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

2. 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

3. Modernization Now in Full Swing
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

4. GPS Modernization at a Glance
Increasing System Capabilities
Increasing Civil/Defense Benefit
Full Civil Rqmts
Add’l 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
GMSP concept is afforded by GPS-III modernization. As a GPS-III augmentation alternative, GMSP may provide a more efficient way to satisfy multiple space needs.
GPS IIA/IIR
Standard Service (~100 m)
Precise Service (~16 m)
Two Nav frequencies
L1: Civil (C/A) & Precise
code, Navigation
L-2: P-code Nav
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

5. 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 ( MHz)
Adding a Second Civil Signal
C/A-type code at L2 frequency ( MHz)
Adding a Third Civil Signal
P-type codes at L5 frequency ( MHz)
Higher power signal, intended for precision navigation

6. 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

7. 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

8. Block IIF Modernization
Pre-Modernization
Heritage Signals
L1, L2 C/A
L1, L2 P(Y)
Design Life
15 Years
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
* L2 Second Civil signal design supports varying code length and data structure
** L5 Third Civil signal at -154dBw

9. 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

10. New Capability ScheduleFY 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19
1st GPS-III SV
System
Milestones
1st
L2C SV
1st
L5 SV
L2C
IOC
L2C
FOC L5
IOC L5
FOC
GPS-III
IOC
GPS-III
FOC
Space Segment
Heritage Launches
Modernized (IIR-M/IIF) Launches
1st IIR-M
1st IIF
EMD
GPS III Launches
GPS III Launches
1st GPS III
SAASM
M-Code

11. GPS III System Vision The GPS III System Second Civil Signal
Third Civil Signal
1 ON
menu 3 2
Rockwell 4 5 6
WPT 7
POS 8
NAV 9
MARK
CLR
OFF
LOCK
NUM
FIX FOM 1
EL ft
W 091* 38’ ”
N * 01” ”
ZEROIZE
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

12. GPS III Addresses Multiple GPS 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

13. 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

14. Stressing Civil Missions. . .
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

15. 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

16. 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

17. 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

18. GPS Accuracy
This chart depicts how Signal in Space pseudorange accuracy has evolved during the past six years and projected accuracy with AII and GPS III.
AII = Accuracy Improvement Initiative. Includes Control segment improvements and integration of NIMA ground stations.
This is really PPS accuracy. Today, the accuracy is 6 m in the SPS Performance Standard.

19. 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

20. 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

21. 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)

22. 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

23. 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

24. 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