Interchangeability and CARS

1. Any Four Will Do 1 Interchangeability and CARS Bradford ParkinsonStanford University

2. Any Four Will Do 2 What’s Next?

3. Any Four Will Do 3 PNT to Explode with Opportunities

4. Any Four Will Do 4 International Augmentations

5. Any Four Will Do 5 New Signals are On the Way

6. Any Four Will Do 6 Summary - Spectrum of Modernized GPS Signals

7. Any Four Will Do 7 Coming: a Plethora of Signals

8. Any Four Will Do 8 Latest Signal Verified – L5

9. Any Four Will Do 9 Levels of Cooperation - New Systems:Can’t we just get along? Degrees of “Getting Along” Compatible Lets not hurt each other Interoperable I’ll try yours, you can try mine Interchangeable Any four will do

10. Any Four Will Do 10 GPS and Galileo/Compass/GLONASS-The Users Viewpoint Real Measure: Interchangeability “Mix and Match” with the same ranging accuracy Enabled by L1C - defined, implemented, and operable – including all details Seamless WAAS/EGNOS/+ ? True clock Synchronization (Common Clock) and common grid Payoff – Availability, Accuracy and Robustness for  Worldwide Users

11. Any Four Will Do 11 Achieving Interchangeability Simplest: Common Clock and Geodetic System Probably Implies a common Control System Nationalistic Resistance A New Proposal – Cross-Augmentation Reference System (CARS) Each Satellite Broadcasts WAAS like Corrections to allow it to be seamlessly operated as a part of the “other” constellation

12. Any Four Will Do 12 Three levels of “WAAS-like Corrections” Correction for ephemeris and specific satellite clock Implies frequent upload capability Correction for satellite clock alone Geodetic correction assumed constant Intersystem time calibration (sub-nano-second) Assumed very slowly changing

13. Any Four Will Do 13 GPS/Galileo CARS Example– Cross Augmentation Reference System GPS Monitor Stations track Galileo satellites (L1C) Form WAAS-like Corrections for GPS satellites to operate as Galileo Ranging sources  (Clock and Position – Include integrity?) Include corrections as part of the GPS message Result: GPS satellite is seamlessly useable as a part of the Galileo Constellation

14. Any Four Will Do 14 CARS : GPS/Galileo ExampleFirst Step: Monitor the “other” constellation signals

15. Any Four Will Do 15 CARS : GPS/Galileo ExampleSecond Step: Send Augmentation Corrections to Each “own” satellite to allow it to be “seen” (used) as a member of the other constellation

16. Any Four Will Do 16 And Galileo would do the same for GPS (etc. for other GNSS Systems) Advantages: Satellites are truly Interchangeable Avoids issue of which time or which Geodetic System Very Low Rate message, low overhead Very efficient – corrections broadcast only for the satellite being used Each Satellite Provider has some control over use of their system User can have highly accurate PNT in coordinates of their choosing

17. Any Four Will Do 17 Unintended Consequences? Each Constellation forced to be smaller? Still need core capability to operate alone? Military cannot use for “Fire” clearance – Sky impaired warrior not helped Next Gen (FAA) still needs MOPS – May take a long time with Galileo Misleading Information Cross Augmentation Bit in message?

18. Any Four Will Do 18 Implementation of CARS Bi-Lateral Agreements Could be done experimentally on a unilateral basis Technical Working Group to adapt WAAS or EGNOS-like format for message Which level and frequency of update? Include Integrity? Ionospheric correction probably not necessary

19. Any Four Will Do 19 Conclusion We are entering an era with incredible opportunities in Worldwide PNT With a concerted effort of cooperation, all users should receive benefits:  economic, safety and convenience The ultimate goal is interchangeability CARS would enable this

20. Any Four Will Do 20 Notes Time only: Phi, Phidot, and tzero System to system time only Saves a calibrating satellite Unintended consequences Need less satellites? Military Next Gen Limited Upload Capability