October 08 Interim Report Big 5 and MOEs 1 GPS “Big Five” contribution to Users Needs AN UPDATE Prof. Brad Parkinson Draft Developed for IRT – August 2008 Thanks to Col. Dave Madden and Aerospace for help, Particularly Tom Powell and Paul Massatt Also FAA with Sam Pullen and Todd Walter Showing Dependence of User Measures of Effectiveness (MOE) on GPS System Design & Design Decisions

October 08 Interim Report Big 5 and MOEs 2 The IRT “Big 5” – Essential GPS PNt Characteristics A Bridge between User’s MOE and GPS System Design 1.Assured (Geometric) Availability of GPS signals 2.Resistance to (Deliberate or Unintentional) Interference 3.Accuracy of User’s GPS Position (After satisfying #1 and #2) 4.Bounded inaccuracy –Limiting potential for very large errors (Fratricide or Collateral Damage) 5.Integrity – Identifying and eliminating the non-normal GPS system or local errors (e.g. extreme user multipath or runaway clocks).

October 08 Interim Report Big 5 and MOEs 3 Performance Envelope Conceptual Examples Current GPS Capabilities (30+ Sats) Current GPS Specification (e.g Sats) Needs for SDB (Target Designation in Visibility Impaired Region) Cat III Aircraft Landing (Integrity – Time to Alarm or Availability) Potential GPS Enhancements Potential GPS Augmentations The “Envelope” “Envelope” Missions FAA ATC Modernization ADS-B

October 08 Interim Report Big 5 and MOEs 4 Envelope Examples of Uses (Summarize A, B, and D) Military Uses M1. Use of Small Diameter Bomb in region where ground target locator has impaired visibility (e.g. mountainous terrain or urban street) (In Mission A) M2. Delivering weapons close to friendly troops, or close to sensitive “don’t hit” locations (In Mission A) M3. Operating with impunity in the vicinity of high-power (or multiple, distributed) Enemy Jammers (In Mission A) M4. Operating in mined land or restrictive sea areas Civilian Uses C1. Precision Aircraft Approach and Landing (Up to Cat III) demanding integrity (Mission B – includes a military mission) C2. First Responder PNT in Urban Area (Mission C) C3. Precision Survey using GPS carrier Phase C4. Use of GPS ADS-B mandated for future ATC System – improving separation distances (Mission D) C5. Resistance to inadvertent GPS interference or deliberate sabotage (see military #3) C6. Obscuration in Open Pit Mining

October 08 Interim Report Big 5 and MOEs 5 Mission Trade Analysis Mission A. Air Dropped Bomb against Ground located target Want to show effect of GPS Decision Maker’s Trades on Measures of Effectiveness Note: this is illustrative of the technique and approach It does not incorporate actual weapons system’s data Sensitive results are presented in Relative Terms UPDATE

October 08 Interim Report Big 5 and MOEs 6 Afghanistan in this Analysis Observer is assumed to be part way up Mountain (Red Dot) Slope assumed at 45 to 60 degrees (could be steeper) Target Building is on other side of Valley

October 08 Interim Report Big 5 and MOEs 7 Constraints and Assumptions Within current Availability In Red, the next step possibilities – also analyzed Terrain – Valley in Afghanistan mountains, –Observer on side of 45 (or 60) degree slope Obscuration ~40% Observer Laser Sight: –Gyrocompass North- –Azimuth - 3 mils, –Elevation 3 Mils –Range 3 Meters Observer GPS –2.6 meter multipath-limited receiver (1 meter multipath narrow tracking correlator) – 0.75 meter receiver noise Target –1 km away GPS Constellation –18, 21, 24, 27, 30, 33, 36 considered with 1,2, or 3 satellites randomly out –URE: Block II 0..57m, Block III 0.25m Bomb/Weapon –Same Constellations considered –3.5m Guidance error Guidance Error 1.0m –GPS 0.8m noise, negl. multipath URE as above –Vertical at impact Jamming interference –Assume a hostile 10W noise Jammer

October 08 Interim Report Big 5 and MOEs 8 Buildings on a Mountain Road Target is Largest Building Numbers in Boxes are the number of Hits Road

October 08 Interim Report Big 5 and MOEs 9 Observer on Slope of 45 Degrees

October 08 Interim Report Big 5 and MOEs % Circle - Only 1 in 1000 exceeds 50% Circle Half in, Half out. Usually called CEP – a poor measure of effectiveness 95 % Circle Should approximate Target size, (for first round effectiveness) Sometimes called “2d” bldgldgbldgldg

October 08 Interim Report Big 5 and MOEs 11

October 08 Interim Report Big 5 and MOEs 12

October 08 Interim Report Big 5 and MOEs 13

October 08 Interim Report Big 5 and MOEs 14 Observer on Slope of 60 Degrees

October 08 Interim Report Big 5 and MOEs 15

October 08 Interim Report Big 5 and MOEs 16

October 08 Interim Report Big 5 and MOEs 17

October 08 Interim Report Big 5 and MOEs 18 Selected Civil “Envelope” Missions Precision Approach and Landing (Mission “B”) – Representative US Airports – Desire Availability of >99.5% (99.9% ?) Advanced Air Traffic Control System (Mission “D”) – GPS Based – Uses Automatic Dependent Surveillance Beacon (ADSB) – Integrity Guaranteed - Issue is Geographic Coverage for 99.5% availability

October 08 Interim Report Big 5 and MOEs 19 Constraints and Assumptions for Mission B – CAT III Precision Landing Terrain – Civil Airports and Military Airfields Aircraft guided down to 200’ HAT CAT I Decision Height solely by GPS Local Area Augmentation System (LAAS) fielded at airport/airfield where landing takes place –Vertical guidance is limiting factor From 200’ to 100’ HAT, aircraft guided by LAAS with airborne inertial system as backup Below 100’ HAT (above runway threshold), aircraft primarily guided by radar altimeter GPS Constellation –21, 24, 27, 30, 33, 36 considered with 1,2, or 3 satellites randomly out (cycle through all outage permutations) –URE: dictated by LAAS ground and airborne error models RF interference –When present, assume unintentional ground-based RF interference sufficient to make satellites below 10, 15 deg. elevation (TBC) unusable

October 08 Interim Report Big 5 and MOEs 20 Four Measures of Effectiveness (MOEs) for Mission “B” – Cat III Landing MOE 1: Long-term probability that CAT III operation is available (without RF interference) Trade I – No. of GPS Satellites in Constellation MOE 2: Longest interval that CAT III operation is unavailable (without RF interference) Trade I – No. of GPS Satellites in Constellation MOE 3 : Loss-of-continuity probability when RF interference is suddenly introduced Trade II - Techniques to reduce RF interference vulnerability MOE 4: Availability probability when RF interference persists Trades I and II

October 08 Interim Report Big 5 and MOEs 21 Results for 12 Airports Max. Outage Duration (min) Note Min. Avail. on Plot 99.9 % Availability Threshold Availability Results for IRT “Baseline” 24-SV Constellation – 1,2, or 3 GPS outages (Slide 1 of 2)

October 08 Interim Report Big 5 and MOEs 22 Availability Results for IRT “Baseline” 24-SV Constellation (Slide 2) Max. Outage Duration (min) SV Out (4-min updates) 2 SV Out (2-min updates) 1 SV Out (1-min updates) 0 SV Out (15-sec updates)

October 08 Interim Report Big 5 and MOEs 23 Availability Results for IRT 30-SV Constellation Max. Outage Duration (min) Note Min. Avail. on Plot

October 08 Interim Report Big 5 and MOEs 24 Comparison of CAT III Availability for All Six IRT Constellations (21 – 36 SV’s) 0 SVs Out1 SV Out2 SVs Out3 SVs Out Number of SV’s Unhealthy Un-availability IRT 21-SV IRT 24-SV IRT 27-SV Desired Availability 99.9% IRT 33-SV IRT 36-SV IRT 30-SV

October 08 Interim Report Big 5 and MOEs 25 To compare to IRT constellations, a recent GPS constellation almanac (Week 465, 25 July 2008) was downloaded and simulated. Results for two cases shown on the following slide: –Optimistic – use all 31 satellites listed in almanac (24 “primary”  7 “spare” orbit slots) –Realistic: remove 5 satellites in “spare” orbit slots that are older than 15 years of age »Retain use of 2 satellites in “primary” orbit slots that exceed 15 years of age »26 satellites are used (24 “primary”  2 “spare” orbit slots) Simulations with Current GPS Constellation

October 08 Interim Report Big 5 and MOEs 26 Comparison of CAT III Availability for IRT and Current Constellations 0 SVs Out1 SV Out2 SVs Out3 SVs Out Number of SV's Unhealthy Un-availability IRT 36-SV IRT 30-SV IRT 21-SV IRT 24-SV IRT 27-SV Current/Optimistic (31-SV) Desired Availability 99.9% IRT 33-SV Current/Realistic (26-SV) Current/Optimistic (31-SV)

October 08 Interim Report Big 5 and MOEs 27 More availability results to follow… Results now available for all SV constellations for no-RFI case Now experimenting with best ways to plot these results Status of CAT III Analysis

October 08 Interim Report Big 5 and MOEs 28 Mission D – GPS-Based ADS-B Support of Air Traffic Control Many aircraft in flight Each equipped with GPS/SPS and/or WAAS Each equipped with ADS-B transponder to share GPS- based “PVT” information Airport C ATC Tower Airport B FAA ARTCC Airport A ATC Tower ADS-B PVT

October 08 Interim Report Big 5 and MOEs 29 Perfect Constellation: Comparison of GIC (WAAS) and RAIM Integrity Techniques (Table with Numerical Values) Satellite Constellation Architecture WAAS Integrity100% RRAIM (300-sec coasting) 76.1%99.6%100% ARAIM44.7%94.1%100% Fraction of Airspace (inside ± 70 deg. Latitude) with ≥99.5% availability of support for Precision Approach to 200’ Height Above Terrain (Like CAT I)

October 08 Interim Report Big 5 and MOEs 30 Realistic Constellation Comparison of GIC (WAAS) and Self-Integrity (RAIM) Techniques (Table with Numerical Values) Satellite Constellation Architecture 24 minus significant SV 27 minus significant SV 30 minus significant SV WAAS Integrity 86.6%97.8%100% RRAIM (300-sec coasting) 28.0%52.3%93.9% Absolute RAIM7.8%30.6%90.5% Fraction of Airspace (inside ± 70 deg. Latitude) with ≥99.5% availability of support for Precision Approach to 200’ Height Above Terrain (Like CAT I)

October 08 Interim Report Big 5 and MOEs 31 Summary and Path Forward Evaluation of civil missions/uses B and D (CAT III precision landing and ADS-B support of ATC) will be conducted using common simulation approach –CAT III application is more clear-cut (based on use of already-defined single-frequency LAAS) –ADS-B application has more options and trades The simulation needed to evaluate Mission B has been built and run for IRT constellations and for two variations of recent GPS Week 465 broadcast almanac

October 08 Interim Report Big 5 and MOEs 32 Decision # I. The Number of GPS Satellites Current “Requirement” – 24 ( 21 plus three active spares) On orbit are 31but not optimal –Much improved geometric availability - Users now expect this performance –Paired Orbits – not optimal for 30 (ready for Failure) Many studies have suggested the “knee in the curve” for user availability is 30 to 36 –Critical users – those with impaired sky visibility or extreme integrity req. A key to increasing commitment to 30 + X is on-orbit cost of Satellites –Major driver Additional Payloads (reduce size, weight, power and complexity) –Cost savings opportunity - dual launch Decision: A National commitment to increased number of SVs –Civil users could have significantly improved availability –Military Users more effective in impaired situations

October 08 Interim Report Big 5 and MOEs 33 Conclusions The concept of “Envelope” missions places focus on those missions that really drive GPS system design and illuminate trades for the decision makers We have shown a Process : –relates GPS System Design Trades to Measures of Effectiveness (MOE) –Closely related to the “Big 5 GPS Characteristics” but adds the advantage of quantification MOEs are very mission specific – relate to particular use and/or users Additional “Envelope” missions are suggested as worthy of further MOE analysis

October 08 Interim Report Big 5 and MOEs 34 PL Fundamental Issues – Operations Most impaired users are in “harms way” – Placing PLs in the Afghan Mountains not plausible One PL usually only benefits a narrow geographic area Support for PL requires monitoring GPS receivers must be specially configured to handle PL signal –Near-Far problem Airborne PLs suffer degraded accuracy, and complex support architecture

October 08 Interim Report Big 5 and MOEs 35 Comment on MOE 1: The Accuracy Payoff Reducing error by 3 improves P K by up to 9 CNN wars dictate reduced collateral damage – the stray bomb is important Improve 1 st round effectiveness = less US attrition. Sorties to destroy = ~ 1/ P R Issue: Need both TLE and WLE accuracy