Introductory Comments

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

Context: GPS “Big Five” Objectives Developed by the GPS IRT - generally accepted 1.Assured Availability of GPS 2.Resistance to Jamming and Interference 3.Accuracy (Usually the 50 th percentile) 4.Bounded inaccuracy to limit “wild points” (Usually the 95 th or 99 th percentile) 5.Integrity - eliminating erroneous signals

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 50 th percentile) – Constellation Size and Geometry – More and improved Signals – Improved Ranging Errors (satellite clocks) Bounded inaccuracy to limit “wild points” (Usually the 95 th or 99 th percentile) –Same as Accuracy, but usually more stringent Integrity - eliminating erroneous signals –Independent Cross checking (WAAS and EGNOS et. al.) –Satellite Self Checking

GPS “Big Five” Objectives What can we do to stay world leaders? 1.Assured Availability of GPS –30+X significantly increases availability in impaired operations –Moving ahead now on Block IIIA reduces risk of a significant gap 2.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.) 3.Accuracy –30+x is a significant geometry improvement over nominal 24 –New Military and Civil signals 1.more accurate ranging determination and resistance to multipath 2.Better clocks enable more accurate signal in space 4.Bounded inaccuracy to limit collateral damage and fratricide –30+X provides redundant crosschecking by users (RAIM) 5.Integrity - eliminating erroneous signals –Satellite checking for runaway clocks and “evil” waveforms

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)