panel 1 npecab
DESCRIPTION
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”. - PowerPoint PPT PresentationTRANSCRIPT
Panel 1NPECAB
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”
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
2 Degree Mask AngleStandard 24 Satellite Constellation
SweetSpot
Prioritizing the “Big Five” Goals for GPS
1. Assured Availability of GPS signals-Including
impaired situations (mountains, urban areas, foliage,
etc.) (Signal has to be broadcast and in view)
2. Resistance to Interference (RFI) (User must
receive it)
3. Accuracy (Ranging Error and Geometry must meet need)
4. Bounded inaccuracy (Wild points limited by Good
Geometry and bounds on ranging error)
5. Integrity - eliminating HMI, meeting required
time to alarm (Satellite runaway must be very improbable)
THE “Big Five” Goals for GPS1. 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
2. Resistance to Interference (RFI)– Additional Satellite RF power and Frequency Diversity– More jam resistant GPS receivers
3. Accuracy– Require Prediction Accuracy (Satellite Clocks and Age of Update)
– Good Satellite Geometry is essential– Augmentations: WAAS, LAAS,EGNOS, MSAS, NDGPS, PLs
4. Bounded inaccuracy to limit wild points– Concerned with the 1% or less “wild data points”– Good Satellite Geometry Coverage is Imperative
5. 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
• 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
• 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
1. Place GPS III quickly under contract with early
delivery
2. Formally Commit to current Level of Service
3. Insure Affordability – enable service without
brownouts
4. 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
• 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
Needed: Sustained, high-level supportfor earlier GPS III delivery and availability
It is imperative the we avoid “GPS Brownouts”
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)
• 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
Monthly Availability of 24 sats 92 to
100%
DOP vs. Mask Angle (degrees) (June 6 2006)
The Knee
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
operationRAIM – Receiver Autonomous Integrity Monitoring
- Use of more than minimum (4) satellites to determine the navigation signal is within normal error bounds
Integrity for ATC and Aircraft Landing using Relative RAIM
The Military Need for 30 + X
Summary
Background
• DSB Recommendations– To support all DOD users, & provide adequate
signal availability in urban canyons, mountainous terrain (typical masking angles of 15 to 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
• 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
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 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
Availability Number one requirement
•Solution-More visible satellites
• Must solve the Jamming RFI Problem
• Solution- improved UE
[fixes already demonstrated]
Military Opns
in Impaired
Areas
Civil A/C Landing &
ADS-B Integrity
Clear Need for
“Specified”Constellation
of > 30 Satellites
TheNeed
Dual Launch?
(save>$50M/sat)
“Extra” Missions?
(900#Gorilla)
Cost per
Satellite
on Orbit
The Price
Must be Affordable
Budget Decisions
Battleship Galactica orAffordable First Step?
Meet orExceed Current
CapabilityOr Inevitable Brownouts?
Why Affordability is so Critical
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
1. Place GPS III quickly under contract with early delivery– Provides significant improvements over IIF– Insurance against Brownouts (150 million users)
2. 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)
3. Insure Affordability – enable service without brownouts– Avoid non-GPS “requirements” (NDS et. al.) – Dual Launch– Fund a sensible fast-track development
4. 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