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Panel 1 NPECAB. September 2007. Leadership Panel, Issue 1 Remove S/A Capability from System. Background Removal has been urged by independent Panels for over 10 years Capability is trivially defeated by GPS differential Systems (WAAS, NDGPS, etc.) It Flags the “Military Control of GPS”.

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panel 1 npecab

Panel 1NPECAB

September 2007

leadership panel issue 1 remove s a capability from system
Leadership Panel, Issue 1 Remove S/A Capability from System
  • Background
    • Removal has been urged by independent Panels for over 10 years
    • Capability is trivially defeated by GPS differential Systems (WAAS, NDGPS, etc.)
    • It Flags the “Military Control of GPS”

The Good News: It was Officially removed by Secretary England at the urging of Dr. Schlesinger and announced 18 September 2007

seattle raim availability comparison
Seattle RAIM Availability Comparison

SweetSpot

2 Degree Mask Angle

Standard 24 Satellite Constellation

prioritizing the big five goals for gps
Prioritizing the“Big Five”Goals for GPS
  • Assured Availability of GPS signals-Including impaired situations (mountains, urban areas, foliage, etc.) (Signal has to be broadcast and in view)
  • Resistance to Interference (RFI) (User must receive it)
  • Accuracy (Ranging Error and Geometry must meet need)
  • Boundedinaccuracy(Wild points limited by Good Geometry and bounds on ranging error)
  • Integrity - eliminating HMI, meeting required time to alarm (Satellite runaway must be very improbable)
the big five goals for gps
THE“Big Five”Goals for GPS
  • Assured Availability of GPS signals-Including impaired situations (mountains, urban areas, foliage, etc.)
    • Number of GPS Satellites/Geometry
    • Interoperability and Standardization with Galileo et al
  • Resistance to Interference (RFI)
    • Additional Satellite RF power and Frequency Diversity
    • More jam resistant GPS receivers
  • Accuracy
    • Require Prediction Accuracy (Satellite Clocks and Age of Update)
    • Good Satellite Geometry is essential
    • Augmentations: WAAS, LAAS,EGNOS, MSAS, NDGPS, PLs
  • Boundedinaccuracy to limit wild points
    • Concerned with the 1% or less “wild data points”
    • Good Satellite Geometry Coverage is Imperative
  • Integrity - eliminating HMI, meeting required time to alarm
    • RAIM
    • WAAS
    • Satellite Design – Self Checking

Three of top four Goals are driven by the number of satellites – hence DSB & IRT

30+X satellite recommendation

a caution the under emphasized goal
A Caution: The Under - emphasized Goal
  • For many users, accuracy is of less concern than the bounds on inaccuracy.
    • GPS errors do not follow a true Gaussian (called Normal) distribution, particularly regarding outliers
    • Need more emphasis on this element of the big 5.
  • We should insure that all improvements are backward compatible.
more observations
More Observations
  • Not practical for GPS to have service level based guarantees that are universally useful to all users
  • Perhaps a new paradigm of service is needed
    • Define component services (e.g. pseudorange accuracy) that will be exploited by all users to produce required service levels
    • Provide performance guarantees on components such that end users can derive meaningful performance measures in the context of their application
panel 1 meeting user needs with affordable progress recommendations
Panel 1: Meeting User Needs with Affordable Progress - Recommendations
  • Place GPS III quickly under contract with early delivery
  • Formally Commit to current Level of Service
  • Insure Affordability – enable service without brownouts
  • Place GPS signal and availability under a true National Committee Tied to Approval Authority(strong participation by users as well as government agencies e.g. RTCA, NSTAC)
the brownout danger
The Brownout Danger
  • Current GPS Average on-orbit life - 8.9 years
  • First IIF currently launch ready ICA 50%: February 2009
  • First GPS III currently available for Launch - December 2013

It is imperative the we avoid “GPS Brownouts”

Needed: Sustained, high-level supportfor earlier GPS III delivery and availability

overview from gps iii irt one element
Overview from GPS III IRT(one element)
  • A 30+X constellation is much more important & higher priority than Spot-Beams and Wide Band Crosslinks
    • Blindly pursuing all the current Requirements would be expensive, risky & late
    • Expensive, Complex Satellites will threaten schedule and, ultimately, the constellation size
    • Block size should be 8 to attain 30+X constellation
    • Requires Senior acceptance and direction
illustrating why current number of satellites is minimal courtesy gps world and john lavrakas
Illustrating why current number of Satellites is Minimal(Courtesy GPS World and John Lavrakas)
  • DOP is strongly driven by Masking Angle and number of satellites (the impaired user’s problem)
  • Above 10o, less than 30 satellites destroys accuracy and availability

The Knee

Monthly Availability of 24 sats 92 to 100%

DOP vs. Mask Angle (degrees) (June 6 2006)

a new development aircraft landing and relative raim
A New Development:Aircraft Landing and “Relative RAIM”
  • Provides the integrity to allow aircraft to
    • Land at “regional” airports in bad weather
    • Use lightly instrumented third-world landing fields with safety
  • Without any Ground Augmentation
  • Potentially helps the military “Bounded Inaccuracy” goal with a rigorous self check
  • Requires at least 30 satellites for reliable operation

RAIM – Receiver Autonomous Integrity Monitoring - Use of more than minimum (4) satellites to determine the navigation signal is within normal error bounds

background
Background
  • DSB Recommendations
    • To support all DOD users, & provide adequate signal availability in urban canyons, mountainous terrain (typical masking angles of 15to 20 degrees) the GPS constellation should be specified as 30 SVs plus adequate spares (30+X)
    • To insure affordability, constrain GPS III satellite size to enable dual launch (insure 30 SVs are attainable)
    • S/A capability-- no operational value: no further resources should be expended to place it on GPS III
reality check mask angle
Reality Check – Mask Angle
  • Extend right arm directly forward with thumb up
  • Close the hand and form a fist
  • The angle as seen from the bottom to the top of the fist is very close to 10 degrees

A 10 degree mask angle is totally unrepresentative of mountains or urban areas

14th af assessment of gps operations in iraq afghanistan feb 2006
14th AF assessment of GPS operations in IRAQ & Afghanistan -- Feb 2006
  • 14th AF Recent on-site Observations
    • Afghanistan
      • Poor Availability--degraded due to mountains (high masking angles)
      • Minimal RFI - terrain shielding
    • Iraq
      • Jamming/RFI ~85% known blue force interference 15% unknown
      • Number of GPS receivers Military & Civilian unknown - significant number of both
  • Availability Number one requirement
    • Solution-More visible satellites
  • Must solve the Jamming RFI Problem
    • Solution- improved UE [fixes already demonstrated]
why affordability is so critical
Why Affordability is so Critical

Military Opns

in Impaired

Areas

Clear Need for

“Specified”Constellation of > 30 Satellites

TheNeed

Civil A/C

Landing & ADS-B Integrity

Meet orExceed Current Capability

Or Inevitable Brownouts?

Budget Decisions

The PriceMust be Affordable

Dual Launch?(save

>$50M/sat)

Cost perSatelliteon Orbit

“Extra” Missions?

(900#Gorilla)

Battleship Galactica orAffordable First Step?

affordability recommendation
Affordability Recommendation
  • DOD should commit to providing a 30 Satellite constellation 98 % of the time and a 27 satellite constellation 100 % of the time
  • To insure that commitment is met, steps should be taken to resist escalating costs:
    • Specify Dual Launch
    • Eliminate modules not essential to the primary mission
    • Do not allow requirements creep to expand the IIIA design beyond the essential first step
panel 1 summary meeting user needs with affordable progress recommendations
Panel 1 Summary: Meeting User Needs with Affordable Progress - Recommendations
  • Place GPS III quickly under contract with early delivery
    • Provides significant improvements over IIF
    • Insurance against Brownouts (150 million users)
  • Formally Commit to current Level of Service
    • So Civil Users can take advantage of proven capabilities
    • e.g. 30 + x Satellites Geometrically Optimized for Users
    • Insure Military Availability in impaired regions
    • Meet the Projected Capabilities of Compass and Galileo
    • Support world-wide use to reduce Aircraft congestion (RRAIM)
  • Insure Affordability – enable service without brownouts
    • Avoid non-GPS “requirements” (NDS et. al.)
    • Dual Launch
    • Fund a sensible fast-track development
  • Place GPS signal and availability under a true National Committee Tied to Approval Authority(strong participation by users as well as government agencies e.g. RTCA, NSTAC)
    • Assures signal is truly compatible and Maximizes Usefulness