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Introductory Comments

This article discusses the current status of the GPS constellation and the need for enhancements to ensure assured availability, resistance to jamming, and improved accuracy. It also addresses the concerns of GPS brownouts, affordability, and potential interference issues.

edwardbarrett
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Introductory Comments

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Presentation Transcript

  1. Introductory Comments

  2. Selected Background • Constellation (Currently ~29 on orbit) • Average Age on orbit about 9 years • IIF #1 not yet through Thermal Vac (Procuring 12) • Remaining IIR and IIRM’s are available • DoD commitment is for 21 plus 3 orbiting spares • Block IIIA (Launch 2013?) • Now in System Design Review • RFP not released – Apparently held up in Pentagon • DSB • Recommended the constellation be fixed at 30 plus spares

  3. Context: GPS “Big Five” ObjectivesDeveloped by the GPS IRT - generally accepted • Assured Availability of GPS • Resistance to Jamming and Interference • Accuracy(Usually the 50th percentile) • Bounded inaccuracy to limit “wild points” (Usually the 95th or 99th percentile) • Integrity - eliminating erroneous signals

  4. Attaining the GPS “Big Five” Objectives: The Main Drivers • Assured Availability of GPS • Constellation size and Reducing Outages • Resistance to Jamming and Interference • Multiple Signals, more EC Power, Improved UE • Accuracy(Usually the 50th percentile) • Constellation Size and Geometry • More and improved Signals • Improved Ranging Errors (satellite clocks) • Bounded inaccuracy to limit “wild points” (Usually the 95th or 99th percentile) • Same as Accuracy, but usually more stringent • Integrity - eliminating erroneous signals • Independent Cross checking (WAAS and EGNOS et. al.) • Satellite Self Checking

  5. GPS “Big Five” ObjectivesWhat can we do to stay world leaders? • Assured Availability of GPS • 30+X significantly increases availability in impaired operations • Moving ahead now on Block IIIA reduces risk of a significant gap • Resistance to Jamming and interference • More Earth Coverage signal power- • Diversified “all signal payload” provides alternative, possibly un-jammed channels • Adding the new Galileo/GPS signal L1C • Augmenting GPS with dissimilar Positioning Capability • Improved User Equipment for critical applications (e.g. beam steering antennas etc.) • Accuracy • 30+x is a significant geometry improvement over nominal 24 • New Military and Civil signals • more accurate ranging determination and resistance to multipath • Better clocks enable more accurate signal in space • Bounded inaccuracy to limit collateral damage and fratricide • 30+X provides redundant crosschecking by users (RAIM) • Integrity - eliminating erroneous signals • Satellite checking for runaway clocks and “evil” waveforms

  6. My three largest concerns: • Avoiding GPS Brownouts – The need for proceeding immediately with IIIA • Keeping IIIA simple and affordable Avoiding requirements creep: developing on time and budget • Avoiding/mitigating Interference (need for contingency augmentation - eLORAN)

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