Need for a IGS realtimenear realtime ionospheric product Tim FullerRowell, Mihail Codrescu, Eduardo

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Need for a IGS real-time/near real-time
ionospheric product?Tim Fuller-Rowell, Mihail
Codrescu, Eduardo Araujo-Pradere NOAA Space
Weather Prediction Center and/or CIRES
University of Colorado
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Space Weather Prediction CenterNational Weather
ServiceBoulder, Colorado
24/7 Space Weather Operational Center The
nations official provider of real-time space
weather alerts, warnings, and products
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Targeted Users and Parameters

• GPS positioning and navigation - iono TEC
  correctors
• Satellite communications - iono irregularities
• HF communications - absorption, ray tracing
• Commercial Airlines
• Satellite environment, drag, and re-entry
• TEC, 3D Electron Density, ?Ne, ?, O/N2
• Specification and Forecast

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• US-TEC Target Users
• Positioning and Navigation community
• Collaboration between SWPC, NGS, FSL, and NGDC
• Kalman filter over CONUS ground-based GPS data,
  IRI background model, solve for receiver biases
• 15-minute cadence
• 15 to 30 minute latency
• 1.7 vertical - 2.4 slant TEC unit accuracy (- 45 cm delay at L1 frequencies)

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Slant-Path TEC Maps
2-D maps of of slant path TEC over the CONUS for
each GPS satellite in view updated every 15
minutes
A
B
Sat. 1
Sat. 14
A
B
C
A
B
C
A
B
Sat. 29
C
Sat. 5
.etc
C
Applications 1. Ionospheric correction for
single frequency GPS 2. Support dual-frequency
integer ambiguity resolution for more rapid
decimeter and centimeter accuracy positioning
C
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Ionospheric correctors for NGS-OPUS in new RINEX
format
US-TEC slant TEC provides ionospheric correctors
for RINEX files
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VTEC Short-term Forecast
Using USTEC 10-day average to predict the
ionospheric behavior in to the next 1 to 2
hours.,
USTEC 10-day average
USTEC 15-min data
time
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Capture gradientsstationary walls of TEC
compromise integrity of LAAS
Courtesy Tom Dehel, FAA
TEC walls 130 TEC units over 50 km 20 m of
GPS delay walls move 100 to 500 m/s
wall
SED?
1 TEC ? 16cm delay at L1
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Situational awarenessTEC Gradients
Use information on TEC gradients to estimate time
interval needed to record dual-frequency GPS data
to achieve cm level positioning accuracy
quiet ionospheric conditions small gradients,
shorter intervals
disturbed ionospheric conditions - steeper
gradients, longer intervals
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Challenges Large Gaps in Global Coverage e.g.
African Equatorial Longitudes
Coster and Foster
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Sponsors NASA, NSF, EOARD, ICTP, AFRL, AFOSR,
ONR, CAWSES COSPAR
IHY-Africa Workshop
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Overview of Proposed Instrument Arrays
Overview of Instrument Arrays
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Canada
Expansion in global ground-based GPS networks
combined with space-based occultation to improve
global specification
Europe (EUREF)
USA
IHY-Africa
COSMIC occultations
JPL
South America
ocean buoys
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IGS Rapid Ionosphere ? Real-time Ionosphere
Manuel Hernandez-Pajares et al
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Future Direction

• Move from regional to multi-regional to global
  capability
• Move from 1000 real-time stations
• Modeling capability exists (e.g. JPL-GAIM, global
  USTEC, USU/AFWA-GAIM)
• Sparse real-time data
• Forge collaborations and partnerships
• Leverage IGS/ICG/UNCOPUOS and ISES
• What is the value of accurate real-time
  ionospheric maps for IGS applications?
• Natural consequence of improving accuracy of
  rapid iono maps and 2nd order corrections
• Maps of ionospheric irregularities

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The challenge in forecasting the ionosphere and
total electron content
1hr forecast 0.9 2 hr forecast 0.8
12hrs
24hrs
15 minute units
15 min intervals
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CHAMP (400 km) OSEC Halloween stormMannucci et
al. 2005
50m delay at L1
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Plasma Bubble Evolution

• Mesoscale Model
• Describes temporal development of plasma
  structure
• Uses nonlinear continuity and momentum equations
• Includes self-consistent electric fields
• Coupled to ambient background
• Estimates spectrum of density fluctuations
• Retterer (1999)

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Global Real-Time Network
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Customers

• High Frequency (HF) Communication
• ground-to-ground or air-to-ground communication
• establish accurate maximum useable frequencies
• support automatic link establishment systems
• e.g. civilian aviation, maritime, frequency
  managers
• Single Frequency Positioning and Navigation
• single frequency potential sub-meter accuracy
  positioning
• e.g. civil aviation, advanced vehicle tracking,
  potential for E911 improvements
• Dual Frequency Positioning and Navigation
• decimeter accuracy 10-50 cm
• e.g. real-time kinematic (RTK), autonomous
  transportation, off-shore drilling and
  exploration
• rapid centimeter accuracy positioning 1-2 cm
• e.g. surveyors, possible InSAR applications
• Satellite Communication
• specification and forecast of scintillation
  activity
• e.g. satellite operators, drilling companies