, L2 P(Y)
• L1, L2 M-Code)
• On-Orbit Life
• 8.6 Years MMD

Design Life/MMD analysis completed Nov 01.
L2 Second Civil signal design supports varying
code length and data structure
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Block IIF Modernization

• Post Modernization
• Modernized Signals
• Flexible, Higher Power
• L1 C/A, L2C
• L1, L2 P(Y)
• L1, L2 M-Code
• L5 Third Civil
• Design Life
• 12 Years
• 10 Year MMD

• Pre-Modernization
• Heritage Signals
• L1, L2 C/A
• L1, L2 P(Y)
• Design Life
• 15 Years

L2 Second Civil signal design supports
varying code length and data structure L5
Third Civil signal at -154dBw
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New Civil Signal Roll-Out

• Second Civil Signal (L2C) - Block IIR-M
  Satellites
• First launch in 2003, then every satellite
  thereafter
• Provides a redundant signal for civil users
• Improved continuity in case L1 signal reception
  is lost
• Improved accuracy via dual-frequency ionosphere
  correction
• Wide-lane for extremely-precise local area
  differential GPS
• Third Civil Signal (L5) - Block IIF Satellites
• First launch in 2005, then subsequent satellites
  thereafter
• Provides redundant dual-frequency capability for
  civil users
• Improved continuity in case L1 or L2 signal
  reception is lost
• Improved accuracy via triple-frequency ionosphere
  correction
• Tri-lane for ultra-precise local area
  differential GPS

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New Capability Schedule
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FY
1st GPS-III SV
System Milestones
1st L2C SV
L2C IOC
L2C FOC
1st L5 SV
GPS-III FOC
L5 IOC
L5 FOC
GPS-III IOC
Space Segment
Heritage Launches
Modernized (IIR-M/IIF) Launches
1st IIR-M
1st IIF
GPS III Launches
GPS III Launches
EMD
1st GPS III
SAASM
M-Code
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GPS III System Vision
The GPS III System
Second Civil Signal
Third Civil Signal

• Relook at Entire GPS Architecture to
• Achieve long term GPS performance goals
• Reduce long term total ownership costs
• Ensure GPS III is Synergized with
• Military and Civil Needs/Systems
• Possible augmentation opportunities
• Build Best GPS for the Next 30 Years

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GPS III Addresses MultipleGPS Needs

• Significantly Increased Integrity
• Crucial for anticipated civil aviation uses
• Also important for military use
• High level of Signal Availability
• Equally important to both military and civilian
• Significantly Increased Accuracy
• Driven by evolving nature of warfare and civil
  uses
• Additional GPS needs Future flexibility, nav
  related messaging, reprogramability

These Needs not able to be addressed without
significant architectural change
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GPS III Integrated Approach

• GPS Originally Designed without benefit of an
  Established User Base
• Civil Users Previously Solicited for Suggested
  Changes to Existing System to Meet their Needs
• GPS III has Novel Approach for Integrating Needs
  of the DoD, DOT, FAA
• Just completed System Architecture and
  Requirements Definition phase gathered and
  identified future requirements
• Interagency Forum for Operation Requirements
  created to identify and assemble new requirements
  for GPS
• Civil and military requirements to be approved in
  totality by joint committee
• Coast Guard Navigation Center soliciting
  requirements via website

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Stressing Civil Missions
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Other Civil Missions (over 140 total)
Other Civil Missions
Stressing Civil Missions

• Category IIIB/C instrument landing at approved
  airport
• Precision automatic highway vehicle guidance
  (including collision avoidance), including in
  urban canyon conditions
• Mobile personal systems wireless communications
  synchronization for advanced performance
  signaling protocols
• Computing/communications network synchronization
• Electric power grid synchronization
• Precision construction equipment guidance
• Construction surveying
• Crustal motion monitoring
• Weather monitoring (tropospheric water content)
• Scientific instrument synchronization
• Open loop antenna pointing for mobile satcomm
  users, other instrument pointing
• Hiker navigation
• Civilian spacecraft position and attitude
  determination for sensor pointing

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GPS III Increased Capability

• Assured Delivery of GPS Signals
• Higher Power Military Civil Signals
• Higher Accuracy Service for All Users
• Increased Integrity Inherent in GPS

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GPS III Assured Delivery

• Dual-Use GPS is more than just Adding Civil
  Signals
• Assuring availability and continuity of signals
• Realization that GPS is considered a Critical
  Part of Worldwide Infrastructure
• Availability/Continuity Key Factors in GPS III
  Design
• Crosslink architecture
• Number of orbital planes
• Number of satellites
• Sparing strategy
• Replacement strategy
• Control segment

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GPS III Increased Accuracy

• Augmented and standalone missions identified that
  require more accuracy than modernized GPS
• Signal-in-space improvements must keep pace with
  those in users equipment
• Advanced technology clocks
• Inter-satellite ranging
• Improved ephemeris and orbital models
• Age of Data reduction and more timely updates via
  crosslinks

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GPS Accuracy
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GPS III Increased Integrity

• Aviation applications one of key drivers
• GPS III architectural changes
• Improved monitoring and reporting
• Planned interfaces between GPS and augmentations
• Potential for meeting broad array of civil and
  military needs via GPS alone

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Sufficient Means of Navigation?

• Sufficient to be used anywhere, anytime
• Without precluding use of other systems or
  augmentations
• Without requiring use of other systems or
  augmentations
• Except for most demanding applications (LAAS)
• With assured delivery
• Availability and continuity (and higher power)
• With high accuracy
• With high integrity

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Ground Augmentation

• By itself, GPS III will have very good Accuracy
  and Integrity
• Good enough for most navigation applications
• Ground Augmentation Gives Major Improvements
• For Ultra High Accuracy
• 1 m with Local Area Differential GPS (LADGPS)
• 1 cm with Real-Time Kinematic (RTK)
• For Ultra High Integrity
• ?1-1x10-9/operation or even better is achievable
• Precision Landing Needs High Accuracy/Integrity
• Prime example of GPS ground augmentation system
  usage
• Civil Local Area Augmentation System (LAAS)

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Challenges

• Maintaining a healthy constellation while adding
  system capabilities
• Constellation sustainment strategies
• Operational Control Segment (OCS) upgrades
• Testing / validating new signals - design and
  operations
• Transition to modernized OCS
• Spectrum Protection
• International Cooperation

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International Cooperation

• Need a strategic view for US interaction with
  Galileo
• Work the policy and technical issues on how these
  two system can coexist and leverage one another
• Opportunity is now for us to begin working to
  ensure a single, integrated Navigation service
• Improves civil aviation, interoperability, and
  spectrum protection
• Will save money if done properly
• GPS III Acquisition effort is the right place to
  push for this to happen

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Summary

• GPS Modernization activities well underway
• GPS Modernization offers superb opportunity to
  satisfy both military requirements and civil
  needs
• GPS III exploring complementary DoD/civil
  augmentation opportunities
• Working through challenges
• GPS III Architecture Working hard toward a
  robust, supportable, flexible, international
  capability for the next 30 years